Category: The Certified News

A total collection of all blog posts, news updates and other information posted by The Certified News.

Posted on by

What New Research Reveals About Cannabis and Alzheimer’s Disease

2025 review of 45 studies shows how CBD acts on amyloid and inflammation in Alzheimer's. A 2026 clinical trial shows a THC/CBD combination easing dementia agitation.
Grace at the End — What New Research Reveals About Cannabis and Alzheimer's Disease | The Certified
The Grower's Connect
Research Deep Dive · Neurodegeneration

Stepping out of the growroom and into the clinic this week. We're pairing a 2025 review that maps everything the lab literature says CBD does inside an Alzheimer's brain, with a landmark clinical trial result reported at a major dementia research conference — literally yesterday — showing what a THC/CBD combination does for real patients at the end of life.

Neuroscience · Alzheimer's Disease · Clinical Trial News · 2025–2026

Grace at the End — What New Research Reveals About Cannabis and Alzheimer's Disease

A comprehensive 2025 review mapped 45 studies and 64 genes to show how CBD acts on the molecular hallmarks of Alzheimer's disease. A year later, the first randomized controlled trial of a THC/CBD combination in hospice-eligible dementia patients reported results — and they were significant, fast, and sustained.

The Grower's Connect  ·   ·  13 min read
45 studies reviewed, spanning nine biological pathways CBD affects in Alzheimer's models
64 genes CBD modulates, mapped onto five enriched biological pathways
120 hospice-eligible dementia patients in the first controlled trial of its kind
87.2% of treated patients improved by week 12, versus 23.6% on placebo
Listen to this article Grace at the End — What New Research Reveals About Cannabis and Alzheimer's Disease
Audio coming soon — replace this div with your <audio> tag when ready
Quick Answers & Key Takeaways
  • CBD's Action on Alzheimer's Biology: A 2025 review of 45 studies shows CBD influences amyloid-beta, neuroinflammation, and oxidative stress pathways.
  • The 2026 LiBBY Clinical Trial: The first Phase 2 randomized trial showed a THC/CBD combination significantly reduced agitation in hospice-eligible dementia patients within just 2 weeks.
  • Sustained Relief: By week 12, 87.2% of patients receiving THC/CBD showed clinical improvement in agitation compared to just 23.6% on the placebo.

Roughly half of people with dementia experience agitation in the final stage of the disease, when they become eligible for hospice care. Pacing. Calling out. Hitting, kicking or resisting care. Distress that a person nearing the end of their life often cannot put into words. For decades, clinicians treating this have had almost nothing built for the job — off-label antipsychotics, benzodiazepines and opioids, borrowed from other conditions, carrying real risks in a population that is already frail. There has never been a proper controlled trial testing an alternative in this specific group. Until this week.

On 14 July 2026, at the Alzheimer's Association International Conference in London, researchers presented topline results from the LiBBY trial — the first randomized, double-blind, placebo-controlled study of a THC/CBD combination in hospice-eligible dementia patients. The results were, in the words of lead investigator Jacobo Mintzer, a "robustly positive" step forward for a population that clinical research has largely overlooked. It lands almost exactly one year after a separate team in Brazil published the most complete map yet of what cannabidiol actually does, at a molecular level, inside an Alzheimer's-affected brain. Read together, the two papers tell a rare kind of story in medicine: the mechanism, and then the proof.

Why Alzheimer's Needs New Treatment Options

Alzheimer's disease is not one problem but several happening at once — amyloid-beta protein clumping between neurons, tau protein tangling inside them, chronic neuroinflammation, oxidative stress, and a slow collapse of the cholinergic signalling system the brain relies on for memory. The only widely used treatments, cholinesterase inhibitors, target just one piece of that puzzle, and their benefit is modest while their side effects — nausea, dizziness, cardiovascular complications — are not trivial, especially in older, frailer patients. A team at the Federal University of Paraná, Brazil, set out to systematically compile what the scientific literature actually says about cannabidiol as a candidate for filling that gap.

About the 2025 Review

The researchers searched PubMed and Web of Science for every paper matching "cannabidiol" and "Alzheimer's," with no date or study-type filter. Of 144 results, 45 original research articles survived screening to exclude reviews and papers that only mentioned the terms in passing. These 45 studies span in vivo, in vitro and in silico (computational) models, and together describe 61 distinct experimental outcomes across nine categories of Alzheimer's biology.

What 45 Studies Say CBD Does to an Alzheimer's Brain

Sorted by how much research attention each has received, five categories dominate the literature: amyloid-beta biology, behavioural changes, neuroinflammation, oxidative stress, and the cholinergic pathway.

Amyloid-β · 26.2% of Outcomes

CBD is linked to lower expression of the secretase enzymes that cleave amyloid precursor protein into Aβ fragments, and is described as a potential inhibitor of beta-secretase activity. In vivo models show reduced Aβ accumulation in the hippocampus and cortex, with CBD's ROS-scavenging ability proposed as one driver — less oxidative stress, less signal for Aβ production in the first place.

Neuroinflammation · 18% of Outcomes

Microglia, the brain's resident immune cells, switch between a resting state and an inflammatory one in response to Aβ. Studies show CBD blocking that transition, reducing pro-inflammatory cytokines and inducible nitric oxide synthase, and acting as an agonist at the PPAR-γ receptor to reduce inflammatory damage and promote new neuron growth in the hippocampus.

Oxidative Stress · 14.8% of Outcomes

Multiple cell and animal models show CBD reducing reactive oxygen species without triggering compensatory overexpression of oxidative-stress genes — protecting cells from oxidising agents and from methylglyoxal damage, and modulating mitochondrial dynamics genes disrupted by iron overload in neurodegeneration models.

Behaviour & Cholinergic Pathway · 18% + 8.2%

Across rodent AD models, CBD-treated animals consistently show better memory processing and exploratory behaviour than untreated controls. Separately, CBD reduces the activity of both acetylcholinesterase and butyrylcholinesterase — the same enzyme class current AD drugs target, but without their drug class's typical side-effect profile.

One human trial found that a daily three percent CBD regimen produced a significant improvement in behavioural and physiological symptoms of dementia, compared with conventional treatment — a rare piece of clinical, rather than preclinical, evidence in the whole dataset.

The Genetic Fingerprint of CBD

Beyond the narrative review, the team ran a computational analysis to see which specific genes CBD touches, and which biological pathways those genes belong to. Pulling from two studies that had measured gene expression changes after CBD treatment, they assembled a set of 64 CBD-modulated genes and tested it for pathway enrichment against the KEGG database — a standard bioinformatics technique for spotting whether a gene list clusters meaningfully around known disease pathways, rather than scattering randomly.

Five Pathways, One Signal

  • Alzheimer's disease pathway itself: genes tied to amyloid formation (PSEN1, PSEN2, BACE1, NCSTN) and neurodegeneration mechanisms clustered here, the strongest and most expected result.
  • Neurotrophin signalling: genes supporting neuron differentiation and maintenance, including kinase-signalling genes like AKT1 and the PIK3 family, which regulate cell survival and neurite growth.
  • Pathways of neurodegeneration — multiple diseases: a broader KEGG category capturing shared mechanisms — proteasome dysfunction, mitochondrial abnormalities — across several neurodegenerative conditions, not just Alzheimer's.
  • Lipid and atherosclerosis pathway: genes from the CAMK2 and heat-shock protein families, connecting CBD's action to lipid metabolism and to chaperone proteins that help prevent Aβ and tau aggregation.
  • Shigellosis — an unexpected fifth pathway: not an infection finding. This bacterial-infection pathway shares ubiquitination machinery with Alzheimer's protein-clearance mechanisms, and its appearance here reflects CBD's effect on ubiquitin-related genes rather than anything to do with dysentery.

Then the Real News — The LiBBY Trial

Everything above is preclinical or mechanistic — mice, worms, cell lines, gene lists. It is exactly the kind of evidence a 2025 review would flag as promising but incomplete, and the Brazilian team said so directly: current clinical evidence for CBD in Alzheimer's disease remains limited, most human studies combine CBD with other cannabinoids in ways that muddy interpretation, and there had been no randomized Phase III trial focused specifically on AD. That is the gap the LiBBY trial — Life's End Benefits of cannaBidiol and tetrahYdrocannabinol — was built to address, in the single symptom that causes the most suffering at the very end of the disease: agitation.

About the Trial

LiBBY was a multicenter, randomized, double-blind, placebo-controlled Phase 2 study run by the NIA-funded Alzheimer's Clinical Trial Consortium across multiple U.S. sites. It enrolled 120 hospice-eligible participants with Alzheimer's or another dementia and clinically significant agitation — mean age 80.5, 55% female, 58% from underrepresented ethnoracial groups. Participants received an oral THC/CBD formulation dissolved in digestible oil (a half dose of 2mg THC/100mg CBD twice daily for the first week, stepping up to a full dose of 4mg THC/200mg CBD twice daily for weeks two through twelve) or a matched placebo. Agitation was measured using the Cohen-Mansfield Agitation Inventory, a standard clinical scale.

The trial hit both its primary and key secondary endpoints, and the effect size was large by clinical-trial standards. At two weeks, the treatment group showed a 6.27-point greater reduction in agitation scores than placebo — a statistically significant, rapid effect. By twelve weeks, that gap had widened to an 8.23-point greater reduction, meaning the benefit wasn't just fast, it held. Clinician-rated global improvement told the same story from a different angle.

LiBBY — The Headline Numbers

  • Week 2 agitation reduction: 6.27 points greater in the THC/CBD group than placebo (p=0.0004).
  • Week 12 agitation reduction: 8.23 points greater in the THC/CBD group than placebo (p<0.0001), showing the effect was sustained, not fading.
  • Clinician-rated improvement, week 2: 83.9% of treated participants improved, versus 30.5% on placebo.
  • Clinician-rated improvement, week 12: 87.2% of treated participants improved, versus 23.6% on placebo.
  • Adverse events: similar overall rates between groups (46.7% treatment vs 42.4% placebo). Serious adverse events were more frequent in the treatment arm (23.3% vs 11.9%), though investigators determined none were related to the study medication.

Beyond the numbers, the investigators highlighted something just as important as the result itself: this population — hospice-eligible dementia patients, disproportionately excluded from clinical trials — could be recruited, enrolled and retained, including participants from historically underrepresented communities. Three-quarters of participants lived in community settings rather than institutions. Paul Aisen, one of the trial's principal investigators, called it proof that "high-quality clinical research can and should be conducted in people with advanced dementia," a population most drug development has simply passed over.

Reading These Two Papers Together

It's worth being precise about what connects these studies and what doesn't. The Brazilian review's molecular evidence is built almost entirely on isolated CBD — in mice, worms and cell lines, targeting amyloid, tau, inflammation and oxidative stress broadly across the disease course. LiBBY tested a THC/CBD combination, not CBD alone, in a single late-stage population, for a single symptom: agitation, not cognitive decline or amyloid burden. LiBBY doesn't confirm the amyloid or tau mechanisms the review describes, and the review's molecular story doesn't explain why adding THC specifically helped with agitation. What the two papers do together is bracket the picture — one showing plausible biology across the whole disease, the other showing a real clinical effect at one specific, brutal moment near its end.

What Neither Study Fully Answers

Both papers are honest about their own limits, and it's worth sitting with them rather than skipping past. The review's authors note that their gene-expression analysis rests on just two source studies and 64 genes — a starting map, not a finished one — and that their literature search, by design, excluded studies that examined CBD's mechanisms without explicitly tying them to Alzheimer's disease, which may have left relevant evidence out. More strikingly, they found no studies in their search that directly examined CBD's potential adverse effects or toxicity in the Alzheimer's context specifically — a genuine blind spot, given that CBD is known elsewhere in the literature to carry a dose-dependent risk of liver enzyme elevation and to inhibit several cytochrome P450 enzymes, raising real drug-interaction concerns in older patients typically on multiple medications.

LiBBY, for its part, is a Phase 2 trial, not the Phase 3 evidence typically required before a treatment becomes standard practice. It tested one specific dose, one specific population, and one specific symptom over twelve weeks — it says nothing about whether THC/CBD affects the underlying disease process, and the higher rate of serious adverse events in the treatment arm, even though unattributed to the drug, is a detail worth tracking rather than glossing over as the open-label extension phase reports its own results. Real answers about long-term safety, optimal dosing and disease-modifying potential are still ahead, not behind.

What This Actually Means Right Now

  • Not a Cure Neither paper claims CBD or THC/CBD reverses or halts Alzheimer's disease. The review documents plausible protective mechanisms; LiBBY documents symptom relief for agitation specifically, in the disease's final stage.
  • Complementary, Not Replacement The review's own authors position CBD as a possible complement to existing cholinesterase inhibitors, particularly for patients who tolerate current drugs poorly — not a substitute for them.
  • Different Products, Different Claims Most of the molecular evidence concerns isolated CBD. LiBBY's benefit is specifically for a defined THC/CBD combination at defined doses — the two are not interchangeable, and neither generalises automatically to over-the-counter CBD products of unknown composition.
  • A Population Finally Included Perhaps the most significant outcome of LiBBY, independent of the drug itself, is proof that hospice-eligible dementia patients can be safely and ethically enrolled in rigorous clinical trials — opening the door to more research in a group medicine has largely left behind.
  • Shared Decision-Making Still Applies The Alzheimer's Association's own response to these findings recommends non-pharmacological strategies as a first-line approach to agitation, with careful, individualised review of any pharmacological option alongside patients, families and clinicians.

What makes this pairing worth sitting with is the shape of the story, not just the numbers. A year ago, the honest scientific answer to "does CBD help with Alzheimer's" was: plausibly, mechanistically, in a lot of different ways, but nobody has properly tested it where it matters most. This week, for one of the disease's most distressing symptoms, in one of the populations medicine has most often excluded, somebody finally did.

Cannabis Research Coverage — The Grower's Connect

Source Study 1: Mello-Hortega JV, de Oliveira CS, de Araujo VS, Furtado-Alle L, Tureck LV, Souza RLR. Cannabidiol and Alzheimer Disease: A Comprehensive Review and In Silico Insights Into Molecular Interactions. European Journal of Neuroscience 2025, 62:e70229. doi:10.1111/ejn.70229 — Polymorphisms and Linkage Laboratory, Department of Genetics, Federal University of Paraná, Curitiba, Brazil. Received 9 May 2025; Accepted 2 August 2025.
Source Study 2: Mintzer J, et al. Topline Results From ,LiBBY Trial Show THC/CBD Combination Significantly Reduces Agitation for People With Dementia at End of Life. Presented at the Alzheimer's Association International Conference (AAIC) 2026, London, 14 July 2026. The Life's End Benefits of cannaBidiol and tetrahYdrocannabinol (LiBBY) study — Alzheimer's Clinical Trial Consortium, funded by the National Institute on Aging (R01AG068324-01) and the Alzheimer's Association. Presenting author: Jacobo Mintzer, M.D., Medical University of South Carolina / Ralph H. Johnson VA Healthcare System.
Posted on by

THE GHOST IN THE BOTTLE: HOW CBD TURNS ITSELF INTO THC, HHC AND CBN

cbd turns intself into thc
The Ghost in the Bottle — How CBD Turns Itself Into THC, HHC and CBN | The Certified
The Grower's Connect
Cultivation Science · Processing & Storage

Continuing the cultivation science arc. We have covered harvest timing, AI readiness tools, bud rot, and eight years of curing data. This week we look at something growers and processors rarely think about: what acid does to CBD, and why the same chemistry behind the "legal HHC" market can switch on by accident, in a bottle, with no lab involved.

Cultivation Science · Processing Chemistry · Cannabinoid Safety · Research 2023

The Ghost in the Bottle — How CBD Turns Itself Into THC, HHC and CBN

A 2023 study out of Kyung Hee University put isolated CBD into mildly acidic ethanol and simply waited. No catalyst, no pressure chamber, no intent to synthesise anything. Within hours, the CBD was gone — and eight new compounds had taken its place, several of them psychoactive.

The Grower's Connect  ·   ·  11 min read
8 new compounds detected from one sample of acid-treated CBD
95% of CBD degraded within 5 hours at pH 2.0 and 70°C
pH 5.0 the threshold below which degradation barely happens at all
16 cannabinoids identified across every condition tested in this study
Listen to this article The Ghost in the Bottle — How CBD Turns Itself Into THC, HHC and CBN
Audio coming soon — replace this div with your <audio> tag when ready

Quick Answer: Can CBD Convert to THC or HHC?

  • Yes, CBD can convert to THC: Research confirms that exposing CBD to mildly acidic conditions (pH 2.0 to 3.5) causes it to naturally degrade into Delta-9 and Delta-8 THC.
  • HHC Formation: Without an industrial lab, acid-treated CBD dissolved in ethanol can undergo solvent addition to form ethoxy-HHC or methoxy-HHC analogs.
  • Storage Matters: Products formulated with citric acid (like gummies) or stored in warm environments accelerate this CBD degradation process.

Human stomach acid sits somewhere between pH 1.5 and pH 3.5. That is not a coincidence for this article — it is close to the exact range a team of South Korean researchers chose when they set out to answer a question the CBD industry has mostly avoided asking directly: what actually happens to cannabidiol when it sits in an acidic environment for a while? Not in a clandestine lab with a hydrogen tank and a palladium catalyst, but in the ordinary acidic conditions a CBD product might encounter — a citrus-flavoured gummy, a vinegar-preserved tincture, a bottle that got warm in transit, or simply a stomach after being swallowed.

