Researchers followed 463,396 American adolescents aged 13–17 into young adulthood to examine links between cannabis use and later psychiatric conditions. They found that teens reporting any cannabis use within the previous year faced significantly higher risks of developing psychotic disorders, bipolar disorder, depression, and anxiety by age 26.
The study, published in JAMA Health Forum, used health records collected during routine doctor visits between 2016 and 2023, making it one of the largest and most rigorous examinations of this question to date.
Risk of Psychosis and Bipolar Disorder Roughly Doubled
Adolescents who used cannabis were approximately twice as likely to develop psychotic disorders or bipolar disorder in young adulthood compared to non-users. These are among the most serious mental health conditions, often requiring long-term treatment. The study looked at self-reported cannabis use among any teenagers, not just heavy users, which broadens the relevance of findings beyond a small high-risk group.
Mental Illness Emerged Years After Cannabis Use
On average, psychiatric diagnoses appeared 1.7 to 2.3 years after cannabis use was first reported. This time gap strengthens the evidence that cannabis exposure may actually trigger mental illness, rather than simply being used by teens already struggling with their mental health. The researchers accounted for prior mental health conditions in their analysis, supporting this conclusion.
Today's Cannabis Is Far More Potent Than Before
Cannabis products have grown substantially stronger over recent decades. Average THC levels (the main psychoactive ingredient) in cannabis flower now exceed 20% in some markets, with concentrates reaching over 95%. More than 10% of US teens aged 12–17 report using cannabis annually, and use increases steadily from early to late teens. The combination of higher potency and wider availability may amplify risks for developing adolescents whose brains are still developing.
Reduce Cannabis Exposure During the Teen Years
- Understand that even occasional cannabis use in adolescence carries psychiatric risk; it is not a harmless behaviour during these critical developmental years.
- Be alert to changes in mood, social withdrawal, or unusual thinking patterns in your teenager, which may signal emerging mental health conditions.
- Know your teen's social circles and activities; parental awareness of substance use risk is a documented protective factor during adolescence.