Teenagers who use cannabis may be more likely to develop serious mental illness by young adulthood, according to a major new study published in . JAMA Health Forum.
Researchers followed 463,396 adolescents between the ages of 13 and 17 to 26. Teens who reported using cannabis within the previous year were found to have a significantly higher risk of developing psychotic disorders, bipolar disorder, depression, and anxiety disorders later in life. Among adolescents who used cannabis, the risk of both psychotic disorders and bipolar disorder approximately doubled.
The study was conducted by researchers at 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 through a grant (R01DA0531920).
Cannabis use often occurred years before diagnosis
The study was based on electronic health record data collected during routine pediatric visits from 2016 to 2023. On average, cannabis use was reported 1.7 to 2.3 years before a mental illness diagnosis.
Because this study followed participants over time, the results provide strong evidence that cannabis exposure during adolescence may contribute to the later development of mental illness.
“As cannabis becomes more potent and more aggressively marketed, this study shows that adolescent cannabis use is associated with twice the risk of developing psychotic disorder and bipolar disorder, two of the most serious mental health conditions,” said study co-author Lynn Silver, M.D., program director of Getting it Right from the Start, a program at the Institute of Public Health. “Evidence increasingly points to the need for an urgent public health response that reduces product potency, prioritizes prevention, limits youth contact and marketing, and treats youth cannabis use as a serious health problem rather than a benign behavior.”
Cannabis use remains common among teens
Cannabis remains the most commonly used illicit drug among adolescents in the United States. According to data from the Monitoring the Future survey, usage rates steadily increase with age, from about 8% in 8th grade to 26% in 12th grade.
The 2024 National Survey on Drug Use and Health found that more than 10% of U.S. teens ages 12 to 17 reported using marijuana in the previous year.
At the same time, cannabis products are becoming much more potent. The average THC level in California cannabis flower is now over 20%, significantly higher than it has been in decades. Some cannabis concentrates contain more than 95% THC.
Risks beyond heavy cannabis use
Much of the early research focused primarily on heavy cannabis use or cannabis use disorder. This study took a broader approach, examining self-reported cannabis use in the past year. This information is obtained from universal screening performed as part of routine pediatric care.
“Even after accounting for prior mental health conditions and other drug use, adolescents who reported marijuana use had a significantly higher risk of developing mental illness, particularly psychotic disorder and bipolar disorder,” said Kelly Young Wolf, Ph.D., the study’s lead author and senior research scientist in the Kaiser Permanente Research Division. “This study adds to the growing body of evidence that adolescent cannabis use can have potentially harmful long-term health effects. It is essential that parents and children have accurate, reliable, evidence-based information about the risks of adolescent cannabis use.”
Concerns about mental health disparities
Researchers also found that cannabis use was more common among youth enrolled in Medicaid and among youth living in socioeconomically disadvantaged areas.
According to the authors, these findings raise concerns that the continued expansion of cannabis commercialization may exacerbate existing disparities in mental health outcomes.