The answer, published in the Journal of Food and Drug Analysis in 2023 by a team from Kyung Hee University, Kookmin University and Woosuk University, is not reassuring. Isolated CBD dissolved in ethanol and mildly acidified with hydrochloric acid began converting — on its own, at temperatures as low as 30°C — into a small chemistry set of psychoactive compounds. Delta-9 THC. Delta-8 and delta-10 THC. Cannabinol. Cannabichromene. And a family of alkoxy-substituted compounds the researchers themselves describe as HHC analogs.

Why CBD to HHC Conversion Matters for Cannabis Processors

We have written before about hexahydrocannabinol and the vape-shop version of the "legal high" argument — a semi-synthetic cannabinoid made by hydrogenating CBD under a metal catalyst and high pressure, deliberately, in an industrial setting. This study asks a different and in some ways more unsettling question: does CBD need a lab to start moving in that direction at all? The double bond that commercial HHC producers saturate with hydrogen gas turns out to be reactive enough that it will also react with whatever solvent it happens to be sitting in, given nothing more than acid and time. No catalyst required. No intent required.

About the Method

The researchers isolated 85 milligrams of pure CBD from cannabis inflorescence, dissolved it in ethanol, and adjusted the solution to pH 2.0, 3.5 or 5.0 using dilute hydrochloric acid. Samples were incubated at 30°C, 50°C or 70°C for periods ranging from one hour to twenty-four hours, then chemically tagged (a process called trimethylsilyl derivatisation) and run through gas chromatography–mass spectrometry, an analytical technique that separates and identifies individual compounds in a mixture by their mass fragments. This let the team track exactly how much CBD remained and exactly what it had turned into, at every combination of acidity, heat and time.

The Acid Degradation Pathway: How CBD Converts to THC and HHC

The transformation is not random. It follows a small number of well-defined chemical pathways, all starting from the same first step: acid activates the double bond in CBD's side chain, forming a positively charged carbon centre that is desperate to react with something.

Ring Closure → Delta-9 THC

The charged carbon reacts with CBD's own phenol group, folding the molecule closed into a new ring. This is the classic pathway to delta-9 THC, and it was the dominant early product in this study's ethanol solutions — the same reaction proposed to explain why CBD can convert to THC in simulated gastric juice.

Isomerisation → Delta-8 / Delta-10 THC

Once formed, delta-9 THC is not the end of the story. Continued acid exposure shifts the position of its double bond, producing delta-8 THC and delta-10 THC as minor but persistent by-products that kept accumulating for the full twenty-four hours tested.

Solvent Addition → Ethoxy/Methoxy-HHC

Instead of closing back into the ring, the charged carbon can instead grab a piece of the solvent itself — ethanol or methanol. The result is a hexahydrocannabinol-analog structure: the same skeleton commercial HHC is built on, but with an ethoxy or methoxy group sitting where a second hydrogen atom would normally go.

Oxidation & Ring Rearrangement → CBN and CBC

Separately, delta-8 THC can lose two hydrogen molecules to aromatise into cannabinol, while a distinct ring-opening and re-closing sequence produces cannabichromene. CBC's formation from acid-treated CBD had not been reported before this study.

Below pH 5.0, cannabidiol barely moves — even after twenty-four hours at seventy degrees Celsius. Push the same solution to pH 2.0, and it is largely gone within five hours.

The pH Threshold: At What Acidity Does CBD Degrade?

Of everything the study measured, acidity turned out to matter more than heat or time. At pH 5.0, essentially no degradation occurred, regardless of how hot or how long the reaction ran. At pH 3.5, degradation became measurable within five to ten hours. At pH 2.0, it was fast: roughly ninety-five percent of the CBD was gone within five hours at 70°C, and none remained detectable by the ten-hour mark. Delta-9 THC itself followed the same arc — it rose quickly, peaked around the five-hour point, and then began falling as it was further converted into ethoxy-HHCs, isomerised THCs and other products. A product tested once, early, would show clean CBD. Tested again later in its shelf life, it might not.

What The Numbers Actually Showed

  • pH 5.0, any temperature, 24 hours: no meaningful CBD degradation observed. This was the clearest safety margin in the entire dataset.
  • pH 3.5, 70°C: degradation and THC formation both increased steadily over the first ten hours.
  • pH 2.0, 30°C: degradation still occurred, just slower — acid alone, without much heat, was enough to start the reaction.
  • pH 2.0, 70°C: the fastest condition tested. CBD fell first-order over the first five hours; by ten hours it had disappeared from the chromatogram entirely.
  • Reaction solvent matters: in methanol instead of ethanol, the same pathway produced methoxy-HHC analogs instead of ethoxy ones — direct evidence that the solvent itself becomes part of the final molecule.

8 Psychoactive By-Products Formed from CBD Acid Degradation

At the most acidic, hottest, longest condition tested — pH 2.0, 70°C, twenty-four hours — the researchers identified eight distinct transformed products in a single reaction. Cannabichromene, delta-9 THC, and two ethoxy-HHC isomers were the major components. Delta-8 THC, delta-10 THC, cannabinol and a hydroxy-HHC derivative showed up as minor components. Across the full study, including parallel experiments on whole cannabis extract, the team catalogued sixteen cannabinoids in total — among them eight compounds structurally classed as THC isomers, all considered potentially psychoactive, alongside CBN and the methoxy- and ethoxy-HHC analogs.

Some of these were confirmed against authentic reference standards — THC isomers, CBC and CBN all matched known compounds exactly on retention time and mass spectrum. The HHC analogs and the hydroxy-HHC derivative were identified more tentatively, by matching chromatographic behaviour and interpreting their fragmentation patterns, because no commercial reference standards exist for them yet. That is itself a telling detail: these are compounds well-resourced analytical labs cannot buy a certified standard for, let alone the average processor trying to test a finished product.

The Ghost Doesn't Need A Lab

Commercial HHC is made deliberately — CBD is bombarded with hydrogen gas under a metal catalyst and pressure, in a controlled industrial process. This study shows a much lower bar gets you partway to the same neighbourhood of chemistry. Ordinary acid, ordinary ethanol, and time are enough to start converting that same reactive double bond — not into hydrogenated HHC itself, but into closely related alkoxy- and hydroxy-substituted cousins, plus a full slate of THC isomers and CBN. The synthetic ghost from the vape shop can, under the wrong storage conditions, start forming quietly in a bottle nobody meant to synthesise anything in.

Best Practices for CBD Processing and Storage to Prevent Degradation

None of this is abstract chemistry for growers who stop at flower. But for anyone extracting, formulating, bottling or storing CBD products — which is an increasing share of the South African cannabis economy — this study has direct, practical teeth.

Applied Implications for Manufacturers

  • Acidic Formulations CBD gummies and beverages acidified with citric or malic acid, or tinctures preserved with vinegar or low-pH alcohol, sit within the reactive window this study demonstrates. Checking and logging the actual pH of a finished formulation — not just the raw extract — is worth doing, especially for products with a long intended shelf life.
  • Heat in Transit The study shows degradation still proceeds, just more slowly, at 30°C — an ordinary hot day in a delivery vehicle or a warehouse without climate control. Time and mild heat compound the effect of any residual acidity in a product.
  • Residual Extraction Acids Processes that use acid catalysts or acidic wash steps during extraction or winterisation need thorough neutralisation. Incompletely neutralised residues left in a finished oil are a slow-motion version of exactly the reaction this study ran deliberately.
  • Oral Ingestion This isn't only a shelf-life question. The paper's own introduction cites earlier research showing CBD converts toward THC and related cannabinoids in artificial gastric juice — an environment in the same pH range tested here. Swallowing CBD oil exposes it, briefly, to comparable conditions inside the body.
  • Testing Blind Spots Routine potency testing usually screens for CBD and THC at a single point in time. It will not catch a product that starts clean and slowly accumulates HHC analogs, THC isomers or CBN across months on a shelf, because most labs are not set up to look for compounds that do not yet have certified reference standards.

What the Study Does Not Resolve

The authors are candid about the limits of their own data. The ethoxy-HHC, methoxy-HHC and hydroxy-HHC identifications are tentative — inferred from retention behaviour and mass spectral interpretation rather than confirmed against authentic standards, because none exist commercially for these specific compounds. The psychoactivity of the ethoxy-HHC derivatives specifically is, in the authors' own words, still controversial and not fully studied; their pharmacological profile has not been directly tested in the way delta-9 THC's has.

The experiments also used isolated CBD at fairly high purity, dissolved in pure ethanol or methanol — a simplified system, not a direct stand-in for the complex matrix of a real gummy, beverage or emulsified tincture, where other ingredients could accelerate, slow, or otherwise change these reactions. And while the pH and temperature ranges tested were chosen to be systematic, they are a controlled screen, not a simulation of any one product's actual storage history. What the study firmly establishes is that the chemistry is real and follows predictable, mechanistically explainable pathways — not whether any specific commercial CBD product on a shelf right now has crossed into psychoactive territory.

What it does put to rest is the idea that CBD is chemically inert once it leaves the plant. Given the wrong pH, it very much is not — and the compounds it becomes are not obscure novelties. They are the same THC isomers, the same CBN, and structural cousins of the same HHC that the market has spent the last few years arguing about.

Cannabis Research Coverage — The Grower's Connect

Source Study: Jeong M, Lee S, Seo C, Kwon E, Rho S, Cho M, Kim MY, Lee W, Lee YS, Hong J. Chemical transformation of cannabidiol into psychotropic cannabinoids under acidic reaction conditions: Identification of transformed products by GC-MS. Journal of Food and Drug Analysis 2023, 31(1), Article 11, 165–176. doi:10.38212/2224-6614.3452 — College of Pharmacy, Kyung Hee University; Graduate School of Techno Design, Kookmin University; College of Pharmacy, Woosuk University, Republic of Korea. Received 16 August 2022; Published online 15 March 2023.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

THC Degradation & Cannabis Curing

THC Degradation & Cannabis Curing: What Time Actually Does to Your Cannabinoids
THC Degradation & Cannabis Curing: What Time Does to Cannabinoids
The Grower's Connect
Cultivation Science · Post-Harvest

Continuing the cultivation science arc. We have covered harvest timing, AI readiness tools, and what bud rot does to your cannabinoids. This week we look at what happens after the cut — the science of cannabinoid change over time, finally mapped with 8 years of real data.

Post-Harvest Science · Cannabinoid Chemistry · 2025 Research

THC Degradation & Cannabis Curing: What Time Actually Does to Your Cannabinoids

Growers have guessed at the perfect cure for decades. A 2025 study tracked 150 cannabis samples across 8 years of storage — building the first precise model of exactly how THC degrades, CBD changes, and CBN forms over time.

The Grower's Connect  ·  2025  ·  12 min read
−99% THC remaining after 8 years — falling from 35.16% down to 0.44%
2 years The exact inflection point when CBD and CBN peak before declining
R²=0.99 Accuracy of the new model predicting storage age from cannabinoid ratios
150 Resin samples analysed — the longest cannabis storage study to date
Listen to this article THC Degradation & The Science of the Cure
Audio coming soon — replace this div with your <audio> tag when ready

Article Quick Summary: Cannabinoid Storage & Degradation

  • Rapid THC Loss: THC degradation happens fastest in the first 24 months of storage, with over 90% of the psychoactive compound breaking down by year two.
  • The 2-Year CBN Peak: As THC degrades via oxidation, it converts to CBN (Cannabinol). CBN reaches its absolute peak therapeutic concentration exactly at the two-year storage mark.
  • CBD Fluctuations: CBD levels actually rise during early storage (as CBDA decarboxylates) before slowly degrading after the two-year inflection point.
  • Yield Collapse: Storing cannabis long-term doesn't just change the chemical profile; it drastically reduces extractable yield (crude resin) by up to 87%.

Ask a grower how long they cure their cannabis, and you'll get as many answers as there are growers. Eight weeks. Six months. A year. Some swear by extended cures, claiming a smoother smoke and a heavier, more medicinal effect. Others chase the freshest possible harvest to preserve volatile terpenes. Almost none of them have hard data.

The transformation that happens inside curing cannabis — specifically THC degradation, the accumulation of CBN, and the shifting of the whole cannabinoid profile — has been one of the most poorly understood processes in cultivation. Not because it isn't important, but because studying cannabis shelf life properly requires years of patience and a very large sample set.

A team from Morocco's Forensic Sciences Institute of the Royal Gendarmerie and the University of Sidi Mohammed Ben Abdellah did exactly that. Published in Scientific Reports in 2025, their study analysed 150 cannabis resin samples seized from the Rif Mountains and stored under forensic archiving conditions for periods ranging from fresh up to eight years.

Using gas chromatography, they measured THC, CBD, and CBN concentrations at five distinct storage points — zero, two, four, six, and eight years — and built mathematical models that can predict cannabinoid content based on storage time. They can tell you, with near-certainty, exactly what time does to your weed.

Cannabis Storage Research: Why This 8-Year Study Changes Curing

Previous research on cannabinoid stability and THC degradation typically followed samples for one to four years. The authors note that an eight-year dataset of this scale is unprecedented in published literature. This matters because the behaviour of cannabinoids over time is not linear.

As the study demonstrates clearly, THC degrades rapidly in the first two years, then the rate of loss slows down. CBD and CBN rise simultaneously, peak, and then fall. The long-term endpoint of the curing process is very different from what you see at the two-year mark. Short studies can only see one part of the curve.

About the Sample Type

This study used compressed cannabis resin — hashish — rather than whole flower. Resin is produced from the exact same glandular trichomes that cover cannabis inflorescences. The cannabinoid chemistry is directly comparable to what happens in cured flower, and the degradation pathways (THC to CBN conversion) are identical. Storage conditions were dark, dry, at ambient temperatures (20–25°C) in sealed bags — conditions analogous to a well-maintained curing environment.

The Curing Timeline: What Happens to THC, CBD, and CBN Year by Year

The clearest way to understand how long to cure cannabis — and what happens if you store it too long — is to walk through the data chronologically. The researchers measured average values for each cannabinoid at each storage point. What emerges is a story that plays out in three distinct phases.

Fresh — Unstored

THC Dominates, CBD and CBN Are Minor

Fresh resin showed the highest overall extraction yield at 37.9% ± 1.45% of dry weight. THC concentration sat at 35.16% ± 3.87% — dominant and high. CBD was present at 3.92%, and CBN at a low baseline of 0.87%. This is the profile of a plant that has just been harvested: THC is fully intact, CBN formation has barely started, and CBD is present as a minor component. This is also the point at which the cannabis yields the most extract.

2 Years

The First Major Shift — THC Crashes, CBD and CBN Peak

The two-year mark sees the most dramatic single change in the entire dataset. THC falls to 2.74% — a loss of more than 90% of its initial concentration. At the same time, CBD rises to 6.71% (its highest point across any storage period) and CBN reaches 6.94% (also its absolute peak). The THC/CBN ratio, which starts extremely high in fresh material, has inverted completely. This is the crucial inflection point of cannabis storage.

4 Years

Continued THC Degradation, CBD and CBN Decline

THC continues falling to 2.24%. CBD drops back to 5.58%, and CBN slightly lowers to 6.51%. The peak of CBD and CBN observed at the two-year mark is not maintained forever — both cannabinoids begin their own slow degradation once the precursor THC has largely depleted. The profile is now dominated entirely by CBD and CBN, with THC left as a minority cannabinoid.

6 – 8 Years

Total Cannabinoid Depletion Accelerates

At six and eight years, THC levels drop to negligible amounts. In the eight-year sample, THC measured just 0.44% — less than 1.5% of its original concentration. CBD reaches its minimum at 1.76%, and CBN at 2.94%. Extraction yield reaches its floor at 5.10%, compared to 37.9% when fresh. The chemical complexity of aged cannabis accumulates as known cannabinoids break down into unidentified degradation compounds.

The Mechanism: Why THC Degrades into CBN During Storage

Understanding why weed loses potency matters as much as knowing when it happens. The researchers confirm what the biochemistry literature had already proposed, and extend it with the longest dataset yet assembled.

THC to CBN Oxidation

THC degrades primarily through oxidation. The mechanism involves the formation of intermediate hydroxylated derivatives before final conversion to CBN (Cannabinol). This process follows first-order kinetics — meaning the rate of loss is proportional to how much THC remains. Heat and oxygen exposure accelerate this conversion significantly.

Why CBD Also Rises, Then Falls

CBD's concurrent rise with CBN during the first two years is not a direct product of THC degradation. Instead, both CBD and CBN increase together during early storage because CBDA (the acid precursor) decarboxylates slowly over time to release free CBD. After two years, CBD itself begins to degrade through a slower oxidative pathway.

Extraction Yield Collapse

The extraction yield falls from 37.9% to 5.10% over eight years — an 87% reduction. The researchers point to additional mechanisms beyond cannabinoid loss: volatilisation of terpenes, adsorption of cannabinoids to packaging, and the formation of polymeric degradation compounds that are no longer soluble.

What Happens to Everything Else

GC/FID analysis measures only THC, CBD, and CBN. Aged samples accumulate a large number of unidentified peaks — cannabinoid isomers and oxidised derivatives (including Δ⁸-THC). The known cannabinoids do not account for all the mass lost from THC, which is why CBN accumulation alone cannot explain the full scale of THC disappearance.

"At two years of storage, CBD and CBN have both reached their highest concentrations — while THC has lost more than 90% of its original level. The plant's chemistry has been effectively inverted by time and oxygen alone."

