Does cannabis cause psychosis? What the EU-GEI study really found
- Claim
- CANNABIS CAUSES PSYCHOSIS?
- Catch
- OBSERVATIONAL ONLY
- Verdict
- A CLUE, NOT A VERDICT
Headlines claim cannabis causes psychosis. The EU-GEI multicentre case-control study, published in Lancet Psychiatry in 2019, compared 901 people with first-episode psychosis against 1,237 population controls across 11 sites in Europe and Brazil. Daily cannabis use was associated with about three times higher odds of psychotic disorder versus never-users (adjusted odds ratio 3.2, 95% CI 2.2-4.1). Daily use of high-potency cannabis (THC 10% or more) was associated with nearly five times the odds (OR 4.8, 95% CI 2.5-6.3). The authors estimated that, assuming causality, removing high-potency cannabis could prevent 12.2% of first-episode psychosis cases across the sites - 30.3% in London and 50.3% in Amsterdam.
The catch: this is an observational study, so it shows a link, not proof that cannabis causes psychosis. Psychosis remains rare, and most daily cannabis users never develop it. Not medical advice - talk to a doctor about cannabis use and mental health.
SOURCES
- Di Forti M, Quattrone D, Freeman TP, et al. "The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study." Lancet Psychiatry. 2019 May;6(5):427-436. DOI: 10.1016/S2215-0366(19)30048-3. PMID: 30902669. PMCID: PMC7646282.
For information only, not medical advice. Talk to a qualified health professional before changing your diet, supplements or treatment.
