A new study has delivered some very inconvenient news for the “weed is harmless” crowd: teenagers who use marijuana face a significantly higher risk of serious mental health problems later in life. The research, published Friday in the JAMA Health Forum, found that adolescent cannabis use is associated with increased chances of developing psychotic disorders, bipolar disorder, anxiety, and depression over time.
According to reporting from NPR, the researchers analyzed health data from about 460,000 teenagers in Northern California and followed them until age 25. To avoid muddying the waters, teens who already showed signs of mental illness before using marijuana were excluded from the study. In other words, this wasn’t about kids who were already struggling — this was about what happened after marijuana entered the picture.
The results were hard to ignore. Teens who reported using marijuana doubled their risk of developing bipolar disorder and psychotic disorders, including schizophrenia. Only a small fraction — roughly 4,000 — were diagnosed with each condition, but these illnesses are among the most severe and disabling mental disorders known.
Columbia University psychiatrist Dr. Ryan Sultan didn’t sugarcoat it, telling NPR, “This is very, very, very worrying.” Translation: this is not the kind of data you want to see while politicians and activists race to normalize drug use among young people.
The study’s authors noted that their findings should guide “clinical and educational interventions” and even “protective policies” to prevent or delay teen cannabis use as legalization spreads. Funny how reality keeps interrupting the narrative.
There’s also a massive price tag attached to all this. NPR pointed out that while the U.S. cannabis market is now worth tens of billions of dollars, the societal cost of schizophrenia alone has been estimated at $350 billion per year. So yes, someone’s getting rich — and it’s not the families dealing with lifelong mental illness.
Back in December, Columbia University Irving Medical Center reported that about one in five high school students uses cannabis. Scientists are especially alarmed because today’s marijuana products contain two to three times more THC than in the past, making them far more potent. And since the adolescent brain is still developing critical neural connections, cannabis use may leave lasting damage to thinking, learning, and academic performance.
To make things even more encouraging (sarcasm fully intended), experts told the Associated Press in 2025 that more Americans are addicted to marijuana — but fewer are seeking help.
So while legalization advocates celebrate profits and cultural acceptance, the data keeps pointing in the same direction: teen marijuana use isn’t “no big deal.” It’s a risk factor for some of the most devastating mental illnesses we know.
The good news? Studies like this cut through the smoke. With real evidence on the table, parents, schools, and policymakers now have a stronger case to protect kids instead of experimenting on them. And that’s a step in the right direction — for families, for communities, and for the next generation.
