FRIDAY, Aug. 21, 2026 (HealthDay News) -- Cannabis users may have an earlier age at onset (AAO) of psychosis than nonusers, with larger differences accumulating with age, according to a review published online Aug. 18 in Biological Psychiatry.
Carly Stevens, M.D., from the University of New South Wales in Sydney, and colleagues conducted a systematic literature review and meta-analysis to update evidence on the association between cannabis use and AAO of psychosis.
Based on 149 studies (18,272 cannabis users and 52,801 nonusers), the researchers found that cannabis use was associated with earlier AAO by a mean of 2.5 years earlier. In a subgroup analysis, among those younger than 20 years old, there was no difference in AAO of psychosis between cannabis users and nonusers; however, there were age-related differences observed with increasing age. AAO in cannabis users aged 20 to <25, 25 to <30, and 30 and older was earlier by 1.60, 4.43, and 6.30 years, respectively. The sample mean onset age was a strong and statistically independent moderator of earlier AAO effect size in multiple meta-regression.
"We've tended to focus on the dangers of using cannabis in adolescence, when the brain is still developing, but the risk doesn't disappear once you're in your 20s," coauthor Matthew Large, M.B.B.S., also from the University of New South Wales, said in a statement. "What we're seeing suggests a cumulative effect, where harm builds up over time, a bit like alcohol or nicotine."
