Adolescents who use cannabis may be more likely to develop serious psychiatric illnesses in adulthood, according to a major new study published in JAMA Health Forum.
Researchers tracked 463,396 adolescents between the ages of 13 and 17 and up to age 26. They found that adolescents who reported using cannabis in the past year faced significantly increased risks of later developing psychotic disorders, bipolar disorder, depression and anxiety. The risk of psychotic and bipolar disorders approximately doubled among adolescents who used cannabis.
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 came from the National Institute on Drug Abuse through a grant (R01DA0531920).
Cannabis use often occurred years before diagnosis
The research was based on data from electronic medical records collected during routine pediatric visits between 2016 and 2023. On average, cannabis use was reported between 1.7 and 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 psychotic and bipolar disorders, two of the most serious mental health conditions,” said Lynn Silver, MD, director of the Getting it Right from the Start program, a program of the Institute for Public Health, and co-author of the study. “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 problem, not a benign behavior.”
Cannabis use remains common among adolescents
Cannabis remains the most commonly used illicit drug among adolescents in the United States. Data from the Monitoring the Future study shows that use increases steadily with age, rising from approximately 8% of eighth graders to 26% of twelfth graders.
The 2024 National Survey on Drug Use and Health found that more than 10% of American adolescents ages 12 to 17 reported using cannabis in the past year.
At the same time, cannabis products have become much stronger. Average THC levels in California cannabis flowers currently exceed 20%, considerably higher than in past decades. Some cannabis concentrates contain more than 95% THC.
Risks observed beyond excessive cannabis consumption
Many previous studies focused primarily on excessive cannabis use or cannabis use disorders. This study took a broader approach and examined any self-reported cannabis use over the past year. The data came from universal screening tests performed as part of routine pediatric care.
“Even after accounting for prior mental health conditions and other substance use, adolescents who reported using cannabis were at substantially increased 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 Kaiser Permanente’s Research Division. “This study adds to the growing body of evidence that cannabis use during adolescence could have potentially harmful long-term health effects. It is imperative that parents and their children have accurate, reliable, evidence-based information about the risks of cannabis use in adolescents.”
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 more socioeconomically disadvantaged neighborhoods.
According to the authors, these findings raise concerns that the continued expansion of cannabis marketing could worsen existing disparities in mental health outcomes.