Does cannabis use raise risk of psychotic and bipolar disorders?

They face a "significantly higher" risk of developing serious psychiatric problems by young adulthood, say scientists.

The American study, published in the journal JAMA Health Forum, followed 463,396 adolescents ages 13 to 17 through to the age 26.

The findings showed that using cannabis in the previous 12 months during adolescence was associated with double the risk of psychotic and bipolar disorders as well as significantly higher risk of depressive and anxiety issues.

The study also found that cannabis use was more common among teenagers living in more socio-economically deprived neighborhoods.

Researchers analyzed electronic health record data from routine pediatric visits between 2016 and 2023.

Cannabis use preceded psychiatric diagnoses by an average of 1.7 to 2.3 years.

The research team said that the study’s design strengthens evidence that adolescent cannabis exposure is a potential risk factor for developing mental illness.

Study co-author Dr. Lynn Silver said: “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."

Dr. Silver, of the Public Health Institute in Oakland, California, added: “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 is the most used illicit drug with more than 10% of all Americans aged 12 to 17 having used it within the last 12 months, according to the 2024 National Survey on Drug Use and Health.

And research shows cannabis is getting stronger.

Unlike many previous studies, the new research examined any self-reported cannabis use, with universal screening of teens during standard paediatric care, rather than focusing only on heavy users.

Lead author Dr. Kelly Young-Wolff said: “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.

“This study adds to the growing body of evidence that cannabis use during adolescence could have potentially detrimental, long-term health effects."

Dr. Young-Wolff, of the Kaiser Permanente Division of Research, added: "It’s imperative that parents and their children have accurate, trusted, and evidence-based information about the risks of adolescent cannabis use.”