A major study of nearly half a million adolescent cannabis users found they may face a substantially greater risk of developing serious mental health conditions, including psychotic and bipolar disorders, according to the findings published in JAMA Health Forum.
The researchers found cannabis use often preceded these diagnoses by nearly two years, strengthening concerns about its long-term effects on developing brains.
They had tracked 463 396 adolescents between 13 and 17 until the age of 26. Those who reported using cannabis within the previous year faced significantly higher risks of later developing psychotic disorders, bipolar disorder, depression and anxiety, while the risk of both psychotic and bipolar disorders doubled among adolescents who used cannabis.
The study was carried out by researchers from Kaiser Permanente, the Public Health Institute’s Getting it Right from the Start programme, the University of California-San Francisco, and the University of Southern California. Funding came from the National Institute on Drug Abuse.
Use years before diagnosis
The research relied on electronic health record data collected during routine paediatric visits from 2016 until 2023. On average, cannabis use was reported 1.7 to 2.3 years before a psychiatric disorder was diagnosed.
Because the study followed participants over time, the findings provide stronger evidence that cannabis exposure during adolescence may contribute to the later development of mental illness.
“As cannabis becomes more potent and aggressively marketed, this study indicates that adolescent cannabis use is associated with double the risk of incident psychotic and bipolar disorders, two of the most serious mental health conditions,” said Lynn Silver, MD, programme director of the Getting it Right from the Start, a programme of the Public Health Institute, and a study co-author.
"The evidence increasingly points to the need for an urgent public health response – one that reduces product potency, prioritises prevention, limits youth exposure and marketing, and treats adolescent cannabis use as a serious health issue, not a benign behaviour.”
Common with teens
Cannabis remains the most commonly used illicit drug among adolescents in the United States. The 2024 National Survey on Drug Use and Health found that more than 10% of American teens aged 12 to 17 reported using cannabis during the previous year.
At the same time, the products have become much stronger. Average THC levels in California cannabis flower now exceed 20%, considerably higher than in past decades. Some cannabis concentrates contain more than 95% THC.
Risks beyond heavy cannabis use
Many earlier studies focused primarily on heavy cannabis use or cannabis use disorder. This study took a broader approach, examining any self-reported cannabis use within the past year. The information came from universal screening conducted as part of routine paediatric care.
"Even after accounting for prior mental health conditions and other substance use, adolescents who reported cannabis use had a substantially higher risk of developing psychiatric disorders – particularly psychotic and bipolar disorders,” said Kelly Young-Wolff, PhD, lead author of the study and senior research scientist at the Kaiser Permanente Division of Research.
“The study adds to the growing body of evidence that cannabis use during adolescence could have potentially detrimental, long-term health effects. It’s imperative that parents and their children have accurate, trusted, and evidence-based information about these risks.”
Cannabis use was more common in neighbourhoods with greater socioeconomic disadvantage and the study authors said the findings raise concerns that the continued expansion of cannabis commercialisation could worsen existing disparities in mental health outcomes.
Study details
Adolescent cannabis use and risk of psychotic, bipolar, depressive, and anxiety disorders.
Kelly Young-Wolff, Catherine Cortez, Stacey Alexeeff, et al.
Published in JAMA Health Forum on 20 February 2026
Key Points
Question Is adolescent cannabis use associated with an increased risk of developing psychiatric disorders by young adulthood?
Findings In this cohort study of 463 396 adolescents aged 13 to 17 years who were universally screened for cannabis use, past-year cannabis use was associated with a significantly increased risk of incident psychotic, bipolar, depressive, and anxiety disorders by 26.
Meaning This study found that adolescent cannabis use is associated with increased risk of psychiatric disorders in adolescence and young adulthood, highlighting the importance of early prevention efforts, effective public health messaging, and policy development to limit youth exposure as cannabis legalisation expands.
Abstract
Importance
As cannabis becomes more accessible and socially accepted, concerns have grown about its potential implications for adolescent mental health. While prior research has linked adolescent cannabis use to psychiatric symptoms, few large, population-based, longitudinal studies have examined associations with clinically diagnosed psychiatric disorders.
Objective
To evaluate whether adolescent cannabis use is associated with an increased risk of incident psychotic, bipolar, depressive, and anxiety disorders during adolescence and young adulthood.
Design, Setting, and Participants
This cohort study included adolescents aged 13 to 17 screened for past-year cannabis use at Kaiser Permanente Northern California from 2016 to 2023. Adolescents were followed up until age 25 or until December 31, 2023. Data were analysed from February 21, 2024, to August 27, 2025.
Exposure
Time-varying self-reported past-year cannabis use based on universal, confidential screening during standard paediatric care.
Main Outcomes and Measures
Incident clinician-diagnosed psychotic, bipolar, depressive, and anxiety disorders, which were identified through electronic health records using International Classification of Disease codes. Cox proportional hazards regression models were used to measure the strength of associations between adolescent cannabis use and incident psychiatric diagnoses, with adjustments for sex, race and ethnicity, neighbourhood deprivation index, insurance type, and time-varying alcohol and other substance use.
Results
Of 463 396 adolescents (234 114 males [50.5%]; mean [SD] age, 14.5 [1.3] years) included in the sample, 136 708 were Hispanic individuals (29.5%), 93 737 were non-Hispanic Asian individuals (20.2%), 35 346 were non-Hispanic Black individuals (7.6%), 153 102 were non-Hispanic White individuals (33.0%), and 18 795 individuals were multiracial or of other races or ethnicities (4.1%). At baseline, 26 345 adolescents (5.7%) self-reported past-year cannabis use. Past-year cannabis use was associated with an increased risk of incident psychotic (adjusted hazard ratio [AHR], 2.19; 95% CI, 1.97-2.42), bipolar (AHR, 2.01; 95% CI, 1.82-2.22), depressive (AHR, 1.34; 95% CI, 1.30-1.39), and anxiety disorders (AHR, 1.24; 95% CI, 1.21-1.28). The strength of the associations between cannabis use and incident depressive and anxiety disorders decreased as adolescents aged. This pattern was similar but slightly attenuated after additional adjustment for past psychiatric conditions (psychotic disorder: AHR, 1.92; 95% CI, 1.73-2.13; bipolar disorder: AHR, 1.73; 95% CI, 1.57-1.90; depressive disorder: AHR, 1.33; 95% CI, 1.29-1.38; anxiety disorder: AHR, 1.19; 95% CI, 1.16-1.23).
Conclusions and Relevance
This cohort study found that adolescent cannabis use was associated with increased risk of incident psychiatric disorders, particularly psychotic and bipolar disorders. These results could inform the development of clinical and educational interventions for parents, adolescents, and clinicians, as well as protective policies to prevent or delay adolescent cannabis use in the context of expanding cannabis legalisation.
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