Predicting Cannabinoid Degradation: Calculating THC Loss Over Time

Building predictive models was the second major objective of the study, and this is where forensic science meets grower utility. The team developed two classes of model: one that predicts cannabinoid content from storage time, and one that works in reverse — predicting how long cannabis has been stored based on its cannabinoid profile.

The researchers found that the cubic regression model outperformed all others when tracking THC, CBD, and CBN. The cubic model achieved validation R² values of 0.999 for THC, perfectly capturing the multi-phase behaviour of stored cannabis: rapid early change, a transitional period, and a slow long-term decline.

The Cubic Degradation Equations — Reading the Math

  • THC (%): = 3.30 − 0.10 × (years) + 0.055 × (years)² − 0.005 × (years)³. THC falls rapidly from the start, but the cubic term means the rate of loss slows down at higher storage durations — the curve flattens as THC approaches zero.
  • CBD (%): = 10.35 − 0.28 × (years) − 0.0157 × (years)² + 0.0007 × (years)³. CBD starts high, declines across all time points, with a steepening decline in mid-storage before flattening at the long-term tail.
  • CBN (%): = 8.72 − 0.123 × (years) − 0.024 × (years)² + 0.0005 × (years)³. CBN's curve shows a similar shape to CBD — a starting peak that declines over extended storage, with the cubic term capturing the very slow long-term degradation tail.
What This Means for Growers

If you know how long you have been curing your harvest, you can use these exact curves to estimate where your cannabinoid profile now sits. You can determine if the direction of change is still working in your favour, or if your weed has moved past the point of peak therapeutic value. The two-year inflection point — where CBD and CBN peak and then begin declining — is your ultimate reference mark.

How to Cure Cannabis: What This Means for Your Storage Strategy

The study was designed for forensic scientists, but the data speaks directly to decisions that every grower makes regarding their curing jars. Here is what the findings imply for your post-harvest cultivation practice.

Applied Implications for Curing & Storage

  • The Two-Year Mark If your goal is maximum CBN content — highly sought after for its sedative, analgesic, and anti-inflammatory properties — long-term storage up to the two-year mark is the ultimate strategy. Storing beyond two years does not accumulate more CBN; it begins to deplete it.
  • CBD and the Cure CBD rises during early storage and peaks at the two-year point. This suggests that for CBD-dominant cultivars, there is a genuine, mathematically proven benefit to extended curing far beyond the standard 4–8 week window.
  • THC and the Cure For THC-dominant cultivars, this study is unambiguous: THC degrades fast and early. Over 90% of the drop occurs within the first two years. Shorter, well-managed cures in dark, sealed, cool conditions can slow this oxidative process, but they cannot stop it entirely.
  • CBN/THC Ratio The ratio of CBN to THC is a reliable indicator of how long cannabis has been stored. Fresh material has a very low CBN/THC ratio; aged material has an inverted one. Tracking this ratio across lab tests during curing is incredibly informative.
  • Strategic Medicine Deliberate long-term storage of cannabis can be used strategically to enhance therapeutic value by allowing THC to fall while CBD and CBN accumulate. For medicinal producers targeting non-psychoactive profiles for sleep and pain, a two-year cure is not spoilage — it is a precise production method.
The Extraction Yield Problem

The 87% drop in extraction yield over eight years is a stark reminder that cannabinoid percentages tell only part of the story. If you are making extracts or concentrates from long-stored flower, the cannabinoid ratios may look favourable on paper (high CBN) — but the total mass of extract you can recover from a given weight of material drops substantially with time.

What this study establishes, firmly and for the first time across an eight-year arc, is the exact shape of the cannabinoid degradation curve. The days of guessing what time does to your cannabinoids are officially over.

Frequently Asked Questions About Cannabis Storage & Degradation

Does weed lose potency over time?

Yes. Cannabis loses potency (specifically THC) over time through a process called oxidation. Research shows that THC degrades rapidly within the first 24 months of storage at ambient temperatures, potentially losing up to 90% of its original concentration if not stored in optimal, airtight, cold conditions.

Does old weed turn into CBN?

Yes. As THC is exposed to oxygen and ambient heat over time, it degrades and converts directly into Cannabinol (CBN). CBN is a mildly psychoactive cannabinoid known for its heavy, sedative properties. The highest concentration of CBN in stored cannabis typically occurs around the two-year mark.

How long should you cure cannabis for the best results?

The ideal curing time depends on your goals. For maximum THC preservation and fresh terpene profiles, a standard 4 to 8-week cure in airtight jars (burped regularly) is optimal. However, if you are looking to create a highly sedative, CBN-rich medicinal product, curing and storing the cannabis for up to two years will maximize CBN and CBD levels while lowering THC.

Cannabis Research Coverage — The Grower's Connect

Source Study: Fettoukh N, Fadil M, Stambouli H, EL Bouri A, Bouyoun T, Annemer S, Boukhaled A, Farah A. Chemometric and predictive modeling of long term cannabinoid transformation in stored Cannabis sativa resin. Scientific Reports 2025, 15, 33827. doi:10.1038/s41598-025-03888-7 — Forensic Sciences Institute of Royal Gendarmerie, Rabat, Morocco; Laboratory of Applied Organic Chemistry, University Sidi Mohammed Ben Abdellah, Fez, Morocco. Received 1 March 2025; Published online 30 September 2025.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

Cannabis Bud Rot: The Rot You Don’t See Until It’s Too Late

cannabis bud rot
Cannabis Bud Rot (Botrytis): What Grey Mould Does to Trichomes & Cannabinoids
The Grower's Connect
Cultivation Science · Disease

Continuing our cultivation science arc. The last two weeks explored how to read harvest readiness. This week we look at what happens when a fungal pathogen gets there first — and what it does to the trichomes and cannabinoids before you even notice it.

Cannabis Pathology · Trichome Science · 2026 Research

Cannabis Bud Rot: The Rot You Don't See Until It's Too Late

Bud rot doesn't just destroy yield. A 2026 preprint from India documents what Botrytis cinerea actually does inside your flower — collapsing trichome structure, wiping out CBD, and rewriting the plant's cannabinoid chemistry from the inside out.

The Grower's Connect  ·  2026  ·  11 min read
−91% CBD collapse in field-infected plants (1.87% to 0.16%)
+117% THC increase in infected plants (1.04% to 2.25%)
20°C / 94%RH The peak trigger conditions for Botrytis spore production
7 days Time required for complete bud colonisation in high humidity
Listen to this article The Rot You Don't See Until It's Too Late
Audio coming soon — replace this div with your <audio> tag when ready

Article Quick Summary: What Bud Rot Does

  • Structural Damage: Botrytis cinerea physically crushes and destroys the capitate-stalked trichomes where cannabis stores its resin.
  • Cannabinoid Shift: Infection causes a catastrophic drop in CBD levels (up to 91% reduction) while simultaneously doubling THC levels, creating massive compliance risks.
  • Terpene Loss: Essential therapeutic terpenes, notably Myrcene and Limonene, see reductions of up to 79% in infected buds.
  • Hidden Infection: Spores colonize the deep vascular tissue of the bud days before grey mould becomes visible on the surface or during the curing process.

Most cannabis growers who have dealt with bud rot (Botrytis cinerea) describe the same devastating experience. You're a week or two from harvest. The flowers look dense, healthy, and frosted with trichomes. Then you find it — a patch of grey-brown fuzz buried inside a cola, or a single bract that crumbles when you touch it. By the time grey mould is visible on the surface, it has already been inside the flower for days, possibly weeks. The damage is done.

What that damage actually looks like — chemically, structurally, at the level of the trichomes themselves — has never been fully documented. Growers have known for years that infected buds smell wrong, smoke harsh, and test lower for potency. But the precise mechanism, and the specific changes to the cannabinoid and terpene profile that infection causes, had not been studied in a controlled scientific setting. Until now.

A preprint posted to Research Square in February 2026 by researchers at CSIR-Central Institute of Medicinal and Aromatic Plants in Lucknow, India, reports the first characterisation of Botrytis cinerea infecting cannabis. More importantly, it provides the first direct measurement of what that infection does to trichome structure, cannabinoid content, and terpene profiles. The findings are unsettling, and directly relevant to anyone growing CBD-dominant or medicinal cannabis.

What is Botrytis Cinerea (Bud Rot) in Cannabis?

Botrytis cinerea is the causal agent of grey mould, universally known to cultivators as cannabis bud rot. It is a necrotrophic fungal pathogen, meaning it actively kills the host tissue it colonises rather than living within it subtly. Ranked the second most economically damaging fungal pathogen globally, it attacks over 200 plant species. Cannabis is not a special case; it is simply another highly vulnerable host.

The pathogen enters cannabis inflorescences primarily through airborne conidia — microscopic spores that are always present in the environment, whether in outdoor field conditions, indoor grow tents, greenhouses, or post-harvest drying spaces. What makes cannabis particularly susceptible is the nature of late-stage flowers: dense, moisture-retaining, and covered in glandular trichomes that the fungus exploits as entry points and nutrient sources.

Why the Curing Jar Is Not Safe

Botrytis spores persist in harvested and drying flowers. The curing environment — enclosed, slightly humid, and warm — provides the exact conditions needed to reactivate latent infections. Growers who find rot in the jar are not seeing a new contamination event; they are witnessing the final stage of an infection that began invisibly weeks earlier in the grow room.

What Causes Bud Rot? The Ideal Conditions for Botrytis Spores

To effectively prevent bud rot, cultivators need to understand environmental triggers. The Indian research team mapped the exact environmental conditions under which B. cinerea produces the most spores on cannabis inflorescences. This matters because spore load drives infection pressure — the more conidia in the air, the faster an outbreak spreads through your canopy.

Environmental Triggers for Grey Mould

  • Peak Danger Zone: Maximum spore production occurred at 20°C combined with 94% relative humidity (RH). This is the exact microclimate growers must avoid during late flower.
  • Humidity Dominates: Peak conidial counts at 94% RH reached 12.30 × 10⁶ conidia per gram — roughly five times the count observed at 60% RH. Humidity is the dominant variable.
  • Temperature Ranges: The optimal temperature range for the fungus is 15–20°C. Hot, dry conditions (30°C) suppress the pathogen, which is why bud rot is predominantly an autumn or late-season problem.
  • Cold Protection: At 10°C, essentially no spores were produced. Cold curing environments (below 15°C) with humidity below 60% are genuinely protective — confirming popular cultivator wisdom.
  • Speed of Infection: Under high humidity, complete bud colonisation occurred within just seven days of inoculation.

The practical takeaway: if your late-flower environment sits between 15°C and 25°C with a relative humidity above 85%, you are running conditions that maximise Botrytis infection success. The dense, tightly packed colas that yield the most weight are the exact structures that trap moisture and create these dangerous micro-climates.

Trichome Damage: How Botrytis Destroys Cannabis Resin

This is where the research breaks genuinely new ground. Using scanning electron microscopy, the team visualised the interaction between B. cinerea and the trichome structures of infected cannabis tissue. What they found describes a systematic dismantling of the very biological factories responsible for cannabinoid and terpene production.

Cannabis flowers carry three types of trichomes, but the capitate-stalked trichomes — the large, mushroom-shaped glands that produce the bulk of the plant's resin — were the most severely affected. Under the electron microscope, infected tissue showed:

Surface Colonisation

Extensive mycelial growth blankets the bud surface, with spore-bearing stalks growing directly from the bract tissue. The fungal mass physically displaces and crushes delicate trichomes.

Deep Vascular Invasion

The pathogen is not confined to the surface. Mycelial filaments penetrate deep into the central vascular core (xylem and phloem). This is a systemic tissue infection, not mere surface mould.

Trichome Deformation

Glandular trichomes are visibly disrupted and trapped within mycelium. The characteristic round secretory heads — which contain the valuable oils — are completely collapsed or missing.

Density Reduction

Trichome density on infected bract tissue is markedly lower than on healthy tissue. Fungal colonisation actively reduces the number of functional trichomes left on the plant.

The researchers propose a two-fold mechanism of destruction: direct physical crushing of trichomes by fungal growth, and indirect disruption of biosynthesis pathways. The plant essentially reprograms its own chemistry in a failed attempt to fight off the infection.

"The pathogen colonises the very factory that produces the plant's most valuable compounds — and the disruption is not subtle. It is a comprehensive dismantling of trichome integrity."

Cannabinoid Changes: Bud Rot Drops CBD and Increases THC

The High-Performance Liquid Chromatography (HPLC) chemical analysis is where the data becomes alarming for anyone producing medicinal hemp or CBD-dominant cannabis. The numbers reveal a dramatic, consistent chemical transformation inside the rotting bud.

Chemical Profile Shifts (Infected vs. Healthy)

  • Total CBD (Field): Crashed from 1.87% in healthy plants to 0.16% in infected plants — a devastating 91% reduction.
  • Total CBD (Greenhouse): Collapsed from 1.41% to just 0.03% — a 98% reduction. Greenhouse infections proved catastrophically damaging to CBD.
  • Total THC (Field): Increased from 1.03% in healthy plants up to 2.25% in infected plants — more than doubling the psychoactive compound.
  • Total THC (Greenhouse): Rose from 0.82% to 1.29% in infected plants. This directional shift (CBD down, THC up) was entirely consistent.

This directional shift is not a coincidence. Both CBD and THC share the same biosynthetic precursor pathway (CBGA) within the glandular trichomes. The researchers suggest the fungal infection interferes with the enzymatic steps controlling this pathway, driven by oxidative stress and the pathogen's toxic secondary metabolites (botrydial and botcinic acid).

The Compliance Risk for Hemp Growers

For commercial hemp cultivators, this finding is a major compliance risk. A CBD-dominant plant running at 1.87% CBD and 1.04% THC in healthy tissue shifts to 0.16% CBD and 2.25% THC under infection. This creates potentially illegal, "hot" non-compliant flower, destroyed crop value, and regulatory headaches — all caused by an invisible fungus.

Terpene Loss: How Grey Mould Destroys Cannabis Aromas

Gas Chromatography (GC-MS) analysis completes the picture of what cannabis bud rot truly costs. Measuring thirteen significant terpene compounds, researchers confirmed that the loss of structural trichomes directly correlates to a massive loss of therapeutic aromas.

Terpene Destruction by Botrytis

  • Myrcene: Fell from 5.78% to 1.20% in infected plants — a 79% reduction. Myrcene is critical for the "entourage effect" and anti-inflammatory properties.
  • Limonene: Dropped precipitously from 37.07% to 4.46% in greenhouse-infected plants, the largest absolute reduction of any measured compound.
  • β-Caryophyllene: Reduced from 18.54% to 13.22%. This sesquiterpene showed slight resilience but still suffered meaningful losses.

Non-infected plants presented a classic therapeutic profile: high Limonene, significant Myrcene, and strong β-Caryophyllene. Infected plants presented a distorted, hollowed-out version of this profile, stripping the flower of its medicinal value and bag appeal.

How to Prevent and Manage Cannabis Bud Rot

While this study focused on pathology, the data provides a clear roadmap for cultivators looking to prevent bud rot and protect their canopy.

Applied Cultivation Strategies

  • VPD & Humidity Control The danger zone is 15–20°C with RH above 90%. Keep your late-flower relative humidity strictly below 55% to suppress the pathogen's reproductive capacity. A single night of heavy condensation can trigger an outbreak.
  • Airflow Architecture Botrytis disperses via airborne spores. Stagnant air pockets inside dense, tightly formed colas create high-humidity micro-environments. Defoliation and aggressive under-canopy airflow are non-negotiable.
  • Early Scouting By the time you see the grey fuzz, the fungus has already penetrated the vascular tissue. Look for early symptoms: a single yellowing sugar leaf, a dark/soft bract, or an off-putting smell from an otherwise healthy cola.
  • Accelerate Harvest Because infection rapidly destroys CBD and alters THC, allowing an infected crop to finish its cycle compounds the damage. If an outbreak cannot be contained, harvesting early is chemically supported to save remaining cannabinoids.
  • Post-Harvest Hygiene Dry your cannabis in environments below 15°C and under 55% RH. Inspect curing jars daily during the first week. Curing at 60%+ RH in warm rooms will rapidly accelerate latent Botrytis spores.

Frequently Asked Questions About Cannabis Bud Rot

Can you smoke weed with bud rot?

No. Smoking cannabis infected with Botrytis cinerea (bud rot) is highly dangerous. The mould spores can cause severe respiratory infections, allergic reactions, and potentially introduce harmful mycotoxins into your lungs. Any infected plant material should be carefully bagged and discarded.

Can you save buds that have bud rot?

You cannot "cure" or save a bud once it has begun rotting. The visible grey mould is just the fruiting body; the mycelial network has already invaded deep into the vascular tissue of the flower. You must carefully cut away the infected cola, plus at least two inches of seemingly healthy tissue below it, to stop the spread.

Does bud rot spread while drying or in the curing jar?

Yes. Botrytis spores remain active after harvest. If your drying room humidity spikes above 60%, or if buds are placed into curing jars while still too wet, the latent mould spores will germinate and destroy the harvest inside the jar.

