A massive study tracking nearly half a million California teens found that cannabis use significantly increases the risk of developing serious mental health conditions later in life. Researchers at Kaiser Permanente followed adolescents until age 25, examining annual health screenings and mental health diagnoses. The data revealed that teens who used cannabis in the past year had double the risk of developing bipolar and psychotic disorders compared to non-users.

Only about 1% of all teens in the study were diagnosed with these severe conditions, but the findings are alarming given the societal costs. Schizophrenia alone costs the U.S. an estimated $350 billion annually, potentially wiping out the entire value of the cannabis market. The study also found increased risks for more common conditions like depression and anxiety, though these links weakened for older teens, suggesting younger brains are particularly vulnerable to cannabis's effects on neurological development.

Psychiatrist Dr. Ryan Sultan notes that cannabis-induced psychotic episodes can be "neurotoxic" and lead to rapid brain deterioration, making recovery harder over time. The research design, which excluded teens already showing mental health symptoms, points to a potential causal relationship rather than just correlation. With teen cannabis use rising amid perceptions of safety, these findings challenge the narrative that legalization has made marijuana harmless.