JAMA Netw Open

Cannabis legalization linked to increased schizophrenia diagnoses

February 6, 2025

Study details: This cohort study examined 13,588,681 individuals from January 1, 2006, to December 31, 2022, aged 14 to 65 in Ontario, Canada, to assess changes in the incidence of schizophrenia diagnoses associated with cannabis use disorder (CUD) following cannabis legalization.

Results: The proportion of new schizophrenia cases linked to CUD nearly tripled during the period of substantial cannabis policy liberalization. Schizophrenia developed in 91,106 individuals (0.7%): 0.6% in the general population without CUD and 8.9% with CUD. The population-attributable risk fraction for CUD-associated schizophrenia rose from 3.7% pre-legalization to 10.3% post-legalization.

Clinical impact: These findings highlight the importance of monitoring and researching the long-term effects of cannabis policy changes on psychotic disorders. The potential link between CUD and schizophrenia, particularly in areas with more liberal cannabis laws, warrants further investigation.

Source:

Myran DT, et al. (2025, February 3). JAMA Netw Open. Changes in Incident Schizophrenia Diagnoses Associated With Cannabis Use Disorder After Cannabis Legalization. https://pubmed.ncbi.nlm.nih.gov/39903464/