Cannabis Research Coverage — The Grower's Connect

Source Study: Yadav SS, Aftab N, Kumar B. Botrytis cinerea infection modulates trichome development and secondary metabolite biosynthesis in Cannabis sativa. Preprint posted February 6, 2026. doi:10.21203/rs.3.rs-8682864/v1 — CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, India. This article is a preprint and has not yet completed peer review.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

Your Smartphone Can Now See What Growers Have Been Guessing At

Your Smartphone Can Now See What Growers Have Been Guessing At
Your Smartphone Can Now See What Growers Have Been Guessing At — AI Harvest Readiness | The Certified
The Grower's Connect
Cultivation Science · Technology

Continuing our cultivation science arc. Last week we asked when the plant is ready — this week, researchers from Ben-Gurion University ask a more ambitious question: can a smartphone and a trained AI model answer that question better than the human eye?

Cultivation Science · AI · Computer Vision · Research 2026

Your Smartphone Can Now See What Growers Have Been Guessing At

A 2026 study from Ben-Gurion University built an AI pipeline that detects, classifies, and correlates trichomes and stigmas with HPLC-measured cannabinoid peaks — using nothing more than a consumer smartphone and a macro lens. Results were consistent across two separate experiments.

The Grower's Connect  ·  2026  ·  12 min read
98.6% trichome classification accuracy — clear, milky, or amber
14,000+ images collected across two greenhouse experiments
2 consistent experiments confirming the stigma colour signal
~55 DAF the green-to-orange stigma crossover point — aligned with cannabinoid peak
Listen to this article Your Smartphone Can Now See What Growers Have Been Guessing At
Audio coming soon — replace this div with your <audio> tag when ready

Every grower has done it. You hold the flower up to a loupe, tilt it toward the light, and try to decide how many trichomes have turned amber. Is it thirty percent? Fifty? The loupe doesn't have a percentage counter. Your eye makes its best guess, your experience fills in the gaps, and you make a call. The same thing happens with stigmas — you eyeball the ratio of orange to green and trust your read.

This is not a criticism of the method. It has worked for decades, for good reason. Trichomes and stigmas really do change colour as the plant matures. The problem is reproducibility. Two experienced growers looking at the same plant can reach different conclusions. The same grower can reach different conclusions on different days. What the field has been missing is an objective, automated system that can extract a precise measurement from an image — and then tell you what that measurement actually means for cannabinoid content.

A study published in Agriculture in February 2026 by researchers at Ben-Gurion University of the Negev, working in collaboration with RCK Science-Based Cannabis Genetics, built exactly that. Their system uses a consumer smartphone fitted with a clip-on macro lens, a multi-stage AI pipeline running Faster R-CNN for trichome detection and YOLOv8 for both trichome classification and stigma segmentation, and a correlation framework that links visual measurements to HPLC-verified cannabinoid data. The study ran two separate experiments across two growing seasons, and the key signals held in both.

Why Two Separate Tools Were Needed

The researchers built a dual-path pipeline because trichomes and stigmas are different problems. Trichomes are small — the tiny glandular structures that produce cannabinoids — and they cluster densely on the flower surface. Stigmas are the larger thread-like structures that receive pollen during fertilisation and visibly shift from green to orange as the plant moves through its flowering period. Each indicator requires its own detection and analysis strategy.

Trichome Path

A fine-tuned Faster R-CNN model detects individual trichomes in high-resolution image patches. A YOLOv8 X-Large classifier then assigns each detected trichome to one of three classes: clear (immature), milky (peak biosynthesis), or amber (post-peak). Classification accuracy across both tasks reached 98.6%.

Stigma Path

A YOLOv8-small segmentation model isolates individual stigmas from the flower image. A pixel-level nearest-neighbour classifier then assigns each pixel within the stigma to either green (immature) or orange (mature). The ratio of orange to green pixels gives a continuous maturity score for each stigma and flower.

Both paths aggregate their outputs at the flower level — so the system doesn't just tell you about one trichome or one stigma, but about the overall profile of the whole flower. Those flower-level statistics were then correlated with HPLC-measured cannabinoid concentrations taken on the same measurement days, giving the team a ground truth to validate against.

The Imaging Setup — What the Smartphone Actually Did

One of the more remarkable aspects of this research is how deliberately low-tech the imaging hardware is. The team used an iPhone 14 Pro and an iPhone 12, each fitted with a Moment Macro Lens M-series clip-on attachment. The iPhone 14 Pro achieved an effective magnification of around thirty times; the iPhone 12 reached twenty times. Both were used with the CameraPixels app, which handled auto-exposure, ISO, and focus settings.

Why This Matters for Growers

The deliberate choice of consumer hardware was not a compromise — it was a design goal. The researchers wanted a system that any cultivator could use without investing in laboratory microscopy or specialised imaging equipment. A clip-on macro lens for a modern smartphone costs a fraction of a professional microscope. If the AI can extract reliable maturity signals from this level of hardware, the barrier to adoption drops dramatically.

Images were captured both inside a working greenhouse — with natural light variation — and in a controlled laboratory environment after harvest, with an adjustable LED lamp. The CameraPixels app's auto-exposure functionality handled the lighting differences, giving the model a diverse and realistic training set rather than one calibrated to ideal lab conditions.

Each high-resolution image was divided into non-overlapping 512 × 512 pixel patches. A pre-processing sharpness filter — based on Canny edge detection — then discarded blurry or out-of-focus patches before passing the remaining regions to the AI models. This filtering step proved critical: one of the key findings from the failure analysis was that image quality, not model capacity, was the primary source of missed detections.

What the AI Actually Detected — and How Well

Trichome detection is the harder of the two problems. The structures are small, they cluster together, and the distinction between a clear and a milky trichome is genuinely subtle. The team tested a wide range of state-of-the-art object detection architectures and found that their two-stage pipeline — Faster R-CNN for detection, then a separate YOLOv8 classifier for the maturity class — outperformed all single-stage alternatives.

Pipeline Performance — Key Metrics

  • Trichome detection with Faster R-CNN (ResNet-50 C4): Precision 0.815, Recall 0.802 — the best balance among all tested architectures at an IoU threshold of 0.5.
  • Trichome classification with YOLOv8 X-Large: overall accuracy 98.6%, with weighted precision and recall both exceeding 0.98 across the three classes (clear, milky, amber).
  • The full two-stage pipeline achieved Precision 0.803 and Recall 0.790, a substantial improvement over the best single-stage model — YOLOv9 — which reached only 0.582 precision and 0.620 recall.
  • Stigma segmentation with YOLOv8-small: AP50 of 52.2%. While moderate in absolute terms, this was sufficient to extract meaningful stigma regions for the colour ratio analysis.
  • Dataset size: over 14,000 images collected across multiple sessions in two experiments, spanning different growing seasons and greenhouse conditions.

The gap between the two-stage pipeline and the single-stage models is worth understanding. The detection stage specialises in finding trichomes — just localising them. The classification stage then focuses entirely on reading the colour of each detected trichome. By separating these two tasks, the system avoids the compounding of errors that happens when a single model tries to do both at once. This is particularly important for the subtle distinction between clear and milky trichomes, which look almost identical to the human eye but carry opposite implications for harvest timing.

"The distinction between milky and clear trichomes is much more difficult than the distinction between green and orange stigmas — and the data shows it. Stigmas outperformed trichomes as harvest predictors, partly because they are larger and easier to image accurately with low-end equipment."

Experiment One — What the Correlations Showed

The first experiment ran across six cannabis cultivars during a spring growing season, imaging flowers at seven time points from day 51 to day 79 after flowering initiation. HPLC measurements were taken on the same days, providing a cannabinoid profile to correlate against the AI-derived visual metrics.

The trichome results were mixed. Milky trichomes showed moderate positive correlations with total cannabinoid levels in some cultivars — supporting the biological expectation that milky trichomes reflect the active biosynthesis phase. Clear trichomes generally showed negative correlations, consistent with immature tissue. But amber trichomes were inconsistent across genotypes: in some cultivars, rising amber ratios accompanied rising cannabinoid levels; in others, they did not.

The Amber Trichome Paradox

Growers are commonly advised to watch for amber trichomes as the harvest signal — yet the data from Experiment 1 showed that amber trichome ratios were the weakest predictor of cannabinoid peak, with RMSE values of 8.68 days compared to 4.54 for orange stigmas. In one cultivar (616), amber trichomes actually showed a negative correlation with Total THC (r = −0.41), meaning rising amber ratios coincided with falling THC. The amber signal is real, but it does not translate cleanly into cannabinoid data across all genotypes.

Stigma colour told a more consistent story. Across all six cultivars, green stigma ratios declined while orange ratios rose over time. The point where those two curves crossed — the visual transition from green-dominant to orange-dominant — closely coincided with the peak in total cannabinoid concentration in most cases. This was especially clear in four of the six cultivars (805-12, 1416-3, 611, and 616), where the crossover nearly aligned with the cannabinoid maximum.

When the team formalised this into a harvest day prediction model — using the first day where the orange stigma ratio exceeded 40% as the threshold — they found it outperformed both milky and amber trichome predictors. Excluding four outlier plants affected by imaging quality issues, the orange stigma predictor achieved an RMSE of 1.83 days for total cannabinoids, compared to 2.57 days for simply predicting the average flowering day.

Experiment Two — Confirming the Signal

The second experiment was conducted during winter 2024–25 using three of the cultivars from Experiment 1, with an improved imaging and annotation protocol designed to address the consistency issues identified in the first round. The results were notably cleaner.

What Experiment Two Confirmed

  • Stigma crossover The green-to-orange stigma transition occurred consistently around 55–60 Days After Flowering across all three cultivars tested, and this inflection point closely coincided with the peak of total cannabinoid levels in each case.
  • Milky trichomes The positive relationship between milky trichome ratios and total cannabinoid concentration became clearer and more consistent in Experiment 2 compared to the mixed results of Experiment 1, supporting the interpretation that milky trichomes reflect the active biosynthesis phase.
  • Amber trichomes Rising amber trichome ratios consistently appeared after the cannabinoid peak — not before or during it. In all three cultivars, amber ratios increased steeply in the late flowering period while THC concentrations declined, reinforcing their role as a post-peak indicator rather than a peak signal.
  • Seasonal consistency The pattern held across two different growing seasons — spring and winter — despite the fact that seasonal differences in light, temperature, and growth rate can significantly influence cannabis development. This consistency strengthens confidence in the underlying biological signal.

The improved sampling protocol in Experiment 2 mattered. Many of the outlier predictions in Experiment 1 were traced back to image quality problems — blurry frames, shallow depth of field, or imaging angle variability that caused the same plant on the same day to yield very different trichome counts depending on how the camera was positioned. When these acquisition variables were better controlled, the biological signal became more consistent.

What the Results Actually Mean for Harvest Decisions

The study is clear that this is a proof-of-concept. Six cultivars in one greenhouse, two smartphone models, and a dataset of thirty plants does not produce a model ready for commercial deployment. The authors say so explicitly. But the directional findings are robust enough to draw practical conclusions.

Reading the Evidence — What Growers Can Take Away

  • Stigma colour is the more reliable visual indicator of peak cannabinoid concentration — more reliable than either milky or amber trichomes — partly because stigmas are larger and easier to image accurately with consumer-grade equipment.
  • The crossover point — where orange stigmas begin to outnumber green — is a more actionable signal than any fixed percentage of trichome colour. In both experiments, this crossover occurred near peak cannabinoid concentration across most cultivars.
  • Amber trichomes are a post-peak signal in most cases. Waiting until trichomes are predominantly amber may mean the plant has already passed its cannabinoid maximum. This directly challenges the most commonly cited version of the amber rule.
  • Milky trichomes are the more relevant trichome signal for cannabinoid peak — but they are harder to classify reliably from smartphone images because the visual distinction between clear and milky is subtle at macro scale.
  • Image quality is the limiting factor, not model capacity. Blurry or out-of-focus frames produce unreliable trichome counts. Consistent focus, steady capture technique, and morning imaging (when greenhouse light is stable) significantly improve output quality.

What Is Still Missing — and What Comes Next

The study's limitations are worth naming clearly. The stigma segmentation model was trained on only 115 images — a small dataset that constrains how well it generalises to different cultivars, lighting conditions, and camera hardware. The correlation experiments covered six cultivars in Experiment 1 and three in Experiment 2, which is not enough to build genotype-independent maturity prediction models.

The trichome-to-cannabinoid correlations were also inconsistent across genotypes in Experiment 1, which the authors attribute to both biological variability and sampling limitations. Some cultivars showed strong patterns; others showed weaker or inverted ones. This genotype-dependency is a known challenge in cannabis phenotyping and is not specific to this study — it was also a finding in last week's Tran et al. paper on stigma colour staging across 25 genotypes.

The Consistent Finding Across Both Papers

Two independent research groups, different methodologies, different scales of experiment — and both converged on the same conclusion: the green-to-orange stigma transition is a more reliable visual indicator of peak cannabinoid concentration than trichome colour alone. Last week's Tran et al. study established this across 25 genotypes using manual staging. This week's Lorberboym et al. study automated the measurement and confirmed the same signal across two growing seasons using AI. The convergence is significant.

The authors identify the path forward: larger datasets across more cultivars and environments, better image acquisition protocols with automated quality filtering built into the capture step, and direct integration testing in live greenhouse workflows. They also note the possibility of combining the visual pipeline with additional inputs — days after flowering, temperature data, cultivar-specific calibration — to build a multi-feature model once sufficient training data exists.

The long-term vision is a field-ready tool that any cultivator can use on a smartphone: point it at a flower, capture a sharp macro image, and receive an AI-derived maturity score alongside a harvest recommendation window. That tool doesn't exist yet at commercial scale. But this paper shows it is not a distant possibility. The biology is consistent. The AI can read it. The question now is how many more flowers, cultivars, and seasons of data it takes to make the system robust enough to trust.

Cannabis Research Coverage — The Grower's Connect

Source Study: Lorberboym E, Lazare S, Golshmid P, Shani G. Estimating Cannabis Flower Maturity in Greenhouse Conditions Using Computer Vision. Agriculture 2026, 16, 460. doi:10.3390/agriculture16040460 — Faculty of Computer and Information Science, Ben-Gurion University of the Negev, Beer-Sheva, Israel; RCK Science-Based Cannabis Genetics, Kibbutz Ruhama, Israel. Published 16 February 2026. Funded in part by the Israeli Innovation Authority, grant 8114581.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

The Amber Rule

When to Harvest — What Science Says About the Amber Rule | The Certified
The Grower's Connect
Cultivation Science · Harvest

A new direction in our weekly research coverage. We've been tracking the cannabis science arc from the lab to the clinic — this week we turn to the grow room. A 2025 study from Agriculture Victoria Research asks the question every cultivator already thinks they know the answer to: do amber stigmas actually signal peak cannabinoids?

Cultivation Science · Harvest Timing · Research 2025

The Amber Rule — What Science Actually Found When It Tested the Grower's Most Trusted Signal

Growers have watched stigma colour for decades to judge harvest timing. A 2025 study from Agriculture Victoria Research tracked 25 diverse cannabis genotypes, measured 14 cannabinoids at each colour stage, and tested whether the rule holds — and when it doesn't.

The Grower's Connect  ·  2025  ·  11 min read
22/25 genotypes peaked at stage 3 or 4 — mostly to fully amber
14 cannabinoids tracked per sample across all genotypes
87 mg/g highest total cannabinoid concentration recorded — Genotype 13
119 days of harvest data collected after flowering initiation
Listen to this article The Amber Rule — What Science Actually Found When It Tested the Grower's Most Trusted Signal
Audio coming soon — replace this div with your <audio> tag when ready

The amber stigma rule is one of the oldest and most widely shared pieces of practical knowledge in cannabis cultivation. When the fine thread-like structures on the female flower — the stigmas — transition from white to amber, the plant is telling you something. Most experienced growers treat a mostly amber reading as the harvest signal. Most new growers are taught to do the same.

The problem is that this rule of thumb has circulated largely without scientific validation. Growers developed it through observation, passed it down through practice, and refined it through seasons of trial and error. Whether stigma colour is actually correlated with cannabinoid concentration — and precisely when peak concentration occurs relative to the colour transition — had not been rigorously tested across a meaningful range of genotypes.

Posted on by

Cannabis in the Oncology Ward

Cannabis in the Oncology Ward
Cannabis in Cancer Care — What the Evidence Actually Shows | The Certified
The Grower's Connect
Research · Cannabis Science

Part of our ongoing coverage of peer-reviewed cannabis research. Previous entries: CBD and THC Together in Ovarian Cancer Cells, and What the Science Actually Says About Cannabis and Cancer. This week: a comprehensive clinical review from Israel's Soroka Medical Center — cannabis as a tool for the oncology ward.

Cannabis Science · Oncology · Clinical Review 2024

Cannabis in the Oncology Ward — What Patients Need, What Clinicians Know, and Where the Gap Lies

A 2024 narrative review from Soroka Medical Center synthesises the evidence on cannabis across five domains of oncology care — pain, nausea, appetite, sleep, and anti-tumour activity. The picture is more nuanced than either advocates or sceptics tend to acknowledge.

The Grower's Connect  ·  2024  ·  13 min read
70% of cancer patients use cannabis products during treatment
83% one-year survival in glioblastoma patients on cannabinoid + chemo
36% of opioid-using cancer patients ceased opioids after 6 months on cannabis
500+ chemical compounds identified in Cannabis sativa
Listen to this article Cannabis in the Oncology Ward — What Patients Need, What Clinicians Know, and Where the Gap Lies
Audio coming soon — replace this div with your <audio> tag when ready

Somewhere between 60 and 70 percent of cancer patients are already using cannabis products during their treatment. They are doing so largely without guidance, because the oncologists treating them — through no fault of their own — often lack the evidence base required to offer meaningful recommendations. Cannabis research has been constrained for decades by regulatory frameworks that classified it alongside hard drugs, and the catch-up has been uneven. The laboratory science is now substantial. The clinical trial data is thinner and more complicated.

