Adolescent cannabis use linked to higher risk of psychiatric illness

Past-year cannabis use in adolescence was linked to higher risk of psychotic, bipolar, depressive and anxiety disorders by young adulthood in a Kaiser Permanente Northern California cohort of 463,396 patients ages 13 to 17. The study, published Feb. 20, 2026 in JAMA Health Forum, followed teens screened during routine pediatric visits from 2016 to 2023 and found the strongest signal for psychotic and bipolar disorders, where risk was about doubled.

The researchers, including Kelly C. Young-Wolff, Catherine A. Cortez, Stacey E. Alexeeff and colleagues from Kaiser Permanente Northern California, the Kaiser Permanente Division of Research, the Public Health Institute’s Getting it Right from the Start program, the University of California, San Francisco and the University of Southern California, used universal, confidential screening built into standard care. At baseline, the mean age was 14.5 years, and 26,345 adolescents, or 5.7%, reported cannabis use in the previous year.

The analysis held even after adjusting for sex, race and ethnicity, neighborhood deprivation index, insurance type, and time-varying alcohol and other substance use. Researchers said cannabis use appeared 1.7 to 2.3 years before psychiatric diagnoses, a timing pattern that supports concern about exposure coming first, although Kaiser Permanente said the study could not definitively determine causation because some teens may have used cannabis to cope with emerging symptoms.

The association with depression and anxiety was weaker than the link with psychotic and bipolar disorders, but it still mattered: the study found adolescents who used cannabis were 34% more likely to be diagnosed with depression and 24% more likely to be diagnosed with anxiety disorders. Lynn Silver said the findings pointed to an urgent public health response as cannabis becomes more potent and more aggressively marketed, including lower product potency, tighter limits on youth exposure and advertising, and treating adolescent cannabis use as a serious health issue rather than a harmless behavior.

The results land in the middle of a national debate over legalization, youth access and product strength, and they deepen the gap between reassuring public messaging and the psychiatric risk monitoring that routine adolescent care would need to catch problems early. The concern is not limited to one study. A 2023 JAMA Psychiatry cohort of 6,651,765 people in Denmark found cannabis use disorder was associated with higher risk of unipolar depression and bipolar disorder, reinforcing a pattern that extends beyond short-term impairment and into later mental health.