Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational studies
PubMed 26884547 · doi:10.1093/schbul/sbw003
What was done
The authors conducted a systematic review and random-effects meta-analysis to assess the relationship between cannabis consumption level prior to onset and subsequent risk of psychosis. Electronic databases and bibliographies were searched for studies reporting cannabis dose criteria (frequency or amount) and psychosis-related outcomes. Individual data points were reconstructed from published summary statistics using a simulation method to model risk across use levels.
What was found
From 571 identified references, 18 studies met systematic review criteria and 10 studies (66,816 total individuals) were included in the meta-analysis. Higher levels of cannabis use were associated with increased psychosis risk across all included studies. A logistic regression model demonstrated an odds ratio of 3.90 (95% CI, 2.84 to 5.34) for schizophrenia and related psychotic outcomes when comparing the heaviest cannabis users to nonusers, confirming a dose-response gradient.
Why it matters
This review quantifies the dose-dependent association between cannabis consumption and psychotic outcomes across a large pooled population, providing robust evidence to guide clinical risk communication and targeted public health harm-reduction strategies.
Limits
The underlying observational studies cannot definitively establish causality due to potential residual confounding, genetic predisposition, or reverse causation. Reconstructing individual data points via simulation from published summary metrics may introduce modeling error, and definitions of heavy cannabis use varied across the primary studies.
Cited by
- supports Cannabis use, whether high-potency or low-potency, can trigger persistent psychotic episodes from which individuals do not recover, as supported by scientific data.