New research says that teens who use cannabis are more likely to face serious mental‑health problems later in life.
Scientists followed 463,396 young people from ages 13‑17 until they were 26. Those who said they had used cannabis in the past year were more likely to be diagnosed with psychosis, bipolar disorder, depression, or anxiety. The chance of psychosis and bipolar disorder was about twice as high for the users.
The study was done by teams from Kaiser Permanente, the Public Health Institute, the University of California‑San Francisco, and the University of Southern California. Funding came from the National Institute on Drug Abuse.
Health records from routine doctor visits between 2016 and 2023 were used. On average, teens reported using cannabis 1.7 to 2.3 years before a mental‑health diagnosis appeared.
Because the researchers watched the participants over time, the findings give strong clues that cannabis use in adolescence can help trigger later mental illness.
Cannabis Is Still Popular Among Teens
Weed remains the most common illegal drug for U.S. teenagers. Surveys show use rises with age – about 8% of eighth‑graders and 26% of seniors have tried it. A 2024 national survey found that more than 10% of 12‑17‑year‑olds used cannabis in the previous year.
Today’s cannabis is stronger. In California, the average THC level in flower often exceeds 20%, and some concentrates contain over 95% THC.
Not Only Heavy Users Are at Risk
Earlier studies focused on heavy use or cannabis‑use disorder. This new work looked at any self‑reported use in the past year, based on universal screening in pediatric care.
Unequal Impact
The researchers also noticed higher use among teens on Medicaid and those living in neighborhoods with greater economic hardship.