Does Early Cannabis Use Lead to Psychosis?
Studies have suggested an association between cannabis use and psychosis-related outcomes. In this sibling-pair analysis of an Australian birth cohort, researchers interviewed 3801 young adults (53% of the original cohort) to assess age-of-onset of cannabis use as well as nonaffective psychosis, hallucinations, and Peters et al. Delusions Inventory (PDI) score at 21-year follow-up. The sample included 228 sibling pairs.
- Those with 6 or more years since initiation of cannabis had an increased risk of nonaffective psychosis (adjusted odds ratio [AOR], 2.2), scoring in the highest quartile on the PDI (AOR, 4.2), and hallucinations (AOR, 2.8).
- Within the sibling pairs, there was a modest association between years since first cannabis use and PDI score.
- Notably, participants who reported hallucinations at the 14-year follow-up were more likely than those who didn’t to have longer times since first cannabis use and to use cannabis more frequently at the 21-year follow-up.