Substance evidence
Cannabis and THC
What the controlled evidence shows, separated from the policy argument.
What Its Legal Status Actually Means
Read this before anything below it. Legal to sell is not the same fact as reviewed, verified, or approved.
Botanical cannabis has never been FDA-approved for any psychiatric indication. Its federal scheduling changed partially in 2026 and is still unsettled: a DEA/DOJ final rule effective 28 April 2026 (Federal Register document 2026-08176) moved two narrow categories — marijuana contained in an FDA-approved drug product, and marijuana subject to a state medical marijuana license — from Schedule I to Schedule III, and 21 CFR 1308.13(g) now lists them there. Everything else, including adult-use and recreational cannabis, remains in Schedule I under 21 CFR 1308.11(d), alongside naturally occurring tetrahydrocannabinols. A separate proposal to reschedule marijuana broadly to Schedule III is still pending: DEA published a notice of hearing on 28 April 2026 setting proceedings to begin 29 June 2026, and as of 18 August 2026 no final rule broadly rescheduling marijuana had been published. Meanwhile most US states run medical and/or adult-use programmes whose products are regulated by state, not federal, standards. Some pharmaceutical cannabinoids (for example dronabinol) are separately FDA-approved for non-psychiatric uses such as chemotherapy-induced nausea and AIDS-related anorexia.
Quoted whole from the 2026-08-18 study harvest. Not summarized, not shortened.
What the Research Shows
5 records from the 2026-08-18 harvest, each checked against PubMed and Europe PMC on that date. How a study was designed, how many people were in it, and who paid for it are printed above what it found, because those three facts decide how much the finding is worth.
Study 1 · 2026
- Meta-analysis of randomized trials
- 2,477 participants
- Top-tier journal
- Independently funded
- Preregistered
- Declared conflicts of interest
gold standard98/100Top of the evidence hierarchy, independently funded.
Across 54 randomised trials and 2,477 participants, cannabinoids showed no significant benefit for anxiety, PTSD, psychotic disorders, anorexia nervosa, or opioid use disorder, and there were no randomised trials at all of cannabinoids for depression. Small effects were seen for cannabis withdrawal (SMD -0.29), tic severity in Tourette syndrome (SMD -0.68), sleep time in insomnia, and autistic traits, all at low certainty; adverse events were more frequent with cannabinoids (OR 1.75, number needed to harm 7).
How this record was checked
PubMed record 41856154 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, 54 trials, n=2477, and the specific effect estimates confirmed from the abstract. Funding read directly off the record's FUNDING field ("The National Health and Medical Research Council"), hence INDEPENDENT; PROSPERO registration CRD42023392718 and the declaration-of-interests statement also read off the record. Record carries an "Erratum in" notice (Lancet Psychiatry 2026;13(8):e11), not a retraction.
Study 2 · 2019
- Meta-analysis of randomized trials
- 3,067 participants
- Top-tier journal
- Independently funded
- Preregistered
- Declared conflicts of interest
gold standard98/100Top of the evidence hierarchy, independently funded.
Pooling 40 randomised trials (n=3,067) across depression, anxiety, ADHD, Tourette syndrome, PTSD, and psychosis, pharmaceutical THC produced only a very-low-certainty small improvement in anxiety among people whose primary problem was another medical condition (SMD -0.25), worsened negative symptoms of psychosis in the single trial that measured it (SMD 0.36), and did not significantly affect any other primary outcome. It roughly doubled the odds of adverse events (OR 1.99) and nearly tripled withdrawals due to adverse events (OR 2.78).
How this record was checked
PubMed record 31672337 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, 83 studies / 40 RCTs / n=3067, and the effect estimates confirmed from the abstract. Funding read off the record's FUNDING field (Therapeutic Goods Administration Australia; Commonwealth Department of Health; NHMRC; US NIH), hence INDEPENDENT; five PROSPERO registrations and the conflicts statement also read off the record. Record carries "Erratum in" and "Comment in" notices, no retraction.
Study 3 · 2019
- Case-control study
- 2,138 participants
- Top-tier journal
- Independently funded
moderate68/100Reasonable evidence with real limitations.
Read this first: This is a case-control design, so it establishes association and a dose-response pattern rather than proving causation; reverse causation (early psychotic symptoms driving heavier use) and residual confounding cannot be fully excluded, which is why the authors flag the population-attributable fractions as conditional on causality.
