Studies show that more than one in every four high school seniors (26%) have used marijuana in the past year, but almost half of 12th graders have tried it at least once in their lifetimes. Most people first use marijuana during their adolescent or young adult years, when their brains are still developing. Unfortunately, what many teenagers (and parents) don’t realize is that use of marijuana during this time can come with significant risks.
We’ve discussed these dangers before—marijuana use at a young age can contribute to cognitive issues, stir up problems at school, and give way to future substance use disorders. It can also lead to the development and early onset of mental health issues, including psychosis.
However, new research has emerged on the risks of teen marijuana use—and the results are worrisome. A massive, longitudinal study published in February 2026 found that cannabis use during the teenage years significantly increased a person’s risk of developing psychotic, depressive, anxiety, and bipolar disorders in early adulthood.
Key Findings of the New Study:
The JAMA-published study analyzed health data from more than 460,000 teenagers, who previously had no history of mental illness, and followed them from age 13 to 26 years old. The results were clear as day: The teens who reported cannabis use were at a higher risk of being diagnosed with several mental health conditions within a few years, compared to teens who didn’t use marijuana at all.
Specifically, the research found:
- Teenagers who used marijuana between the ages of 13 and 17 were twice as likely to develop psychotic disorders or bipolar disorder.
- These disorders were typically diagnosed about two years after the first report of marijuana use, with all reported diagnoses occurring by 26 years old.
Researchers found that the risk of depression and anxiety disorders also increased among early cannabis users, but at a fraction of the rate of these more serious and complex conditions. While the risk of psychotic disorders like schizophrenia, and bipolar disorder, increased 100%, the risk of depression and anxiety increased between 25% and 35% among teen marijuana users.
What Does This All Mean?
The adolescent brain is extremely malleable and vulnerable, and the new research only underlines this fact. Dr. Lynn Silver, a researcher at the Public Health Institute and author of this study, explains: “The brain is still developing. The effects of cannabis on the receptors in the brain seem to have a significant impact on their neurological development and the risk for these mental health disorders.”
And the conditions stemming from cannabis use are quite serious. Psychotic disorders like schizophrenia are characterized by a disconnect from reality—with distorted thoughts, hallucinations, and delusions being common symptoms. Bipolar disorder, on the other hand, is marked by intense, alternating episodes of depression and mania. Both types of conditions are complex, scary, and disabling.
However, their development is not entirely surprising. Research has long understood the connection between marijuana and psychosis, with cannabis-induced psychosis and manic episodes previously reported as side effects of cannabis use. When these side effects occur, doctors will typically warn individuals not to use marijuana again, because continued use can make symptoms much worse. In fact, one study found that 75% of individuals who experienced cannabis-induced psychotic episodes went on to develop chronic psychotic disorders.
Dr. Ryan Sultan, a psychiatrist and researcher at Columbia University, explained this dynamic more in an NPR interview: “What we’re worried about [is if] you sort of get stuck in psychosis, it gets harder and harder to pull the person back. Psychosis and severe mood disorders, particularly bipolar disorder, are like seizures in your brain.” He describes these disorders as “neurotoxic” and associates them with a “more rapid deterioration” of the brain.
Marijuana, and specifically its active agent THC, can also cause a severe decline in brain function. Especially during critical periods of growth, it can disrupt the endocannabinoid system and cause long-term cognitive effects. THC, the study explains, “acts on cannabinoid 1 receptors, which are highly expressed in the adolescent brain, and may disrupt neurodevelopment and affect areas of the brain associated with motivation, emotional, and affective processing, especially with early onset of cannabis use.”
So, it’s no wonder why marijuana has such devastating effects when used in adolescence—a monumental, yet vulnerable period of brain development. It stunts maturation. It disrupts the brain’s natural process. It doubles psychosis and bipolar disorder risk. And these are just some of the risks.
Other Risks of Teen Marijuana Use
On top of the study’s findings, once again linking marijuana use to psychosis and other mental health conditions, we know marijuana carries other severe consequences when used at an early age.
Risks of teenage marijuana use also include:
- Addiction: SAMHSA reports that 1 in 6 teenagers who use marijuana will become addicted.
- Cognitive issues: Marijuana has been linked to difficulties in problem-solving, paying attention, retaining information, and learning new things, according to the CDC.
- Academic troubles: Teens who use marijuana are five times more likely to drop out of school. Studies have also connected early marijuana use with a decline in IQ.
These factors, combined with the significant risks of mental illness and psychosis, should make us all question the real safety of marijuana use. Yes, it’s a plant. Yes, it’s legal in some states (for adults). Yes, marijuana use is more normalized than ever. But does that make it risk-free? Absolutely not.
If you are a parent of a teenager, or a teen researching this topic, know that cannabis use can severely disrupt, inhibit, and stunt brain development during the adolescent years. It may be common to use marijuana, but the risks are not worth the reward. Especially for teens with family histories of mental health problems, who are using marijuana daily, or who are using high-potency THC, the risk of psychosis is even higher. Don’t take the chance.
If you are a frequent marijuana user and already dependent on the drug, know that it’s not too late to stop. You can take steps to protect yourself and your mind right now. Get the treatment you deserve. As a mental health and substance use treatment provider for teenagers, Turnbridge is here for you.
Contact us at 877-581-1793 today.