Large-Scale Study Finds Teen Cannabis Use Doubles the Risk of Serious Mental Illness

Teen Cannabis Use Linked to Doubled Risk of Severe Psychiatric Disorders

A sweeping new study involving nearly half a million adolescents has found that teenagers who use cannabis face significantly elevated risks of developing serious mental health conditions, including psychotic and bipolar disorders. The research, published in JAMA Health Forum, also revealed that cannabis use typically began almost two years before any psychiatric diagnosis was made — a timeline that raises serious concerns about the drug's impact on still-developing adolescent brains.

What the Research Found

Researchers tracked 463,396 young people between the ages of 13 and 17, following them through age 26. Among those who reported using cannabis in the prior year, the odds of later receiving a diagnosis of psychotic disorder or bipolar disorder were roughly twice as high compared to non-users. Elevated risks were also observed for depression and anxiety.

The study was a collaborative effort between Kaiser Permanente, the Public Health Institute's Getting it Right from the Start program, the University of California San Francisco, and the University of Southern California. Funding was provided by the National Institute on Drug Abuse.

Cannabis Use Preceded Diagnosis by Nearly Two Years

Data for the study was drawn from electronic health records gathered during routine pediatric appointments between 2016 and 2023. On average, adolescents reported cannabis use approximately 1.7 to 2.3 years before being diagnosed with a psychiatric condition. Because the study followed participants longitudinally rather than capturing a single point in time, the results offer a stronger foundation for understanding how cannabis exposure during the teenage years may contribute to the onset of mental illness later in life.

Expert Voices: An Urgent Public Health Matter

Lynn Silver, M.D., program director of Getting it Right from the Start and a co-author of the study, emphasized the seriousness of these findings in the context of today's increasingly potent cannabis market.

"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," Silver said. "The evidence increasingly points to the need for an urgent public health response — one that reduces product potency, prioritizes prevention, limits youth exposure and marketing, and treats adolescent cannabis use as a serious health issue, not a benign behavior."

Kelly Young-Wolff, Ph.D., lead author and senior research scientist at the Kaiser Permanente Division of Research, added that the elevated risks held up even after accounting for prior mental health diagnoses and other substance use.

"This study adds to the growing body of evidence that cannabis use during adolescence could have potentially detrimental, long-term health effects," Young-Wolff said. "It's imperative that parents and their children have accurate, trusted, and evidence-based information about the risks of adolescent cannabis use."

A Drug That's More Common — and More Potent — Than Ever

Cannabis remains the most widely used illicit substance among American teenagers. Data from the Monitoring the Future study shows usage climbing steadily with age — from around 8% of eighth graders to 26% of twelfth graders. The 2024 National Survey on Drug Use and Health found that more than 10% of U.S. teens aged 12 to 17 reported using cannabis within the previous year.

At the same time, today's cannabis products are far more powerful than those of previous generations. Average THC concentrations in California cannabis flower now surpass 20%, and certain cannabis concentrates have been found to contain more than 95% THC.

A Broader Lens on Cannabis Use

Unlike many earlier studies that focused narrowly on heavy users or those diagnosed with cannabis use disorder, this research cast a wider net — examining any self-reported cannabis use within the past year, captured through universal screening during standard pediatric care visits.

Mental Health Disparities a Growing Concern

The study also uncovered troubling patterns related to socioeconomic status. Cannabis use was found to be more prevalent among teens enrolled in Medicaid and those living in economically disadvantaged neighborhoods. The researchers warn that the ongoing commercialization and expansion of cannabis markets could deepen existing mental health disparities, disproportionately affecting already vulnerable youth populations.

These findings collectively make a compelling case for stronger public health policies targeting adolescent cannabis use — including tighter restrictions on marketing, greater investment in prevention programs, and increased regulation of product potency.