New study on adolescent use of cannabis finds high risk of psychotic disorders
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- Study links adolescent cannabis use to double the risk of psychotic and bipolar disorders.
- Study of 463,000 teens in Northern California tracked diagnoses through age 26.
- Public health experts urge limits on THC potency and youth exposure to reduce harm.
A study on high THC levels in cannabis has concluded that adolescents using marijuana face a high risk of developing psychotic disorders by the time they are young adults.
The study published in JAMA Health Forum last week found that adolescents who use cannabis have double the risk of psychotic and bipolar disorders and a significantly high risk of suffering from depression and anxiety disorders.
The research followed 463,000 adolescents in Northern California, ages 13 to 17, until they were 26. It involved researchers from Kaiser Permanente, the University of California at San Francisco, the University of Southern California and the Public Health Institute’s Getting it Right from the Start project.
“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,” Lynn Silver, program director of Getting it Right, said in a news release.
Silver said a public health response is needed to reduce the potency of cannabis, limit youth exposure and treat adolescent cannabis use “as a serious health issue, not a benign behavior.”
In 2024, the California Department of Public Health convened an independent committee of scientists and medical experts, which recommended stronger limits on the potency of cannabis products and more rigorous regulation. But the recommendations have not been implemented.
The state report noted that average levels of the psychoactive ingredient in cannabis, tetrahydrocannabinol (THC), are more than 20% — five to 10 times higher than levels in the 1970s. After recreational marijuana was legalized for California adults in 2016, the industry produced concentrates up to 99% THC for vaping liquids.
“This (JAMA) study adds to the growing body of evidence that cannabis use during adolescence could have potentially detrimental, long-term health effects,” said Kelly Young-Wolff, lead author of the study and senior research scientist at the Kaiser Permanente Division of Research. “It’s imperative that parents and their children have accurate, trusted, and evidence-based information about the risks of adolescent cannabis use.”
The research looked at electronic records of pediatric visits between 2016 and 2023. The analysis found records of psychiatric diagnoses an average of 1.7 to 2.3 years after cannabis use began. Young patients who self-reported cannabis use in the past year (5.7 percent of the total) were twice as likely to be later diagnosed with psychotic or bipolar disorders, 34% more likely to be later diagnosed with depression and 24% more likely to develop anxiety disorders, Kaiser’s research division said.
Kaiser Permanente universally screens teenage patients and pregnant women for information about cannabis use, Silver said. The association between cannabis use and depression and anxiety was weaker for young people who began using at an older age.
The theory is that high-potency cannabis adversely affects the brains of adolescents, which are not fully developed until age 26. The legal age for purchasing permitted cannabis products in California is 21.
The national Monitoring the Future study has charted an increase in cannabis use among students in higher grade levels, growing from 8% among eighth-graders to 26% among high school seniors. More than 10% of teenagers in the United States, ages 12 to 17, had used marijuana in the past year, according to the 2024 National Survey on Drug Use and Health.
The Getting it Right from the Start project contends that cannabis legalization has mainly created a legal profit-making system for cannabis, rather than putting guardrails in place to protect public health and advance social equity.
The Public Health Institute noted that teenage cannabis use is more common among young people who are in the Medi-Cal program and those living in disadvantaged neighborhoods.
The state’s committee of experts that considered high-potency cannabis recommended policies that would reduce adverse health impacts by discouraging products with high THC levels and incentivizing retail products with less THC.
The committee’s report, citing more than 100 scientific studies and government reports, said serious adverse effects of high-potency cannabis included onset or worsening of psychosis and schizophrenia, increased risk of car crashes, higher risk of other mental disorders, cardiovascular disease, fertility problems for men and women, and respiratory disease if combined with tobacco smoking.
Pregnant women who use cannabis face a moderate increase in risk of adverse neonatal outcomes, lower birth weight and premature birth, the state report said.
The committee’s priority was to recommend policies to protect young people, pregnant woman and people with a history of mental health or substance use disorders.
Silver said she wasn’t aware of any proposed legislation this year to reduce the THC level in legal cannabis. A bill in Minnesota proposes to limit THC to 15% for cannabis buds and 30% for concentrates.
This story was originally published February 23, 2026 at 5:12 PM.
