Study Examines Link Between Cannabis and Mental Illness

Large U.S. study published in JAMA Health Forum finds adolescents who used cannabis faced “significantly higher” risk of psychotic and bipolar disorders by young adulthood

Teenagers who used cannabis were at a significantly higher risk of developing serious psychiatric disorders by their mid-20s, according to a major American study tracking nearly half a million adolescents.

The research, published in JAMA Health Forum, followed 463,396 adolescents between the ages of 13 and 17 through age 26. Scientists found that cannabis use in the previous 12 months during adolescence was associated with roughly double the risk of developing psychotic and bipolar disorders.

In addition, teen cannabis use was linked to a significantly increased risk of depression and anxiety disorders.

Researchers said cannabis use typically preceded psychiatric diagnoses by an average of 1.7 to 2.3 years, strengthening evidence that adolescent exposure may be a contributing risk factor rather than a consequence of emerging mental illness.

Researchers say findings strengthen case for public health action as cannabis potency rises and youth use remains widespread across the United States

The study analyzed electronic health record data collected during routine pediatric visits between 2016 and 2023. Unlike many earlier studies that focused primarily on heavy users, the research examined any self-reported cannabis use identified through universal screening in standard pediatric care.

The team found cannabis use was more common among teenagers living in more socio-economically deprived neighborhoods, highlighting disparities in exposure and potential health impacts.

Study co-author Dr. Lynn Silver, of the Public Health Institute in Oakland, California, said the findings are especially concerning as cannabis products grow stronger and more widely marketed.

“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.

She added that the evidence points to the need for an urgent public health response focused on reducing product potency, limiting youth exposure and marketing, and treating adolescent cannabis use as a serious health issue.

Cannabis remains the most commonly used illicit drug in the United States. According to the 2024 National Survey on Drug Use and Health, more than 10% of Americans ages 12 to 17 reported using cannabis within the previous year.

Lead author Dr. Kelly Young-Wolff, of the Kaiser Permanente Division of Research, said the association held even after researchers accounted for prior mental health conditions and other substance use.

“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,” she said.

Young-Wolff added that the findings underscore the importance of ensuring that families have access to accurate, evidence-based information.

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