A 2024 narrative review published in Cancers by researchers at Soroka Medical Center and Ben Gurion University of the Negev sets out to bridge that gap. The paper is explicitly addressed to both clinicians and patients — a relatively unusual framing in a peer-reviewed oncology journal. It covers cannabis history, pharmacology, methods of consumption, symptom management across five domains, anti-tumour activity, and side effects. It is comprehensive in scope and candid about where the evidence runs out.

This is the framework through which we will examine it — not as a summary, but as an honest accounting of what the research does and does not support.

The Knowledge Problem — Why Oncologists Can't Answer Their Patients' Questions

The review opens with an observation that will resonate with anyone who has navigated cancer care: patients seeking to integrate cannabis into their treatment encounter frustration when their oncologists lack adequate information to provide guidance. This is not a failure of individual physicians. It is a structural consequence of decades of suppressed research.

Cannabis was removed from the US pharmacopeia in 1941, following mounting legal restrictions that classified it alongside other controlled substances. Research into its medicinal applications slowed significantly for more than half a century. By the time the endocannabinoid system was properly characterised — cannabinoid receptor 1 was identified in the early 1990s — the scientific and clinical infrastructure needed to study cannabis properly was still decades behind where it would have been without the interruption.

"As many as 70% of oncologists report having discussions with their patients about cannabis. But they also acknowledge lacking the comprehensive information needed to make robust recommendations."

The result is a knowledge asymmetry that operates in both directions. Patients who have heard promising anecdotal accounts of cannabis and cancer arrive with questions that their physicians cannot confidently answer. Physicians who are aware of the preclinical evidence but lack access to clinical trial data are uncomfortable offering guidance that might be wrong in either direction — either overstating benefit or unnecessarily discouraging something that might help.

The Endocannabinoid System — The Biological Context That Makes This All Possible

To understand why cannabis interacts with cancer in the ways it appears to, you need to understand the endocannabinoid system. This is not optional background — it is the mechanism through which all the therapeutic effects described in this review operate.

Cannabis sativa contains over 500 chemical compounds, of which at least 100 are phytocannabinoids. The most studied are delta-9-tetrahydrocannabinol (THC), which produces psychoactive effects, and cannabidiol (CBD), which does not. The plant also contains terpenes and flavonoids that contribute to its biological activity through what researchers call the entourage effect — the enhanced benefit of compounds working together rather than in isolation.

Components of the Endocannabinoid System

  • CB1 Receptors Predominantly found in the central nervous system. Regulate mood, appetite, pain perception, nausea response, and memory. Highly expressed in brain regions governing nociceptive processing — making them a key target for pain and nausea management.
  • CB2 Receptors Primarily expressed in immune cells. Modulate inflammatory responses and are expressed on tumour cells, where their activation can trigger anti-cancer signalling cascades including apoptosis.
  • Endogenous Ligands Anandamide (AEA) and 2-arachidonoylglycerol (2-AG) are the body's own cannabinoids. Anandamide has shown anti-proliferative effects in prostate and other cancers. Both are produced on demand and degraded by dedicated enzymes (FAAH for AEA; MAGL for 2-AG).
  • Non-Canonical Receptors Cannabinoids also interact with GPR55 and transient receptor potential (TRP) channels — non-CB1/CB2 receptors that mediate additional effects including some of the anti-tumour activity observed in preclinical models.

CB1 and CB2 receptors are expressed not just on neurons and immune cells but on tumour cells themselves. CB1 and CB2 agonists selectively inhibit production of VEGF-A — a potent driver of angiogenesis — in activated immune cells, which has direct relevance to tumour blood vessel formation. This is the biological scaffolding upon which the anti-tumour evidence rests.

How People Actually Use Cannabis — And Why It Matters Clinically

Before turning to therapeutic effects, the review addresses something often skipped in academic treatments of this subject: the practical pharmacology of different consumption methods. This matters for oncology patients because onset time, bioavailability, and dose control vary substantially depending on how cannabis is consumed — and getting the dose wrong has real consequences in patients who are already immunocompromised and managing complex medication regimens.

Inhalation — Smoked or Vaporised

Rapid onset — clinically useful when nausea is the dominant symptom. Allows for easier dose titration, reducing the risk of overconsumption. Vaporisers can concentrate THC to 90%, posing cardiovascular risks in susceptible patients. Common side effects include throat irritation and coughing.

Oral and Sublingual

Rising in popularity with edibles, tinctures, and dissolvable strips. Poor and unpredictable pharmacokinetics — bioavailability of only 6–25%, with absorption delayed or altered by stomach contents. High risk of overconsumption as patients wait for delayed onset. Sublingual administration (including Sativex) may offer faster uptake.

Topical Application

Patches, salves, lotions, and oils applied to the skin. Sustained drug release with minimal systemic absorption, limiting psychoactive side effects. Best suited to localised symptoms — arthritis, dermatological conditions. Popular with older patients and first-time users seeking symptom relief without intoxication.

A Note on Drug Interactions

Cannabinoids are both inhibitors and inducers of CYP enzymes — the liver proteins responsible for metabolising the majority of pharmaceutical drugs. One study found medicinal cannabis did not significantly affect pharmacokinetics of irinotecan or docetaxel. But CBD and CBN are potent inhibitors of CYP1A1, and interactions with other chemotherapy agents require caution and monitoring.

Appetite and Weight — What the Numbers Actually Show

Appetite loss and cancer-related cachexia — the progressive wasting syndrome seen in advanced cancer — are among the most distressing consequences of both the disease and its treatment. Cannabis has long been understood to stimulate appetite, and the review provides specific data on how this effect compares to standard pharmacological options.

Studies indicate that cannabis can increase caloric intake by approximately 40%, with the effect distributed across the day rather than concentrated at mealtimes. Interestingly, the caloric increase is driven primarily by snacks — particularly sweet solid foods — which has implications for nutritional counselling. The effect on actual weight gain is more variable.

Cannabis vs Megestrol Acetate — Appetite Improvement Trial

  • 469 advanced cancer patients enrolled. Three arms: megestrol acetate (800 mg), dronabinol (2.5 mg), or both.
  • Megestrol acetate produced the highest rate of appetite improvement — 75% of patients experienced increased appetite.
  • The combination of both compounds produced appetite improvement in 66% of patients.
  • Dronabinol alone produced appetite improvement in 49% of patients.
  • Weight gain exceeding 10%: 11% of patients on megestrol vs 3% on dronabinol.
  • Nabilone (another cannabinoid medicine) significantly increased caloric intake by 342 kcal compared to placebo in a separate lung cancer trial, while also improving quality of life measures.

The data here is nuanced. On raw appetite improvement numbers, the established pharmaceutical megestrol outperforms dronabinol. But the trials were not designed to test whole-plant cannabis preparations, which differ from isolated synthetic cannabinoids in ways the research is only beginning to characterise. Higher CBD strains appear to produce less appetite stimulation than high-THC preparations — a ratio consideration with direct relevance for product selection in clinical settings.

Pain Management — The Case That Is Most Developed

Pain is the symptom domain in which the cannabis evidence is deepest, and the Soroka review covers it with appropriate complexity. Cancer pain is not a single entity. It arises from bone metastasis, spinal cord compression, chemotherapy-induced peripheral neuropathy, pathological fractures, and nerve compression — each with somewhat different pharmacological requirements.

The current standard involves opioid analgesics, which carry risks of dependence and dose-escalation that are particularly problematic in patients already managing complex treatment regimens. The review describes cannabinoids as a potential alternative or adjunctive therapy — one that engages different pain mechanisms entirely, through CB1 and CB2 receptors rather than opioid receptors, meaning their analgesic effects are not blocked by opioid antagonists.

Key Clinical Finding

A study of 2,000 cancer patients using cannabis found that among the 344 individuals using opiates at baseline, 36% had ceased opiate use entirely and 10% had reduced their dosage within six months of beginning cannabis. Adding vaporised cannabis to existing morphine or oxycodone regimens reduced pain by 27% without altering plasma opioid levels in a separate clinical pharmacology study.

The chemotherapy-induced peripheral neuropathy data is particularly interesting. A retrospective analysis of 513 patients treated with oxaliplatin found that cannabis significantly reduced the rate of neuropathy — 15.3% in cannabis users versus 27.9% in controls. The protective effect was more pronounced in patients who began cannabis before starting oxaliplatin treatment (75% protection) versus those who started cannabis afterward (46%). This temporal finding — that early introduction matters — has direct implications for when cannabis should be discussed with patients, not just whether.

The only published controlled trial on cannabis for chemotherapy-induced peripheral neuropathy — involving 16 patients randomised to nabiximols or placebo — found no statistically significant difference between groups on average pain scores. However, responder analysis revealed clinically significant pain reduction in a subset of patients, with a mean reduction of 2.6 points on a 0–10 scale and a number needed to treat of five. The trial was small. The question it raises is not closed.

Nausea and Vomiting — The Established Indication

If there is one domain in which cannabis has the clearest established evidence for cancer patients, it is chemotherapy-induced nausea and vomiting. Multiple national academies of science, systematic reviews, and a Cochrane analysis have concluded that oral cannabinoids are effective antiemetics in adults undergoing chemotherapy. The biological mechanism runs through CB1 receptors on dopaminergic and noradrenergic neurons in brain regions governing the emetic response.

The review highlights a phase II crossover trial that is worth examining in detail. Eighty-one cancer patients receiving emetogenic intravenous chemotherapy, with persistent nausea and vomiting despite standard antiemetics, were randomised to THC:CBD capsules (2.5 mg each, three times daily) or placebo across two chemotherapy cycles, with patients choosing their preferred treatment for a third cycle.

THC:CBD Crossover Trial — Refractory Chemotherapy Nausea

  • Complete response (no nausea or vomiting) improved from 14% on placebo to 25% on THC:CBD combination.
  • Relative risk of complete response: 1.77 (95% CI: 1.12–2.79; p = 0.041).
  • Moderate-to-severe adverse events were more frequent with THC:CBD — 31% versus 7% on placebo.
  • Despite the higher adverse event rate, 83% of participants preferred the cannabinoid treatment over placebo.
  • A smaller earlier trial using oral mucosal cannabis extract found a complete response rate of 71.4% in the cannabis group versus 22.2% in the placebo group.

The 83% patient preference figure deserves emphasis. In a population already dealing with significant adverse effects of cancer treatment, 83% of patients preferred a therapy that produced more side effects than placebo — because those side effects were less burdensome than uncontrolled nausea. This is a patient-centred outcome measure that purely statistical analyses can obscure.

The review notes that the American Society of Clinical Oncology's expert panel remains cautious, citing insufficient data to formally recommend medical cannabis for nausea prevention. This is a legitimate scientific conservatism — but it sits in some tension with the reality that most cancer patients are already making their own decisions without formal guidance.

Sleep — An Underexplored but Clinically Significant Domain

Sleep disturbance affects up to 19% of the general population and is substantially more prevalent among cancer patients. It is also among the least well-studied applications of cannabis in oncology. The review's treatment of this domain is appropriately cautious about what the evidence can and cannot support.

Short-term, high-dose CBD may assist in reducing sleep onset latency and prolonging sleep duration — possibly through CBD's anxiolytic properties rather than through direct sedation. Nabiximols studies involving cancer patients in pain have reported subjective improvements in sleep quality, though the review notes these may reflect reduced pain rather than changes to sleep biology itself. This distinction matters for product selection.

The Tolerance Problem

Frequent use of high-THC cannabis products can lead to tolerance, driving patients to self-titrate upward over time in pursuit of the same sleep benefit. Stopping cannabis after prolonged use can worsen insomnia as a withdrawal effect — creating a dependency dynamic that is particularly problematic in a patient population already managing complex medications. The longer half-life of oral or sublingual formulations may make them preferable for sleep duration, but evidence-based dosing guidance for this application is currently lacking.

Anti-Tumour Effects — The Evidence Hierarchy

This is the domain that attracts the most attention and generates the most confusion — both in the popular press and in clinical conversations. The review addresses it systematically, distinguishing between preclinical findings, early clinical results, and the significant gap between them.

The preclinical case is substantial. Cannabinoids interfere with cancer cell biology through multiple mechanisms: they induce apoptosis (programmed cell death) directly, block tumour angiogenesis by inhibiting VEGF-A production, suppress metastasis, trigger autophagy, and inhibit cell proliferation. These effects have been demonstrated across lung, breast, prostate, glioblastoma, and ovarian cancer models, among others. The endocannabinoid anandamide inhibits proliferation in prostate cancer cell lines by downregulating epidermal growth factor receptor expression. THC and the synthetic cannabinoid JWH-133 reduce tumour growth, metastases, and angiogenesis in breast cancer mouse models through Akt pathway inhibition.

Apoptosis Induction

Cannabinoids trigger programmed cancer cell death through caspase activation, mitochondrial cytochrome c release, and modulation of Bcl-2 family proteins. This mechanism has been demonstrated across lung, breast, glioblastoma, and prostate cancer models.

Anti-Angiogenesis

CB1 and CB2 agonists selectively inhibit VEGF-A production from activated immune cells — blocking the formation of new blood vessels that feed tumour growth. Reduced angiogenesis and endothelial permeability have been observed in multiple cancer models.

Anti-Proliferation

Cannabinoids slow cancer cell division through interference with cell cycle checkpoints and PI3K-Akt, MAPK, and ERK signalling pathways. CBD constitutes up to 40% of cannabis extracts and exerts anti-proliferative effects without psychoactivity.

Autophagy Induction

Cannabinoids induce synthesis of ceramide, which activates an endoplasmic reticulum stress-related signalling pathway leading to cell death through autophagy. This is a distinct mechanism from classical apoptosis, relevant in cancers that have developed resistance to apoptotic pathways.

The most clinically advanced anti-tumour evidence involves glioblastoma multiforme — the most aggressive form of brain cancer. A pilot trial involving intracranial THC administration in recurrent glioblastoma patients found tumour proliferation reduction in two of nine patients. The subsequent nabiximols plus temozolomide trial produced the result that now anchors the entire clinical anti-tumour discussion.

Glioblastoma — Nabiximols + Temozolomide Trial

  • Glioblastoma patients receiving nabiximols spray combined with temozolomide chemotherapy.
  • One-year survival rate in the nabiximols group: 83%.
  • One-year survival rate in the placebo group: 44%.
  • The nabiximols treatment was well-tolerated with no significant additional adverse events beyond the chemotherapy baseline.
  • These results have not yet been replicated in a larger Phase III trial — a critical caveat that does not reduce the significance of the signal.

A finding with very different implications also appears in the review — one that deserves equal attention. A study of 68 metastatic cancer patients beginning immunotherapy found that cannabis users demonstrated a median time to tumour progression of only 3.4 months, compared to 13.1 months in non-users. Median survival was 6.4 months in cannabis users versus 28.5 months in non-users. The anti-inflammatory properties of cannabis may interfere with the mechanism by which immunotherapy activates the immune system against tumours — a critical interaction that has not yet been adequately characterised in randomised trials.

The Immunotherapy Caution

This is not a finding to dismiss or minimise. Cannabis users in immunotherapy studies experienced lower lymphocyte counts and fewer immune-related adverse events — consistent with cannabis having an immunosuppressive effect that could directly undermine the mechanism of checkpoint inhibitor therapy. Until this interaction is better understood in randomised controlled trials, patients receiving immunotherapy should discuss cannabis use explicitly with their oncologist. The same anti-inflammatory property that makes cannabis useful for symptom management may, in this specific treatment context, reduce efficacy.

Side Effects — An Honest Accounting

The review does not advocate uncritically. It presents the adverse effect profile of cannabis with the same rigour applied to the therapeutic evidence. This balance is one of the paper's genuine strengths.

Acute psychoactive effects of THC include euphoria, anxiety, sensory distortions, altered time perception, and paranoia. At higher doses — particularly from concentrated vaporised products — arrhythmia and myocardial infarction risk increase in susceptible individuals. The most common adverse effects of synthetic cannabinoids in a review of over 3,600 toxicity reports were tachycardia (30%), agitation (13.5%), drowsiness (12.3%), nausea and vomiting (8.2%), and hallucinations (7.6%). Deaths and severe outcomes were rare (0.2% and 0.1–0.09% respectively).

For chronic use, the concerns are different: tolerance development, withdrawal effects including severe depressive episodes, increased systolic hypertension risk, ischaemic stroke risk, and ventricular arrhythmia risk. Cannabis also reduces immune response to some infections — a consideration that cannot be ignored in immunocompromised cancer patients.

Non-psychoactive CBD presents a substantially better risk-benefit profile. Its absence of psychoactivity eliminates several of the acute concerns, and it constitutes up to 40% of whole-plant cannabis extracts. The challenge is that the anti-tumour and symptom management literature does not always clearly distinguish between CBD-dominant, THC-dominant, and balanced preparations — making clinical translation of specific findings more complicated than headlines suggest.

What the Review Asks of Researchers, Clinicians, and Regulators

The Soroka review is ultimately a call to action addressed to three audiences simultaneously. For researchers, it identifies the specific gaps: adequately powered randomised controlled trials with standardised preparations, clear patient stratification, and outcomes that capture quality of life alongside disease progression. For clinicians, it offers a framework for evidence-based conversations with patients who are already using cannabis and need guidance rather than dismissal. For regulators, it documents that the knowledge gap is not a scientific problem but a structural one — created by decades of regulatory restriction and maintainable only by continued restriction.

