Cannabis is often talked about as “natural” and therefore harmless. But for teens and young adults—whose brains are still developing—new research is adding urgency to a message families and clinicians have been sounding for years: earlier cannabis use may carry real mental health risk.

Cannabis Use and Mental Health

What a Large New Study Suggests About Teen Cannabis Use—and Why Earlier Use May Matter Most

A large longitudinal study published in JAMA Health Forum and highlighted by NPR followed hundreds of thousands of adolescents who did not have any mental health symptoms and tracked later mental health diagnoses into young adulthood. The findings add weight to concerns about teen cannabis use and serious psychiatric outcomes.

Higher Risk for Serious Mental Health Diagnoses

According to the study, teens who reported using cannabis in the past year had a higher risk of being diagnosed later with several mental health conditions compared with teens who did not report cannabis use.

Most notably, the article reports that teens who used cannabis had about twice the risk of developing:

• Bipolar disorder (alternating episodes of depression and mania)
• Psychotic disorders (including conditions such as schizophrenia that involve a break with reality)

It’s important to keep perspective: NPR notes that only a small fraction of the full sample—nearly 4,000 teens—were diagnosed with each of these two disorders. Even so, bipolar disorder and psychotic disorders are among the most serious and disabling mental illnesses, and the potential for preventable risk matters.

Depression and Anxiety Rates Also Higher

The study didn’t just focus on rare, severe conditions. There was also a higher risk for more common concerns as well:

• Depression increased by about a third
• Anxiety increased by about a quarter

And there’s a key nuance for parents and caregivers: the association between cannabis use and depression/anxiety was strongest for those teens who began using earlier—suggesting that younger adolescents may be more vulnerable.

Answering “Which Came First?”

One of the biggest challenges in cannabis-and-mental-health research is sorting out whether cannabis contributes to mental health symptoms—or whether teens with early symptoms are more likely to use cannabis.

Researchers addressed this by excluding adolescents who had symptoms of mental illness before using cannabis, then following participants forward in time. That design can’t prove causation on its own, but it strengthens the argument that cannabis use may play a contributing role for some young people.

Practical Takeaways

If you’re a parent of a teen or young adult, this research supports a few clear, prevention-oriented steps.

1) Treat “it’s just weed” as a myth—not a plan

Legalization and cultural normalization can make cannabis feel low-risk. But cannabis is far riskier than popular culture suggests, especially for adolescents.

2) Earlier use appears to carry higher vulnerability

The younger the brain, the more development is still underway. That’s why delaying first use matters. For adults who do not try cannabis until after they are 26, there is a low risk of addiction or increased mental health concerns.

3) Pay attention to changes that don’t feel like “typical teen stuff”

If cannabis use is happening alongside shifts in mood, sleep, motivation, friends, or a noticeable drop in grades, it’s worth taking seriously and seeking a professional evaluation. Also keep an eye out for paranoia, agitation, or unexplained illness. Using weekly is a strong warning sign than a teen is in need of help.

4) If there’s a family history of serious mental illness, be extra cautious

Mental health disorders are complex and influenced by multiple factors (genetics, environment, stress, trauma, and more). Some teens may be more vulnerable than others.

A final word: prevention is powerful, treatment works, and support is available

For many families, the hardest part is knowing when experimentation has crossed into something that needs help. The earlier you address substance use and mental health concerns, the more options you typically have—and the more you can protect school performance, relationships, and long-term wellbeing.

If you’re worried about your teen or young adult, consider reaching out for a professional assessment. You don’t need to wait for a crisis to get support. Call today (513.792.1272) to talk to an intake specialist about your situation and learn more about our services and how we can help.

Sources:

https://www.npr.org/2026/02/21/nx-s1-5719338/cannabis-marijuana-weed-teens-psychosis-jama

https://jamanetwork.com/journals/jama-health-forum/fullarticle/2845356