Comparing 901 people presenting with first-episode psychosis against 1,237 population controls across 11 European and Brazilian sites, daily cannabis use was associated with about three times the odds of psychotic disorder (adjusted OR 3.2, 95% CI 2.2-4.1) and daily use of high-potency cannabis (THC 10% or more) with nearly five times the odds (OR 4.8, 2.5-6.3). Assuming causality, removing high-potency cannabis would prevent an estimated 12.2% of first-episode psychosis across all sites, 30.3% in London, and 50.3% in Amsterdam.
How this record was checked
PubMed record 30902669 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, 901 cases and 1,237 controls (n=2,138 total), and all odds ratios and population-attributable fractions confirmed from the abstract. Funding read off the record's FUNDING SOURCE field (Medical Research Council, EU FP7, São Paulo Research Foundation, NIHR Biomedical Research Centres, Wellcome Trust), hence INDEPENDENT. No conflict-of-interest statement present in the record, so conflicts recorded false.
Study 4 · 2019
- Systematic review of observational studies
- 23,317 participants
- Top-tier journal
- Independently funded
- Declared conflicts of interest
strong83/100Well-supported by good-quality research.
Read this first: One co-author (Ware) became an employee of Canopy Growth Corporation, a licensed cannabis producer, after the work was completed, and the senior author discloses an unrelated cannabidiol grant involving Aurora Cannabis; both were disclosed. The pooled estimates come from observational studies, so residual confounding by shared risk factors for cannabis use and depression cannot be excluded.
Pooling 11 longitudinal studies covering 23,317 people, cannabis use before age 18 was associated with modestly higher odds of major depression in young adulthood (OR 1.37, 95% CI 1.16-1.62) and of suicidal ideation (OR 1.50, 1.11-2.03) and suicide attempt (OR 3.46, 1.53-7.84); the association with anxiety was not statistically significant (OR 1.18, 0.84-1.67). Individual-level risk is moderate to low, but the authors note that at population scale this translates into a large number of affected young people.
How this record was checked
PubMed record 30758486 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, 11 studies, n=23,317, and all four odds ratios confirmed from the abstract. PMC record 6450286 fetched the same day carries the Funding/Support statement (Canadian Institutes of Health Research knowledge synthesis grant 147991 and the Quebec Network on Suicide, Mood Disorders and Related Disorders; funders had no role), hence INDEPENDENT, plus the conflict disclosures quoted above. Record carries an "Erratum in" notice, no retraction.
Study 5 · 2016
- Systematic review of observational studies
- 66,816 participants
- Reputable journal
- Funding not established
moderate59/100Reasonable evidence with real limitations.
Read this first: Built entirely from observational studies with heterogeneous definitions of "heavy" use; the pooled odds ratio was generated by simulating individual data points from summary statistics, a method that depends on assumptions about the underlying distributions.
Across 10 studies and 66,816 people, the heaviest cannabis users had almost four times the odds of schizophrenia and related psychotic outcomes compared with non-users (OR 3.90, 95% CI 2.84-5.34), and every included study showed higher risk at higher levels of use. The consistent dose-response gradient is what makes this association hard to dismiss as confounding alone, though the authors stop short of claiming proof of causation.
How this record was checked
PubMed record 26884547 fetched via NCBI efetch 2026-08-18; title, authors, journal, year, DOI, 18 studies reviewed / 10 meta-analysed, n=66,816, and OR 3.90 (2.84-5.34) confirmed from the abstract. PMC record 4988731 fetched the same day returns front matter and abstract only with no readable funding statement, so funding is recorded UNKNOWN despite Europe PMC listing MRC and NIHR grant tags against the record, and independence is left unchecked.
The Risks
Nobody checks this purchase the way a prescription is checked. No prescriber reviews it against the rest of what you take, no pharmacist screens the interaction, and no regulator confirms the dose in the capsule before it is sold. That is why this section sits here at full length rather than as a footnote.