The paper's most useful contribution may be its honest acknowledgement of what the evidence does and does not support. Cannabis is not a cancer cure. It is a complex plant producing biologically active compounds that interact with fundamental aspects of cancer biology in ways that are scientifically credible, reproducible across multiple research groups, and — in the glioblastoma case — clinically promising. It is also a compound with genuine risks, genuine drug interactions, and at least one documented context — immunotherapy — where its use may be harmful.

That complexity is precisely what patients deserve to hear, and exactly what this review tries to provide.

Cannabis Research Coverage — The Grower's Connect

Source Study: Shalata W, Abu Saleh O, Tourkey L, Shalata S, Neime AE, Abu Juma'a A, Soklakova A, Tourkey L, Jama AA, Yakobson A. The Efficacy of Cannabis in Oncology Patient Care and Its Anti-Tumor Effects. Cancers 2024, 16, 2909. doi:10.3390/cancers16162909 — The Legacy Heritage Center and Dr. Larry Norton Institute, Soroka Medical Center, and Ben Gurion University of the Negev, Beer Sheva, Israel. Published 21 August 2024.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

CBD, Prostate Cancer, and the Cell That Refuses to Stop

CBD, Prostate Cancer, and the Cell That Refuses to Stop
CBD, Prostate Cancer, and the Cell That Refuses to Stop — What a 2023 Study Reveals | The Certified
The Grower's Connect
Research · Cannabis Science

Part of our ongoing coverage of peer-reviewed cannabis research. Previously: A Combination No One Was Looking For — CBD and THC Together in Ovarian Cancer Cells. This week: a focused look at what CBD does to prostate cancer cells — and to the molecular machinery driving them.

Cannabis Science · Prostate Cancer · Research 2023

CBD, Prostate Cancer, and the Cell That Refuses to Stop

A peer-reviewed study from University College Dublin tested cannabidiol against three prostate cancer cell lines — including the most aggressive, treatment-resistant type. It stopped cancer cells from proliferating, reduced their ability to invade surrounding tissue, and did so through a molecular pathway that doesn't depend on the cannabinoid receptors most people assume are involved.

The Grower's Connect  ·  2025  ·  11 min read
3 prostate cancer cell lines tested — hormone-sensitive and resistant
~30% reduction in PC-3 cell invasiveness at noncytotoxic CBD doses
2× increase in E-cadherin expression — a marker of non-invasive cell behaviour
4 cell cycle proteins downregulated: CDK1, CDK2, CDK4, cyclin D3
Listen to this article CBD, Prostate Cancer, and the Cell That Refuses to Stop
Audio coming soon — replace this div with your <audio> tag when ready

Prostate cancer is the fifth leading cause of cancer death in men. When it is caught early and localised, the five-year survival rate is close to 100%. But when it progresses to metastatic disease — when it spreads beyond the prostate — that survival rate drops to 30%. And when it becomes castration-resistant, developing the ability to grow independently of the androgens that standard therapy targets, it is currently considered incurable.

This is the clinical reality that a team of researchers at University College Dublin set out to engage with when they published a study in the Journal of Natural Products in 2023, asking a focused question: what does cannabidiol do to prostate cancer cells, how exactly does it do it, and does the effect extend to the cancer's ability to invade surrounding tissue?

The answers they found are detailed, mechanistically grounded, and connect directly to what we have been building in this series — particularly to last week's ovarian cancer study, which identified the PI3K/AKT/mTOR signalling axis as a key target of cannabinoid action. That same signalling axis appears here, through a different molecular entry point, in a different cancer, reinforcing a pattern that the broader research literature is increasingly difficult to dismiss.

The Problem With Prostate Cancer Treatment

Understanding what this study found requires understanding what makes prostate cancer so difficult to treat once it escapes early-stage management. Most prostate cancers are initially driven by androgens — the male hormones, primarily testosterone. Androgen deprivation therapy removes that fuel source and works well initially. The problem is that over time, tumour cells adapt. They develop the ability to maintain androgen receptor signalling without the androgens themselves, or they find entirely androgen-independent growth pathways. At that point, the standard treatment no longer controls the disease.

The two key features of advanced prostate cancer that any new therapeutic approach needs to address are proliferation — the uncontrolled division of cancer cells that drives tumour growth — and invasion — the ability of cancer cells to break out of the prostate, penetrate surrounding tissue, and establish new tumour foci elsewhere in the body. Metastasis is the cause of approximately 90% of all cancer deaths. Any compound that can meaningfully inhibit both of these behaviours in prostate cancer cells is scientifically worth taking seriously.

"When prostate cancer becomes metastatic, the five-year survival rate drops to 30%. When it becomes castration-resistant, it is currently considered incurable. The need for new therapeutic strategies is not academic — it is urgent."

How the Study Was Designed

The researchers used three established prostate cancer cell lines that represent different stages and hormone sensitivities of the disease. DU145 and PC-3 are both androgen-insensitive — they do not depend on androgens to grow, making them models of advanced, treatment-resistant prostate cancer. LNCaP is androgen-sensitive, modelling earlier-stage hormone-driven disease.

CBD was supplied by GreenLight Pharmaceuticals at a purity above 99.7%, verified by convergence chromatography. This level of purity matters for mechanistic research — it ensures that any effect observed is attributable to CBD specifically, not to other constituents in a cannabis extract.

The study also included two noncancerous prostate epithelial cell lines — PWR-1E and RWPE-1 — to determine whether CBD's effects are specific to cancer cells or whether they also affect healthy tissue. This is the same design principle we highlighted last week in the ovarian cancer study, and it is the correct way to assess therapeutic potential versus non-selective toxicity.

What CBD Did to Cancer Cell Viability

Under serum deprivation conditions — which remove the buffering effect of proteins in growth media — CBD reduced the viability of all three cancer cell lines in a dose-dependent manner. The IC50 values at 72 hours were 1.5 micromolar for DU145, 2.9 micromolar for PC-3, and 2.6 micromolar for LNCaP cells.

The study also tested CBD in the presence of serum, which reflects more realistic growth conditions and is known to reduce cannabinoid efficacy because serum proteins bind to CBD and reduce its free concentration in the medium. Under serum conditions, the IC50 values rose to 12.3 micromolar for DU145, 10.5 micromolar for PC-3, and 18.0 micromolar for LNCaP. The androgen-independent lines — DU145 and PC-3 — remained more sensitive to CBD than the androgen-dependent LNCaP line under these conditions, which is a relevant finding given that androgen-independent disease represents the harder therapeutic challenge.

Why Serum Conditions Matter

In vitro studies conducted without serum often produce artificially low IC50 values that do not translate to realistic therapeutic concentrations. The fact that this study tested CBD under both conditions, and reported both sets of results honestly, is a mark of methodological rigour. The serum-present IC50 values of 10 to 18 micromolar are the figures more likely to approximate what would be needed in a clinical context — though in vivo pharmacokinetics would also change the picture significantly.

Beyond simple viability, the researchers used multiple complementary methods to understand what was actually happening to the cells. Flow cytometry confirmed that CBD significantly reduced total cell counts in both DU145 and PC-3 lines. A clonogenic assay — which tests a cell's ability to form a colony after treatment, reflecting long-term survival and proliferative potential — showed that CBD pretreatment reduced PC-3 colony formation by approximately 25% after seven days of recovery without further treatment. This means CBD's inhibitory effect persists beyond the treatment period, which is relevant for any therapeutic application.

High-content fluorescence microscopy revealed that at doses of 5 and 10 micromolar — in the presence of serum — CBD significantly reduced cell confluency in DU145 and PC-3 cells, confirming inhibition of proliferation. Crucially, CBD did not significantly increase markers of cell death at these concentrations. The primary effect in cancer cells grown with serum was the slowing of proliferation, not the induction of apoptosis. This is an important distinction: CBD appears to work predominantly as a cytostatic agent in prostate cancer cells under physiologically relevant conditions rather than as an acute cell killer.

The Receptor Mystery — What CBD Is Not Using

One of the most scientifically interesting findings in this study is what CBD is not doing. The conventional understanding of cannabinoid pharmacology centres on the CB1 and CB2 receptors — the two primary cannabinoid receptors that THC binds to directly. Many of CBD's effects in other contexts have been attributed to these receptors, to the TRPV1 ion channel, and to GPR55, a receptor that some researchers consider a third cannabinoid receptor.

To determine which receptors were mediating CBD's effects in prostate cancer cells, the researchers pretreated cells with selective blockers of each of these targets before applying CBD. If blocking a receptor reduced CBD's effect, that receptor would be implicated in the mechanism. None of them were.

Receptor Blockade Experiment — What Was Tested and What It Showed

  • CB1 antagonist (SR141716): no significant difference in CBD's effect on cell viability in DU145 or PC-3 cells.
  • CB2 antagonist (SR144528): no significant difference in CBD's effect on cell viability in either cell line.
  • TRPV1 channel blocker (capsazepine): no significant difference in CBD's effect on cell viability in either cell line.
  • GPR55 agonist (lysophosphatidylinositol): no significant difference in CBD's effect on cell viability in either cell line.
  • Conclusion: CBD reduces prostate cancer cell viability independently of all four of these commonly cited cannabinoid targets.

This finding does not mean CBD has no receptor targets — it means the targets that mediate its effects in prostate cancer cells remain to be identified. The researchers suggest CBD may be acting through PPARgamma, mitochondrial proteins such as VDAC1, ion channels including TRPM8 and TRPA1, serotonin receptors, or steroid receptors. This is consistent with CBD's known pharmacological promiscuity — it interacts with a wide range of molecular targets across different cell types, and the relevant target appears to vary by tissue and cancer type.

For the purposes of understanding what this means practically: CBD's anticancer effects in prostate cells appear to be receptor-independent, at least with respect to the classical cannabinoid receptor system. This matters because it suggests the mechanism is not simply a consequence of endocannabinoid system modulation but reflects a more fundamental disruption of cancer cell biology.

The Cell Cycle — Where the Action Is

Having established that CBD inhibits prostate cancer cell proliferation, the researchers investigated why — specifically, what happens to the proteins that drive the cell cycle.

The cell cycle is the sequence of events that a cell goes through to duplicate itself and divide. It has multiple checkpoints — the G1/S transition and the G2/M transition are the two most important — and each checkpoint is controlled by a set of proteins called cyclins and cyclin-dependent kinases. Cancer cells typically have dysregulated cell cycle control, which allows them to divide far more rapidly than normal cells. Compounds that restore that control by reducing the levels or activity of these proteins can slow or stop cancer cell proliferation.

Cell Cycle Proteins Altered by CBD Treatment

  • CDK2 Significantly reduced in DU145 cells (p equals 0.049) and in PC-3 cells (p equals 0.04). CDK2 drives progression through the G1/S checkpoint, the first major cell cycle decision point.
  • CDK4 Significantly reduced in DU145 cells (p equals 0.04). CDK4 also promotes G1/S transition. Its downregulation, combined with CDK2 reduction, suggests CBD blocks cell cycle progression before DNA replication begins.
  • Cyclin D3 Significantly reduced in PC-3 cells (p equals 0.0002). Cyclin D3 partners with CDK4 to drive the G1/S transition. Its reduction in PC-3 cells is the most statistically powerful result in the cell cycle dataset.
  • CDK1 Significantly reduced in both DU145 (p less than 0.0001) and PC-3 (p equals 0.02) cells. CDK1 controls the G2/M checkpoint — the second major decision point before cell division. The authors note this is, to their knowledge, the first evidence that CBD reduces CDK1 expression in cancer. The effect in DU145 cells was particularly strong.

Taken together, CBD appears to block cell cycle progression at both major checkpoints simultaneously — the G1/S transition, where the cell commits to DNA replication, and the G2/M transition, where it commits to division. This dual-checkpoint disruption is consistent with the potent anti-proliferative effect observed in the viability and confluency assays, and it adds mechanistic specificity to what the broader literature had previously described in more general terms.

The AKT story adds another dimension. AKT is a protein kinase — a molecular switch — whose phosphorylated, active form promotes cancer cell proliferation, survival, and invasiveness. AKT hyperphosphorylation is a common feature of prostate cancer, observed in approximately 50% of cases. Last week's ovarian cancer study showed that the CBD:THC combination markedly reduced phospho-AKT levels as part of the PI3K/AKT/mTOR cascade. Here, CBD alone significantly reduced AKT phosphorylation by approximately 40% in DU145 cells. This connects prostate cancer to the same signalling axis we documented in ovarian cancer, glioblastoma, and multiple other cancer types across this series — suggesting AKT phosphorylation inhibition may be one of the more consistent targets of CBD's anticancer action.

Stopping the Spread — The Invasion Finding

The anti-invasion data may be the most clinically significant finding in the study, because invasion is the behaviour that ultimately kills patients.

Using a Transwell invasion assay with extracellular matrix — a standard method for measuring how readily cells can push through a barrier that mimics the tissue they would need to penetrate to spread — the researchers found that a noncytotoxic dose of CBD reduced PC-3 cell invasiveness by approximately 30%. This is important phrasing: noncytotoxic means the dose was not high enough to kill cells. The reduction in invasiveness occurred at a concentration at which the cells were still alive and growing — it was a change in cell behaviour, not a consequence of cell death.

PC-3 Invasion Reduced ~30%

PC-3 is the most aggressive of the three cell lines tested — androgen-independent and highly metastatic. A 30% reduction in invasiveness at a noncytotoxic dose suggests CBD can change how these cells behave without needing to kill them, which is relevant for sustained therapeutic use.

E-Cadherin More Than Doubled

E-cadherin is an adhesion protein that holds epithelial cells together. Cancer cells that lose E-cadherin become more mobile and invasive — a process called epithelial-mesenchymal transition. CBD induced a greater than twofold increase in E-cadherin expression in PC-3 cells, suggesting it is pushing these cells back toward a less invasive phenotype.

Matrix Metalloproteinases Unchanged

In breast cancer, CBD's anti-invasive effects were accompanied by reduced secretion of matrix metalloproteinases — enzymes that digest the extracellular matrix and clear a path for invading cells. Here, MMP-1, MMP-3, and MMP-9 were unchanged, indicating the mechanism of anti-invasion in prostate cancer cells is E-cadherin restoration rather than MMP suppression.

DU145 Invasion Unchanged

CBD did not significantly reduce DU145 cell invasiveness. This cell-line specificity is scientifically honest and practically informative — not all prostate cancer subtypes respond to CBD in the same way, and understanding which cellular contexts are most responsive is essential for any future therapeutic development.

The E-cadherin finding deserves emphasis. The loss of E-cadherin is one of the hallmarks of epithelial-mesenchymal transition — the process by which cancer cells acquire the capacity to invade and metastasise. CBD is not merely slowing cell division in PC-3 cells; it appears to be partially reversing the molecular signature of metastatic behaviour. A compound that can promote a noninvasive epithelial phenotype in highly metastatic cancer cells is doing something qualitatively different from a simple cytostatic agent.

The Honest Complication — What Happened to Healthy Cells

This is where the study delivers a finding that demands careful consideration rather than celebration.

The noncancerous prostate epithelial cell lines — PWR-1E and RWPE-1 — were not spared by CBD. Under serum deprivation conditions, these healthy cells were slightly more sensitive to CBD than the cancer cell lines, with IC50 values of 0.9 micromolar and 1.1 micromolar respectively. And when PWR-1E cells were examined under fluorescence microscopy, the mechanism of that reduced viability was apoptosis — programmed cell death — rather than the proliferation inhibition seen in cancer cells.

The Healthy Cell Finding — Context Is Everything

This result differs from some other cancer types where CBD preferentially spares normal cells. Several points are essential context. First, the experiments on healthy cells were conducted without serum, which artificially increases CBD's potency. Second, the IC50 values in healthy cells under no-serum conditions are within the range that is reported safe and well-tolerated in humans — several studies report that CBD doses up to 1500 mg per day are safe in human subjects, and cannabis-based medicines are approved for clinical use with established safety profiles. Third, immortalised cell lines — including the healthy lines used here — are artificially transformed and do not perfectly represent true normal human prostate cells. The authors acknowledge all of these caveats directly and call for deeper investigation rather than drawing premature conclusions.

This is the kind of finding that separates rigorous science from promotional science. The researchers did not bury this result or explain it away. They presented it, contextualised it honestly, and identified it as a direction for further investigation. The practical conclusion is not that CBD is unsafe — it is that understanding the difference in how CBD affects cancer versus normal prostate cells requires more work, including in vivo studies and more physiologically realistic cell models.

Connecting This Week to the Broader Series

Three weeks ago we mapped eight cancer types and five mechanisms across the broad cannabis-cancer literature. Prostate cancer was one of them, with the finding that cannabis extract and CBD increased caspase activity, upregulated TP53 and Bax, and reduced tumour size in mouse experiments when combined with cisplatin. This study goes deeper into the prostate cancer story — it adds mechanistic detail at the level of individual cell cycle proteins, identifies a receptor-independent mechanism of action, and provides the first direct evidence that CBD reduces CDK1 expression in cancer.

Last week's ovarian cancer study introduced the PTEN/PI3K/AKT/mTOR axis as a central mechanism of CBD:THC combination action, and showed that AKT phosphorylation was one of the primary targets. This week's study confirms AKT phosphorylation reduction in a different cancer by CBD alone — strengthening the case that this is not a cell-line-specific quirk but a genuine feature of how CBD interacts with cancer cell signalling.

