Marijuana is linked to worse mental health outcomes, including a higher risk of psychosis. A large cohort study published in JAMA Health Forum in 2026 found that past-year marijuana (cannabis) use during adolescence is associated with increased risk of developing psychotic disorders, bipolar disorder, depressive disorders, and anxiety disorders by young adulthood. This FAQ will review the information of the study and provide an interpretation of the data incorporating observations of staff across Pathway’s three locations.
Study Details
The study included 463,396 adolescents aged 13 to 17 years from Kaiser Permanente Northern California, with data collected from 2016 to 2023 and follow-up through age 25 or the end of 2023. Participants self-reported past-year cannabis use during routine screenings. Researchers tracked new (incident) clinician-diagnosed psychiatric disorders using electronic health records. Models adjusted for sex, race and ethnicity, neighborhood deprivation, insurance type, time-varying alcohol and other substance use, and were clustered by family. Associations held after further adjustments for prior psychiatric conditions and when excluding baseline cases.
This study confirms what our programs across our three locations have observed as well. Since the introduction of higher potency marijuana, there has been an increase in all psychiatric disorders described above.
Key Findings on Risks
Past-year cannabis use was associated with the following adjusted hazard ratios (AHR) for incident disorders:
- Psychotic disorders: AHR 2.19 (95% CI 1.97-2.42)
- Bipolar disorder: AHR 2.01 (95% CI 1.82-2.22)
- Depressive disorders: AHR 1.34 (95% CI 1.30-1.39)
- Anxiety disorders: AHR 1.24 (95% CI 1.21-1.28)
The strongest associations appeared for psychotic and bipolar disorders (approximately double the risk). For depressive and anxiety disorders, associations were weaker and decreased with age, becoming nonsignificant after age 20 in some models. Cannabis use preceded diagnoses by an average of 1.7 to 2.3 years.
Interpretation
An important factor to acknowledge is the greater implication stepping back from the specific data. Put most simply, any marijuana use over the last year increases the chances of worsening a teenager’s mental health. Most prior studies have focused on participants with severe cannabis use disorder. This study’s strength lies in its simple measure: adolescents were asked only whether they had used marijuana at all in the past year. Even with this broad definition that includes limited or occasional use, the adjusted risk nearly doubled for psychotic disorders and bipolar disorder.
Marijuana use in any capacity creates the potential to worsen, if not create in some cases, mental health diagnoses that could stick with a young person the rest of their lives.
Additional Notes
Associations remained significant (though slightly attenuated) after accounting for prior mental health conditions. The study was observational and shows association, not definitive causation. It was conducted in a region with legal cannabis access. Adolescent brain development may contribute to heightened vulnerability during this period.
Implications for Substance Abuse Programs
These findings support screening adolescents for cannabis use and providing education on potential mental health risks. Early intervention can help address substance use patterns before long-term issues emerge.
Source
Full study: https://jamanetwork.com/journals/jama-health-forum/fullarticle/2845356
For screening, support, or treatment related to cannabis use, contact our program.
