A fresh study published in JAMA Health Forum has found that adolescent cannabis use is linked to increased risks of developing bipolar and psychotic disorders, as well as anxiety and depression, years later. The longitudinal research, analyzing data from nearly 460,000 teenagers within the Kaiser Permanente Health System in Northern California, tracked participants up to age 25, examining substance use and mental health diagnoses.
Researchers deliberately excluded adolescents who already exhibited symptoms of mental illness prior to cannabis use, strengthening the study’s design. “We looked at kids using cannabis before they had any evidence of these psychiatric conditions and then followed them to understand if they were more likely or less likely to develop them,” explained Dr. Lynn Silver, a pediatrician and researcher at the Public Health Institute and one of the study’s authors.
The findings revealed that teens who reported recent cannabis use faced a significantly higher risk of later mental health diagnoses compared to their non-using peers. Specifically, cannabis use doubled the risk of developing bipolar disorder, characterized by alternating periods of depression and mania, and psychotic disorders, including schizophrenia. While the absolute number of diagnoses for these severe conditions remained relatively small – approximately 4,000 teens in each category – researchers emphasized the serious and debilitating nature of both bipolar and psychotic disorders.
“Those are the scarier conditions that we worry about,” said Dr. Ryan Sultan, a psychiatrist at Columbia University and cannabis researcher who was not involved in the study. He highlighted the substantial societal costs associated with these illnesses, noting that the economic burden of schizophrenia alone is estimated at $350 billion annually in the U.S. Dr. Silver added that an increase in these diagnoses could potentially negate the economic value generated by the burgeoning cannabis market.
The study also indicated elevated risks for more common mental health conditions. Depression rates were approximately 30% higher among cannabis users, while anxiety rates increased by about 25%. Notably, the correlation between cannabis use and depression/anxiety weakened for teens who initiated use at an older age, suggesting a greater vulnerability of the developing adolescent brain. “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,” Dr. Silver stated.
Researchers hope the findings will encourage greater caution among adolescents regarding cannabis use, challenging the perception of the drug as a safe and natural remedy. “With legalization, we’ve had a tremendous wave of this perception of cannabis as a safe, natural product to treat your stress with,” Dr. Silver said. “That is simply not true.”
Dr. Sultan emphasized the study’s strength in addressing the “chicken or the egg” dilemma often encountered in research linking cannabis and mental health. Previous studies have struggled to determine whether cannabis use contributes to the development of mental health issues or whether individuals predisposed to these conditions are more likely to use cannabis. By excluding participants with pre-existing mental health symptoms, the current study provides stronger evidence of a potential causal link.
Dr. Sultan, who reports observing an increase in teens presenting with new or worsening mental health symptoms alongside cannabis use in his clinical practice, noted that mental health disorders are complex and influenced by a multitude of factors, including genetics, environment, and lifestyle. He cautioned that cannabis use can exacerbate existing vulnerabilities. “When someone has a psychotic episode in the context of cannabis or a manic episode in the context of cannabis, clinicians are going to say, ‘Please do not do that again because you’re you’re you’re playing with fire,’” he said, adding that continued use can worsen symptoms and hinder recovery. He further explained that severe mood disorders can be “neurotoxic to your brain,” potentially leading to more rapid deterioration.
