Teens who utilize cannabis are twice as likely to develop psychosis or bipolar disorder by early adulthood, according to a large-scale study published Monday in JAMA Health Forum. The research, which tracked nearly half a million adolescents over a decade, also found increased risks of depression and anxiety among those who used cannabis during their teenage years.
The longitudinal study, conducted by researchers analyzing data from the Kaiser Permanente Health System in Northern California, followed 463,396 adolescents aged 13 to 17 through age 26. Researchers examined annual screenings for substance use and mental health diagnoses recorded in patient health records. Crucially, the study excluded adolescents who already exhibited symptoms of mental illness prior to cannabis use, focusing instead on identifying new diagnoses following cannabis exposure.
The findings revealed that any past-year cannabis use during adolescence was associated with a significantly increased risk of developing clinically diagnosed psychotic, bipolar, depressive, and anxiety disorders by age 26. The most substantial increases in risk were observed for psychotic and bipolar disorders, with adolescent cannabis use linked to more than double the risk of both conditions.
“This is very, very, very worrying,” said psychiatrist Dr. Ryan Sultan of Columbia University, who was not involved in the study. His comment reflects growing concern among mental health professionals regarding the potential long-term effects of adolescent cannabis use.
The study’s design strengthens its conclusions, according to researchers. The large sample size, diversity of the participant pool, and use of real-world health data – rather than self-reported symptoms or data focused solely on cannabis use disorder – distinguish it from much of the previous research on this topic. The Public Health Institute highlighted the study’s significance, noting it moves beyond smaller samples and focuses on physician-diagnosed mental illness.
Researchers found that psychiatric diagnoses typically emerged within two years of initial cannabis use, regardless of the teen’s prior mental health history or socioeconomic background. This timeframe is particularly concerning given the increasing potency of modern cannabis products, with some flower exceeding 20% THC and concentrates reaching 95% THC levels.
The study indicated that the associations with depressive and anxiety disorders were strongest when cannabis use began during earlier adolescence, a critical period for brain development. This suggests that earlier exposure may have more profound and lasting effects on mental health.
The findings add to a growing body of evidence suggesting that cannabis use in adolescence is a risk factor for developing psychiatric conditions. Researchers emphasize that psychotic and bipolar disorders are life-altering conditions with long-term consequences for health, education, employment, and family stability.
As of Monday, February 23, 2026, Kaiser Permanente has not issued a statement regarding potential changes to its adolescent substance use screening protocols in light of the study’s findings.