The E-cadherin finding also connects to the broader anti-metastatic picture. Across this series, we have documented cannabinoids reducing invasion through TIMP-1 upregulation in lung cancer, through CSF-1 depletion in melanoma, and now through E-cadherin restoration in prostate cancer. Each mechanism is distinct, which suggests cannabinoids are not hitting a single anti-metastatic target but are capable of disrupting the metastatic programme through multiple independent routes depending on the cancer type.

"CBD is not simply a blunt cytotoxic agent. In prostate cancer cells, it appears to engage specific molecular machinery — cell cycle checkpoints, AKT signalling, and epithelial identity markers — in ways that go considerably beyond what the broader public discussion of cannabis and cancer has yet caught up with."

What Comes Next

The authors are explicit about what this study does and does not establish. It is an in vitro study — 2D cell culture models that do not capture the complexity of a living tumour. The next steps they identify include testing in 3D cell culture models, which better reflect the architecture of real tumours, and in animal models, which would reveal whether the effects observed in cell culture translate to a living organism with intact vasculature, immune function, and drug pharmacokinetics.

The receptor question also remains open. Knowing that CBD's effects are not mediated by CB1, CB2, TRPV1, or GPR55 is a useful piece of negative information, but it does not yet tell us which target is responsible. Identifying that target would clarify the mechanism, inform dosing strategies, and potentially enable the design of CBD analogues with enhanced specificity or potency against prostate cancer cells.

For a cancer that kills hundreds of thousands of men annually, and for which metastatic and castration-resistant forms remain essentially without curative options, the data presented in this study represents a credible early-stage signal worth following. The cell cycle proteins are real. The AKT effect is real. The E-cadherin shift is real. The path from cell culture to clinical application is long and uncertain, but this study makes the journey worth attempting.

Cannabis Research Coverage — The Grower's Connect

Source Study: O'Reilly E, Khalifa K, Cosgrave J, Azam H, Prencipe M, Simpson JC, Gallagher WM, Perry AS. Cannabidiol Inhibits the Proliferation and Invasiveness of Prostate Cancer Cells. Journal of Natural Products 2023, 86, 2151–2161. doi:10.1021/acs.jnatprod.3c00363 — UCD School of Biology and Environmental Science and Cancer Biology and Therapeutics Laboratory, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland. Published September 13, 2023. Funded in part by the Irish Research Council and GreenLight Pharmaceuticals.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

CBD and THC Together in Ovarian Cancer Cells

CBD and THC Together in Ovarian Cancer Cells
A Combination No One Was Looking For — CBD and THC Together in Ovarian Cancer Cells | The Certified
The Grower's Connect
Research · Cannabis Science

Part of our ongoing coverage of peer-reviewed cannabis research. Last week: What the Science Actually Says About Cannabis and Cancer — a review of eight cancer types. This week: a brand new 2025 study focused specifically on ovarian cancer, and a mechanism the broader review only touched on.

Cannabis Science · Ovarian Cancer · New Research 2025

A Combination No One Was Looking For — CBD and THC Together in Ovarian Cancer Cells

A December 2025 study tested CBD and THC — separately and in combination — against two ovarian cancer cell lines, including one that resists platinum-based chemotherapy. The combination killed cancer cells selectively, left healthy cells largely unharmed, and exposed a molecular mechanism that could change how we think about cannabinoid-based therapy.

The Grower's Connect  ·  2025  ·  11 min read
~25% apoptosis in A2780 cancer cells (combination vs ~8% control)
5× lower IC50 in cancer cells vs healthy cells for CBD
10× increase in mitochondrial ROS in A2780 cells (combination)
2.5:2.5 micromolar — the sweet spot combination dose
Listen to this article A Combination No One Was Looking For — CBD and THC Together in Ovarian Cancer Cells
Audio coming soon — replace this div with your <audio> tag when ready

Last week we looked at a broad review of cannabis and cancer research — eight cancer types, five mechanisms, a body of evidence that is serious enough to warrant attention but not yet mature enough to produce clinical recommendations. One of the mechanisms that appeared repeatedly was the inhibition of a signalling pathway called PI3K/AKT/mTOR — a growth and survival axis that is overactivated in many cancers and particularly problematic in ovarian cancer.

This week a new study lands that goes directly at that mechanism. Published in Frontiers in Pharmacology in December 2025, authored by researchers at Khon Kaen University in Thailand, the paper takes two ovarian cancer cell lines — one sensitive to standard chemotherapy, one innately resistant to it — and systematically tests what cannabidiol, THC, and their combination do to each one. The results are specific, mechanistically detailed, and in several respects surprising.

Why Ovarian Cancer Is Such a Difficult Target

Ovarian cancer carries the highest rates of morbidity and mortality among all gynaecological cancers, largely because it is diagnosed late. By the time symptoms become specific enough to identify, the disease has typically progressed to an advanced stage. Over 295,000 patients were diagnosed with ovarian cancer globally in recent data, and approximately 185,000 women died from it — numbers that reflect how consistently this cancer outmanoeuvres early detection.

Standard treatment is surgery followed by platinum-based chemotherapy — cisplatin or carboplatin, which work by cross-linking DNA and triggering apoptosis in cancer cells. The problem is that ovarian cancer frequently develops resistance to these drugs. Once resistance is established, treatment options narrow dramatically and patient outcomes deteriorate. This is the clinical context that makes the search for alternative or adjunctive agents genuinely urgent, not merely academically interesting.

"One of the two cell lines in this study — SKOV3 — is innately resistant to platinum-based chemotherapy. Testing cannabinoids against it specifically is not an accident. It is a direct engagement with the hardest version of the problem."

The PI3K/AKT/mTOR pathway sits at the centre of why ovarian cancer is so hard to treat. It is overactivated in a significant proportion of ovarian cancers, and it drives cell proliferation, survival, and chemoresistance. PTEN — phosphatase and tensin homolog — is the natural brake on this pathway. In many ovarian cancers, PTEN is lost or silenced, removing that brake and allowing the pathway to run unchecked. Restoring PTEN function is therefore a legitimate therapeutic goal, and it is one the cannabinoid combination in this study appears to address.

How the Study Was Designed

The researchers worked with three cell lines. A2780 is a platinum-sensitive ovarian cancer model. SKOV3 is a platinum-resistant ovarian cancer model. IOSE80 is a non-tumorigenic ovarian epithelial cell line used to assess whether the treatments harm healthy cells. Including the non-cancer cell line is critical — it allows the researchers to measure selectivity, which is the difference between a therapeutic agent and a poison.

Compounds were tested individually at multiple concentrations across 24, 48, and 72 hours. They were also tested in combination at three ratios — 1:1, 1:2, and 1:4 CBD to THC — to assess how the interaction between the two compounds changes depending on their proportions. The Chou-Talalay method was used to calculate combination index values and determine whether the interaction between CBD and THC is synergistic, additive, or antagonistic at each ratio and effect level. This is the gold standard mathematical framework for combination drug analysis, and its inclusion gives the findings considerably more rigor than a simple cell viability comparison would provide.

The Selectivity Finding — Cancer Cells vs Healthy Cells

The first and perhaps most clinically important finding is one we touched on in last week's broader review: cannabinoids appear to be more toxic to cancer cells than to healthy ones, and by a meaningful margin.

Compound A2780 (cancer) SKOV3 (cancer) IOSE80 (healthy)
CBD (48 h IC50) 4.33 micromolar 5.07 micromolar 21.65 micromolar
THC (48 h IC50) 5.92 micromolar 5.75 micromolar 24.42 micromolar

IC50 is the concentration required to kill 50% of cells. A lower IC50 means a compound is more potent against that cell type. The cancer cell lines required four to six times less CBD or THC to achieve 50% cell death than the healthy IOSE80 cells did. This selectivity window is not enormous, but it is consistent and statistically significant, and it aligns with what the broader literature has been finding across multiple cancer types, as we documented last week.

Why the IOSE80 Result Matters

The healthy cell IC50 values — around 21 to 24 micromolar — are also well above the plasma concentrations typically achieved in living organisms following clinically relevant cannabinoid dosing. This suggests the cytotoxicity observed in healthy cells at high doses in the laboratory is unlikely to translate to equivalent harm in a real therapeutic context, though this remains to be confirmed in animal and human studies.

The Synergy Question — When Does Combining CBD and THC Help?

The combination index analysis is where this study gets genuinely interesting — and where it delivers a warning as much as a finding.

In A2780 cells at the 1:1 ratio — equal parts CBD and THC — the combination index values were 0.7, 0.5, and 0.5 at 20%, 50%, and 80% cell death respectively. A combination index below 1 indicates synergy. These numbers mean that CBD and THC at equal proportions work better together against A2780 cells than either would at equivalent doses alone, and the synergy becomes more pronounced as the desired level of cell killing increases.

In SKOV3 cells — the platinum-resistant line — the picture is more complex. At the 1:1 ratio, the combination was antagonistic at lower cell killing levels but synergistic at higher ones. This concentration-dependent switch from antagonism to synergy is not a failure of the approach; it is a signal that the interaction between CBD and THC involves multiple molecular mechanisms that engage at different thresholds. At lower concentrations, the two compounds may compete for overlapping receptor sites. At higher concentrations, their complementary pathways — mitochondrial stress, ROS generation, and PI3K/AKT/mTOR inhibition — appear to reinforce each other.

In IOSE80 healthy cells, all combination ratios showed additive to antagonistic effects — meaning the combination does not achieve synergistic toxicity against non-cancerous tissue. This is the safety finding the researchers were looking for, and it held consistently across all tested ratios and effect levels.

The Ratio Warning

Not all combinations are equal. At the 1:4 ratio — four parts THC to one part CBD — the combination became strongly antagonistic in A2780 cells, with combination index values rising to 1.2, 2.7, and 6.9 at increasing effect levels. In SKOV3 cells, the antagonism at this ratio was even more pronounced, with combination index values as high as 15.8. The wrong ratio does not merely fail to help — it actively reduces efficacy below what either compound would achieve alone. This is one of the most practically important findings in the study and a direct argument for precision in dosing and ratio design in any future therapeutic application.

What the Combination Actually Does to Cancer Cells

Beyond the cytotoxicity measurements, the researchers investigated what is actually happening inside the cells when the combination is applied. The findings span four distinct biological effects.

G0/G1 Cell Cycle Arrest

Both CBD and THC individually caused significant accumulation of cells in the G0/G1 phase of the cell cycle — the checkpoint before DNA replication begins. The combination at 2.5:2.5 micromolar pushed this effect further than either compound alone. Crucially, the same treatment did not significantly alter cell cycle distribution in healthy IOSE80 cells, confirming selective targeting of cancer cell proliferation.

Apoptosis Induction

The combination treatment induced approximately 25% apoptosis in A2780 cells and approximately 28% in SKOV3 cells — substantially higher than either CBD or THC alone at equivalent concentrations. In healthy IOSE80 cells, the combination produced only a slight increase in apoptosis. The cell death observed was predominantly apoptotic rather than necrotic, which is therapeutically preferable as apoptosis avoids the inflammatory collateral damage associated with necrosis.

Mitochondrial Membrane Depolarisation

Using JC-1 staining, the researchers measured changes in mitochondrial membrane potential — a key early indicator of apoptosis. The combination produced the most pronounced mitochondrial depolarisation in both cancer cell lines, corresponding to a higher proportion of disrupted mitochondria compared to individual treatments. Mitochondrial disruption leads to the release of pro-apoptotic factors including cytochrome c, which activates caspases and initiates programmed cell death.

Mitochondrial ROS Generation

The combination produced a more than tenfold increase in mitochondrial reactive oxygen species in A2780 cells and more than a threefold increase in SKOV3 cells compared to the control. Elevated ROS at these levels causes oxidative damage to DNA, proteins, and lipids, pushes cells beyond their oxidative tolerance threshold, and further amplifies the mitochondrial apoptotic pathway. This ROS surge is one of the mechanisms that explains the synergistic killing observed in the combination index analysis.

The researchers also assessed migration and invasion — two behaviours that are prerequisites for metastasis. Using Transwell assays with Matrigel, they found that CBD and THC individually reduced both migration and invasion in A2780 and SKOV3 cells, and the combination suppressed both behaviours more strongly than either compound alone. This anti-metastatic finding adds a dimension beyond direct cell killing: even if some cancer cells survive the treatment, their capacity to spread may be significantly impaired.

The Molecular Mechanism — PI3K, AKT, mTOR, and PTEN

This is the section of the study that connects most directly to last week's broader review. We noted then that the PI3K/AKT/mTOR signalling axis is frequently overactivated in ovarian cancer and that cannabidiol had shown consistent ability to inhibit this pathway in cholangiocarcinoma and other cancer types. This study provides the most detailed picture yet of how that inhibition operates in ovarian cancer specifically.

Western blot analysis — a technique for measuring protein levels and activity — revealed the following after treatment with CBD, THC, and their combination at 2.5:2.5 micromolar:

PI3K / AKT / mTOR / PTEN — What Changed

  • Total PI3KCA The combination treatment notably suppressed total PIK3CA expression in both cell lines compared to the control and to individual treatments. CBD and THC alone had less effect on total protein levels.
  • Total AKT and mTOR Total protein levels of AKT and mTOR did not change significantly with any treatment. The pathway is not being dismantled — it is being switched off at the level of activation.
  • Phospho-PI3K, Phospho-AKT, Phospho-mTOR All three phosphorylated forms — which represent the active, cancer-driving state of the proteins — were significantly reduced by CBD, THC, and most powerfully by their combination. The combination produced the most striking inhibitory effect on all three.
  • Total PTEN PTEN protein levels increased with CBD treatment and with the combination. This is the tumour suppressor that normally brakes the PI3K pathway — its upregulation is a direct counter to oncogenic signalling.
  • Phospho-PTEN The phosphorylated form of PTEN — which locks it in an inactive configuration — was significantly reduced by the combination. Less phospho-PTEN means more active PTEN, which means a stronger brake on the PI3K/AKT/mTOR axis.

The significance of the PTEN finding warrants a moment of explanation. PTEN normally works by removing a phosphate group from a molecule called PIP3, converting it to PIP2. This conversion blocks the signal that activates AKT. When PTEN is phosphorylated at specific sites on its C-terminus — serine 380, threonine 382, and threonine 383 — it folds into a closed configuration that is more stable but less catalytically active. It is still present in the cell, but it is not doing its job.

What the combination treatment appears to do is increase the total amount of PTEN protein while simultaneously reducing its phosphorylation — shifting more PTEN into the open, active configuration. The result is a tumour suppressor that is not only more abundant but also more functional. Combined with the direct reduction in PI3K, AKT, and mTOR phosphorylation, this represents a two-pronged attack on the oncogenic pathway: switching off the accelerator while reactivating the brake.

"The combination doesn't just block the pathway that drives cancer cell survival. It restores the body's own mechanism for suppressing it. That is a different and potentially more durable kind of intervention."

Connecting This to What We Already Knew

Last week's review of the broader cancer literature documented five mechanisms through which cannabinoids appear to attack cancer cells: apoptosis induction, autophagy induction, tumour regression, inhibition of proliferation, and suppression of invasion and angiogenesis. This study confirms four of those five in a single, tightly controlled experiment on a specific cancer type, and it adds mechanistic depth to each of them.

It also extends last week's observation about cannabidiol as an adjunct that amplifies existing treatments. We noted, in the context of liver cancer, that CBD enhanced the anticancer activity of cabozantinib. In the context of ovarian cancer, the same principle applies — but here the combination is cannabinoid-to-cannabinoid rather than cannabinoid-to-chemotherapy. CBD and THC appear to engage complementary molecular pathways that, at the right ratio and concentration, produce effects neither achieves alone.

The researchers themselves draw an explicit parallel to previous work showing that CBD and THC combinations can achieve synergistic or additive anti-cancer effects in other cancer models, including glioma, where the combination with temozolomide produced the most promising clinical trial results in the broader cannabis-cancer literature — the 83% one-year survival rate in glioblastoma patients we highlighted last week.

What This Study Cannot Tell Us

This is rigorous in vitro science, and the authors are honest about its limits. The cells tested in a laboratory dish do not capture the complexity of a living tumour — its vasculature, its immune microenvironment, the variation in oxygenation and nutrient availability across different regions, and the pharmacokinetic reality of how cannabinoids are absorbed, distributed, metabolised, and eliminated in a living body.

The study also did not include a full ADMET assessment — the analysis of absorption, distribution, metabolism, excretion, and toxicity that would be required before a clinical application could be seriously planned. The authors acknowledge this gap and call for in silico and in vitro pharmacokinetic modelling as next steps. And critically, no in vivo work was conducted in this study. The molecular findings need validation in animal models before the translation to clinical relevance can be claimed.

The ratio dependence of the synergy is also a practical constraint that will not be simple to address. The difference between the 1:1 ratio — which produced synergy in A2780 cells — and the 1:4 ratio — which produced strong antagonism in both cancer lines — is not a minor dosing question. It is a fundamental design problem for any therapeutic formulation. Getting this wrong would not merely reduce efficacy; it would actively undermine it.

What It Means for How We Think About the Plant

Something emerges from looking at this study alongside last week's broader review: the cannabis plant may contain a therapeutic system that is greater than any of its individual parts. CBD alone inhibits the PI3K/AKT/mTOR pathway. THC alone does so less consistently. Together, at the right ratio, they inhibit the pathway more powerfully than either does alone and simultaneously restore PTEN function — a combination of effects that neither achieves independently.