What the paragraph below covers:
- Suicidal thoughts or behavior
- Heart and blood pressure
- Psychosis and mania
- Dependence and withdrawal
- Drug interactions
- Sleep disruption
- Stomach and gut
The dose-response relationship between cannabis and psychosis is one of the better replicated findings in psychiatric epidemiology: heavier use carries roughly a three-to-four-fold increase in psychosis risk, and daily use of high-potency (THC 10% or more) product carries close to a five-fold increase. Cannabis use disorder is common — dependence, tolerance, and a withdrawal syndrome of irritability, insomnia, appetite loss, and craving. Adolescent use is prospectively associated with depression and suicidality in young adulthood. In randomised trials, THC-containing cannabinoids worsened negative symptoms of psychosis and roughly doubled the odds of adverse events and of dropping out because of them. Acute effects include anxiety and panic (a common reason people stop), impaired driving, and cannabinoid hyperemesis syndrome with chronic heavy use. THC interacts with alcohol and other CNS depressants, and daily inhaled use has been linked to cardiovascular events. Using cannabis to self-treat anxiety or depression risks worsening the condition it is meant to help.
What Is Not Known
The boundaries of the section above, in the harvest’s own words. What it excluded, why, and where it looked and found nothing. An absence of evidence is not evidence of absence, and it is not evidence of benefit either.
What Was Left Out, and Why
Quoted from the harvest, where these notes sat above the study list rather than after it. Where a note says “below” it means the studies in the section above.
- Cannabidiol-only evidence lives in cannabidiol.yaml; this file covers THC-containing cannabis and pharmaceutical cannabinoids.
- Individual state-registry and dispensary self-report surveys of "medical cannabis for anxiety/PTSD" excluded: they are uncontrolled, self-selected, and subsumed by the two Lancet Psychiatry meta-analyses below.
- Hsu 2026 JAMA clinical review (PMID 41296368) was verified but excluded as a narrative review that would add nothing the meta-analyses do not already carry.
- The honest summary: the strongest evidence about cannabis and mental health is about harm, not benefit. That asymmetry is deliberate and is what the record shows.
The Retraction Check
PubMed efetch records for all five PMIDs (41856154, 31672337, 30902669, 30758486, 26884547) inspected 2026-08-18 for "Retraction in" flags; none present. Black 2019 and Gobbi 2019 carry "Erratum in" notices and Wilson 2026 carries one; these are corrections, not retractions, and are noted in the records below.
Questions for a Prescriber or Pharmacist
This page does not tell anyone to take Cannabis and THC or to avoid it. It is not able to: it does not know what else you take, what you have tried, or what you are treating. These are the questions each study above raises, written to be asked out loud.
- Given that the 2026 trial review found no benefit for anxiety, PTSD, or psychosis and no depression trials at all, what evidence-based option should I be on instead of self-medicating with cannabis?
- This review found THC did not help any mental-health outcome but doubled the odds of side effects — if I am using cannabis for my mood, what are we actually trading away?
- Given my family history and the potency of what is sold now, what is my personal risk of a psychotic episode if I keep using cannabis daily?
- My teenager is using cannabis — what does the depression and suicide-risk evidence mean for them specifically, and what should we do about it now?
- If risk rises with how much I use, is cutting down meaningfully protective, or does the evidence only support stopping?
And the one to ask at the counter, whatever the answers above turn out to be: given everything I am already taking, what would you want to know about Cannabis and THC before I put it in the same body?
Where This Page Comes From
Transcribed from the study-harvest-2026-08-18 record for cannabis-thc, built into this page by scripts/supplement-ingest.mjs on 2026-09-07. Nothing here is fetched at page load, and nothing here was written by a model without a citation behind it.
| Source file | study-harvest/2026-08-18/cannabis-thc.yaml |
|---|---|
| Source repo | REPTechnologies/avalo-backend |
| SHA-256 | 9d7372ad250da7d426199feafe6e3021eb6faf267b2a1743bcb585d5886bd6db |
| Also searched as | marijuana, weed, THC, delta-9-tetrahydrocannabinol, medical cannabis, dronabinol, nabiximols |
The Other Substances
- 5-HTP
- Ashwagandha
- Cannabidiol (CBD)
- Creatine
- Kratom
- L-Theanine
- Magnesium
- Melatonin
- Methylene Blue
- Microdosing
- N-Acetylcysteine (NAC)
- Omega-3
- Phenibut
- SAMe
- St John’s Wort
- Valerian
Do any supplements actually work? asks the question across all of them. The full library has the medication records, the funding investigations, and the glossary.