Researchers tracked 463,396 adolescents between the ages of 13 and 17 through age 26. They found that teens who reported using cannabis within the previous year faced significantly higher risks of later developing psychotic disorders, bipolar disorder, depression, and anxiety. The risk of both psychotic and bipolar disorders was approximately 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 program, the University of California, San Francisco, and the University of Southern California. Funding came from the National Institute on Drug Abuse through grant (R01DA0531920).

Cannabis Use Often Came Years Before Diagnosis

The research relied on electronic health record data collected during routine pediatric visits from 2016 through 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, M.D., program director of the Getting it Right from the Start, a program 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, prioritizes prevention, limits youth exposure and marketing and treats adolescent cannabis use as a serious health issue, not a benign behavior."

Cannabis Use Remains Common Among Teens

Cannabis remains the most commonly used illicit drug among adolescents in the United States. Data from the Monitoring the Future study show that use increases steadily with age, rising from about 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 between the ages of 12 and 17 reported using cannabis during the previous year.

At the same time, cannabis 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 Seen 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 pediatric 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, Ph.D., lead author of the study and senior research scientist at the Kaiser Permanente Division of Research. "This 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 the risks of adolescent cannabis use."

Concerns About Mental Health Disparities

The researchers also found that cannabis use was more common among adolescents enrolled in Medicaid and among those living in neighborhoods with greater socioeconomic disadvantage.

According to the authors, these findings raise concerns that the continued expansion of cannabis commercialization could worsen existing disparities in mental health outcomes.