This is a more sophisticated version of what the cannabis research community has long described as the entourage effect — the idea that compounds in the plant work together in ways that individual molecules cannot replicate alone. What this study adds is a mechanistic explanation for at least one instance of that interaction, at a level of biological detail that moves the concept from intuition into evidence.

For growers and producers, the implication is one we have raised before in this series: the chemical profile of a cannabis variety matters, and not just for the reasons the commercial market currently emphasises. The ratio of CBD to THC in a cultivar is not merely a regulatory or psychoactivity consideration. It is, according to this research, a variable that determines whether two compounds in the plant will work synergistically or antagonistically against cancer cells. That is a more consequential version of the CBD-to-THC ratio conversation than the industry is currently having.

Cannabis Research Coverage — The Grower's Connect

Source Study: Tong S, Loilome W, Namwat N, Klanrit P, Wangwiwatsin A, Win ZZ, Koyabuth P and Chumworathayi B. Selective anti-cancer effects of cannabidiol and delta-9-tetrahydrocannabinol via PI3K/AKT/mTOR inhibition and PTEN restoration in ovarian cancer cells. Frontiers in Pharmacology 2025, 16:1693129. doi:10.3389/fphar.2025.1693129 — Department of Systems Biosciences and Computational Medicine and Department of Obstetrics and Gynaecology, Faculty of Medicine, Khon Kaen University, Thailand. Published 15 December 2025.
The Certified — The Grower's Connect  ·  thecertified.co.za
Posted on by

What the Science Actually Says About Cannabis and Cancer

cannabis and cancer
What the Science Actually Says About Cannabis and Cancer | The Certified
The Grower's Connect
Research · Cannabis Science

Part of our ongoing coverage of peer-reviewed cannabis research. Previously: When the System Breaks — What Fibromyalgia Reveals About the Endocannabinoid System. This week: what a comprehensive 2024 review says about cannabis compounds and cancer.

Cannabis Science · Oncology · Review 2024

What the Science Actually Says About Cannabis and Cancer

A 2024 peer-reviewed review compiled research across eight cancer types — lung, liver, prostate, breast, melanoma, glioblastoma, cholangiocarcinoma, and head and neck cancer. Here is a careful reading of what the evidence shows, and what it does not.

The Grower's Connect  ·  2025  ·  12 min read
8 cancer types with documented cannabinoid activity
5 distinct anticancer mechanisms mapped
83% one-year survival rate in glioblastoma trial (THC+CBD+TMZ)
157 studies assessed in the source review
Listen to this article What the Science Actually Says About Cannabis and Cancer

There is a version of the cannabis-and-cancer conversation that happens in wellness circles, in dispensaries, and in anxious family group chats, and it is mostly driven by anecdote, hope, and incomplete information. There is a different version happening in peer-reviewed journals, and it is considerably more interesting — and considerably more careful — than either the enthusiastic claims or the dismissive counter-claims that dominate public discourse.

A review published in November 2024 in the International Journal of Molecular Sciences, authored by researcher Bozena Bukowska at the University of Lodz in Poland, compiled and assessed 157 studies on the biologically active compounds of Cannabis sativa and their effects on disease. The section that commands the most data — and the most nuance — covers cancer. What follows is a careful reading of those findings, organised by cancer type and written to reflect both what the evidence shows and what it does not yet prove.

Why Cannabinoids Are Being Studied in Oncology at All

Cancer can alter the endocannabinoid system — the body's own network of receptors and signalling molecules that regulate everything from pain to immune response to cell survival. THC and CBD interact with this system in ways that have measurable effects on cancer cells in the laboratory. Cannabinoids appear to influence several of the fundamental processes that make cancer dangerous: how quickly cancer cells divide, whether they die when they should, whether they spread to new locations, and whether they can recruit new blood vessels to feed tumour growth.

The research in this review draws on three levels of evidence. In vitro studies test compounds on cancer cells in laboratory dishes. In vivo studies test them in living animals, usually mice. Clinical trials test them in human patients. Each level carries different weight, and the distinctions matter enormously. A compound that kills cancer cells in a dish has cleared a very low bar. A compound that shrinks tumours in mice has cleared a higher one. A compound that improves survival in human patients has cleared the bar that actually matters.

"Cannabinoids have demonstrated anticancer properties across eight cancer types and five distinct biological mechanisms. The question is no longer whether the effect exists in the laboratory — it is whether it translates to the clinic."

Lung Cancer — Multiple Mechanisms, Consistent Direction

The evidence in lung cancer is among the most detailed in the review, with several independent research teams arriving at consistent conclusions through different experimental approaches.

Cannabidiol was shown to decrease the viability of human lung cancer cells by triggering apoptosis — the process by which cells destroy themselves in an orderly, programmed way. The mechanism involved the upregulation of two proteins: COX-2 and PPAR-gamma. When cancer cells treated with cannabidiol were examined, elevated levels of COX-2-dependent prostaglandins were found. These prostaglandins moved PPAR-gamma into the cell nucleus, where it triggered apoptotic cell death. In animal experiments using lung cancer cells implanted in nude mice, the same mechanism appeared to operate in a living organism, and tumour regression was observed — an important step in establishing biological relevance beyond the laboratory dish.

A separate line of investigation looked at cancer invasion — the ability of cancer cells to spread into surrounding tissue, which is one of the features that makes cancer deadly. Cannabidiol, THC, and a stable analogue of the endocannabinoid anandamide all slowed the invasion of human lung carcinoma cells. The mechanism traced back to a protein called TIMP-1, a tissue inhibitor of metalloproteinases, whose elevated expression appeared to mediate the anti-invasive effect. The authors of that study went so far as to recommend cannabinoids in the treatment of highly invasive cancers.

An in vivo study using a Lewis lung cancer grafted mouse model found that Cannabis sativa essential oil significantly inhibited tumour growth, reduced tumour inflammatory markers including TNF-alpha and IL-6, and increased the numbers of immune-related T lymphocytes — suggesting the anti-tumour effect may in part operate through the immune system rather than by acting directly on cancer cells alone.

Liver Cancer — CBD Amplifying an Existing Drug

In hepatocellular carcinoma — the most common form of liver cancer — researchers examined what happened when cannabidiol was combined with cabozantinib, a multi-kinase inhibitor already used in cancer treatment. Cannabidiol increased the death of apoptotic cells caused by cabozantinib through the phosphorylation of p53, a well-known tumour suppressor protein, regulated by endoplasmic reticulum stress in liver cancer cells.

Why This Matters

This finding points toward cannabidiol's potential value not as a standalone cancer treatment but as an agent that amplifies the effects of existing chemotherapy. This is a different — and potentially more immediately actionable — therapeutic model than the one most commonly discussed in public conversations about cannabis and cancer.

Prostate Cancer — Cell Death Through Multiple Pathways

Research on prostate cancer cells found that a combination of cannabis extract, cannabidiol, and cisplatin caused antiproliferation of PC3 cancer cells by increasing the activity of caspase 3 and caspase 7 — enzymes that execute the apoptotic process inside cells. Silencing a protein called RBBP6 produced apoptotic changes alongside upregulation of TP53 and Bax expression and downregulation of Bcl-2. This combination — more pro-apoptotic signalling, less anti-apoptotic protection — pushes cells toward death. In mouse experiments, tumours decreased in size after treatment with cisplatin and cannabidiol.

A Phase I clinical trial using Epidiolex — the pharmaceutical-grade cannabidiol preparation approved by the FDA — enrolled 18 patients with biochemically recurrent prostate cancer. At 800 milligrams per day, it was well tolerated with an acceptable safety profile. The authors were clear about the limitations: short treatment duration, small sample size, no comparator group. This is early human data, not a clinical recommendation, but it establishes that the compound can be administered to prostate cancer patients without obvious acute safety problems.

Breast Cancer — Blocking Proliferation and Colony Formation

Research on breast cancer cells documented cannabidiol blocking proliferation through reactive oxygen species-mediated endoplasmic reticulum stress. Cannabinol — a cannabinoid that receives comparatively little commercial attention — was found to induce apoptosis in breast cancer cell lines by downregulating p21 and p27, and arresting the cell cycle in the G1 or S phase by reducing CDK1, CDK2, and cyclin E1 levels.

Cannabigerol, commonly known as CBG, was found to reduce the amount of macrophages associated with tumours and deplete colony-stimulating factor 1 secretion from melanoma cells — a mechanism with relevance to breast cancer given that CSF-1 plays a role in tumour microenvironment regulation across multiple cancer types. The review also notes that synergistic effects have been observed for the combination of cannabidiol with cannabichromene or THC, where small concentrations of cannabinoid combinations can replicate the effect of much higher doses of either compound alone.

Melanoma — Tumour Shrinkage in Animals, Apoptosis in Cells

The melanoma evidence is both mechanistically detailed and, in terms of animal data, among the more striking in the review.

CBG + Immune Checkpoint Therapy

Cannabigerol inhibited tumour progression and reduced tumour-associated macrophages. When combined with anti-PD-L1 therapy, tumour progression further reduced, survival increased, and cytotoxic T cell infiltration rose — via depletion of colony-stimulating factor 1 secretion by melanoma cells.

PHEC-66 Extract — Three Cell Lines

A Cannabis sativa extract triggered apoptosis in three melanoma cell lines. It increased pro-apoptotic markers including Bax, decreased anti-apoptotic markers including Bcl-2, caused DNA fragmentation, and arrested cell progression at the G1 cell cycle control point.

CBD at 5 mg/kg — Mouse Model

Mice with subcutaneously implanted melanoma tumours treated with cannabidiol showed significantly smaller tumour sizes compared to controls. Treated mice also showed improved quality of life and movement, and cannabidiol appeared better tolerated than cisplatin.

THC + CBD — Metastatic Melanoma

Cannabinoids depleted cell viability across multiple melanoma cell lines in a concentration-dependent manner by releasing mitochondrial cytochrome c and activating multiple caspases. In mouse experiments, tumour growth was substantially reduced and potency was comparable to trametinib, an approved targeted therapy.

A further study found that a mixture of THC and CBD triggered apoptosis in human melanoma cells by upregulating several genes including DNA damage-induced transcript 3 and E2F transcription factor 1, while inhibiting ERK1 and ERK2 signalling pathway phosphorylation — responsible for regulating cell proliferation. The mixture also disrupted melanoma cell migration.

Glioblastoma and Brain Cancer — The Most Advanced Clinical Evidence

Glioblastoma is the most aggressive form of brain cancer, and it is here that the cannabis-cancer research has produced its most clinically significant result.

The Glioblastoma Phase II Trial — Key Numbers

  • 21 adult patients with glioblastoma enrolled in a Phase II clinical trial.
  • Patients taking THC and CBD alongside temozolomide achieved an 83% one-year survival rate.
  • Median survival in the cannabinoid group: over 662 days.
  • Patients receiving temozolomide alone achieved a 44% one-year survival rate.
  • Median survival in the control group: 369 days.

These are not marginal differences. They are the kind of numbers that, if replicated in larger trials, would change clinical practice. The biological mechanisms underlying these effects have been studied extensively in the laboratory. Cannabidiol in human and canine glioblastoma cells appears to induce cell death through dysregulation of calcium homeostasis and mitochondrial activity. Synthetic cannabinoids induce autophagy and mitochondrial apoptotic pathways in human glioblastoma cells regardless of deficiencies in TP53 or PTEN tumour suppressors — which matters because those deficiencies often make glioblastoma resistant to standard treatments.

Cannabidiol was also found to trigger autophagy in neuroblastoma cells by regulating the phosphorylation of ERK1 and ERK2, as well as AKT kinases — through a route independent of the mTORC1 pathway. This is relevant because mTOR-independent autophagy is less likely to be blocked by resistance mechanisms that cancer cells commonly develop.

The review also notes that lignanamides — phenylpropionamide derivatives found in Cannabis sativa seeds — significantly inhibited proliferation in a U-87 glioblastoma cell line by inducing apoptosis and suppressing autophagic cell death. This is a reminder that the anticancer chemistry of cannabis extends well beyond the cannabinoids alone. On the anti-angiogenesis side, local administration of a cannabinoid compound in mice inhibited the angiogenesis of malignant gliomas, producing small and impermeable blood vessels in treated tumours, compared to large and porous ones in untreated tumours.

Cholangiocarcinoma — Autophagy as the Primary Mechanism

In human cholangiocarcinoma cells — cancer of the bile ducts — cannabidiol upregulated LC3BII, a key marker of autophagy induction, while downregulating p62, a protein whose reduction indicates that the autophagy process is proceeding. Cannabidiol also inhibited the PI3K, AKT, and mTOR signalling pathways — a central growth and survival axis in many cancers — pushing cells toward autophagic death rather than continued proliferation.

The review also noted that essential oils from a Cannabis sativa cultivar called Tisza showed particularly marked cytotoxicity in cholangiocarcinoma cells in vitro — suggesting that the terpene and terpenophenol profile of the plant, not just its cannabinoids, may contribute to anticancer effects in this cancer type.

Head and Neck Cancer — CBD as a Sensitiser

In head and neck squamous cell carcinoma, cannabidiol increased the expression of genes coding for Beclin and LC3II — two proteins fundamental to the initiation of autophagy. The same study found that cannabidiol enhanced the cytotoxicity of anti-cancer drugs in these cell lines, pointing toward its potential value as an agent that sensitises cancer cells to treatment rather than acting alone. A synergistic effect was specifically documented for the combination of CBD with cannabichromene or THC, where small concentrations of the combination replicated the effect of much higher doses of either compound in isolation.

The Five Mechanisms — How Cannabinoids Attack Cancer Cells

Across all eight cancer types, the research maps onto five distinct biological mechanisms.

Five Mechanisms of Anticancer Activity

  • Apoptosis Induction Triggering programmed cell death in cancer cells that have lost their normal capacity to self-destruct. Multiple cannabinoids across multiple cancer types operate through caspase activation, mitochondrial cytochrome c release, and alterations in the Bcl-2 family of proteins.
  • Autophagy Induction Activating the cell's internal recycling and self-destruction machinery, leading to death through a pathway distinct from classical apoptosis. Cannabidiol shows consistent autophagy-inducing properties across liver, bile duct, brain, and head and neck cancer cells.
  • Tumour Regression Reduction in tumour size observed in animal models, occurring through combinations of direct cancer cell killing, immune modulation, and reduction of pro-inflammatory signalling within the tumour environment.
  • Anti-Proliferation Slowing the rate at which cancer cells divide, through interference with cell cycle checkpoints and growth signalling pathways including ERK1 and ERK2.
  • Anti-Invasion / Anti-Angiogenesis Preventing cancer cells from spreading into surrounding tissue and blocking the formation of new blood vessels that would otherwise feed tumour growth. The TIMP-1 mechanism in lung cancer and the inhibition of vascular endothelial growth factor in glioma models both fall into this category.

The Honest Limitations

An analysis of 207 preclinical articles, including 77 unique case reports, found no strong clinical trial data confirming that Cannabis sativa compounds have proven benefits against cancer in humans across the full range of cancer types studied in the laboratory. The glioblastoma Phase II trial is the exception — a genuinely promising result, but from a group of only 21 patients.

The Translation Problem

Preclinical studies on cannabinoids are most commonly conducted on animals whose metabolism, immune systems, and physiology differ significantly from those of humans. Doses that are safe and effective in animals may be toxic or ineffective in humans. Additionally, many preclinical studies fail to account for the considerable variation in age, sex, lifestyle, diet, health status, genetics, and medications between patients. Cannabinoids can also inhibit drug-metabolising enzymes, potentially altering the pharmacokinetics of co-administered anticancer drugs in ways that could enhance their effect or increase their toxicity. Standardisation of cannabis extract composition — which varies considerably by variety, geography, and isolation method — remains a significant challenge.

None of this is a reason to dismiss what the laboratory research shows. It is a reason to take it seriously enough to pursue it through the rigorous clinical trial process that will ultimately determine whether cannabinoids earn a formal place in cancer treatment protocols.

What This Means in Practice

The research picture emerging from this review is not one of cannabis as a cure for cancer. It is a picture of a plant producing biologically active compounds that interact with fundamental cancer cell processes in ways that are scientifically credible and, in several cases, reproduced across multiple independent research groups.

The most honest summary of where the evidence stands is this: cannabinoids have demonstrated anticancer properties in laboratory settings across a striking range of cancer types and through five distinct mechanisms. The one clinical trial that has tested a cannabinoid combination alongside standard chemotherapy in brain cancer produced results that are genuinely encouraging. The field now needs larger, better-powered, properly randomised clinical trials to determine which cancers, which compounds, which doses, and which patient populations will actually benefit.

That work is difficult, expensive, and complicated by regulatory frameworks that still treat cannabis as a controlled substance in most jurisdictions. But the scientific case for pursuing it is no longer speculative. It is grounded in a growing body of mechanistic evidence that this review helps to organise and make visible.

Cannabis Research Coverage — The Grower's Connect

Source Study: Bukowska, B. Current and Potential Use of Biologically Active Compounds Derived from Cannabis sativa L. in the Treatment of Selected Diseases. International Journal of Molecular Sciences 2024, 25, 12738. doi:10.3390/ijms252312738 — Department of Biophysics of Environmental Pollution, Faculty of Biology and Environmental Protection, University of Lodz, Poland. Published 27 November 2024.
The Certified — The Grower's Connect  ·  thecertified.co.za