Large Kaiser Study Links Adolescent Cannabis Use to Higher Rates of Psychiatric Disorders

Longitudinal cohort study of adolescents ages 13–17 screened at Kaiser Permanente Northern California, 2016–2023, with follow-up through age 25 or December 31, 2023. Time-varying self-reported past-year cannabis use from universal confidential screening. Outcomes: clinician-diagnosed psychotic, bipolar, depressive, and anxiety disorders from electronic health records. Cox proportional hazards regression models.

Published in JAMA Health Forum, this is one of the largest and most methodologically rigorous studies linking adolescent cannabis use to clinician-diagnosed psychiatric disorders. The universal screening design captures a more representative population than studies relying on treatment-seeking or survey samples, and the electronic health record outcomes are more reliable than self-reported symptoms.

This study provides the population-level epidemiological anchor for the psychiatric risk evidence scattered across this database. The psychosis meta-analysis (RTHC-00251) found ~34% of cannabis-induced psychosis cases convert to schizophrenia. The placental gene study (RTHC-00254) found molecular mechanisms linking prenatal THC to schizophrenia. The antipsychotic dosing study (RTHC-00261) addressed treatment after cannabis psychosis. This Kaiser study provides the foundational longitudinal data showing that adolescent cannabis use precedes clinically diagnosed psychiatric disorders at elevated rates across the full spectrum of major mental illness.

Observational study — cannot prove cannabis caused the psychiatric disorders. Adolescents who use cannabis may differ from non-users in unmeasured ways (genetics, trauma history, family psychiatric history) that independently increase psychiatric risk. Cannabis use was self-reported during screening, though the confidential clinical setting may improve accuracy. Kaiser members may not represent all adolescents.