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TOPLINE
Cannabis use was associated with a psychosis onset 2.5 years earlier on average compared with nonusers, a meta-analysis showed.
METHODOLOGY
- The meta-analysis included 181 samples from 149 cohort and case-control studies published until April 2025, searched using three databases.
- The included studies examined the association between cannabis use and age at onset (AAO) of psychosis and included 18,272 cannabis users and 52,801 nonusers.
- Subgroup analysis included stratification by sex, sample mean onset age (younger than 20 years [adolescent-onset], 20 to < 25 years, 25 to < 30 years, and 30 years or older) cannabis use pattern (heavy or continued vs light or discontinued), and country income status.
TAKEAWAY
- In the pooled sample analysis, cannabis users experienced psychosis onset 2.5 years earlier on average than nonusers (standardized mean difference [SMD], −0.365; P < .001).
- No significant difference was seen in adolescent-onset psychosis but cannabis users in the subgroups 20 to < 25 years, 25 to < 30 years, and 30 years or older had an earlier mean AAO by 1.6 years, 4.43 years, and 6.3 years respectively (all P < .001).
- Older sample mean onset age was associated with a stronger negative effect size, indicating earlier psychosis onset in cannabis users compared with nonusers (P < .0001).
- An increased proportion of men in the cannabis users group compared with the nonusers group was associated with a stronger negative effect size (P = .0015).
IN PRACTICE
“If cannabis use does causally contribute to earlier psychosis onset, especially if this effect extends beyond adolescence across the lifespan, the potential impact on population mental health would warrant clear and balanced public health warnings about possible psychiatric risks, including psychosis,” the investigators wrote.
SOURCE
The study was led by Carly Stevens, University of New South Wales, Sydney, Australia. It was published online on August 18 in Biological Psychiatry.
LIMITATIONS
The study was limited by residual heterogeneity and a limited number of studies in subgroup analysis based on cannabis exposure and sex.
DISCLOSURES
Funding information was not provided for the study. The investigators reported no potential conflicts of interest.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
