JAMA Study Links Teen Cannabis Use to Higher Psychosis Risk

A new longitudinal study in JAMA Health Forum that tracked 460,000 adolescents in Kaiser Permanente Northern California finds that teens who use cannabis face roughly double the risk of later being diagnosed with bipolar disorder or a psychotic disorder such as schizophrenia compared with non‑users. Researchers followed kids into their mid‑20s and excluded anyone who showed mental‑illness symptoms before using cannabis, strengthening the case that early use is a risk factor rather than just a marker of existing problems. The study also found cannabis‑using teens had about a one‑third higher risk of depression and a one‑quarter higher risk of anxiety, with harms more pronounced the younger the brain was at first exposure. Dr. Lynn Silver of the Public Health Institute warns the societal costs of additional schizophrenia cases alone could outweigh the economic value of the legal cannabis market, while Columbia University psychiatrist Dr. Ryan Sultan calls the findings "very, very, very worrying" for youth who see marijuana as a harmless, natural product. The results arrive as U.S. states continue expanding legal access and as social media normalizes teen use, adding hard numbers to a policy fight over how aggressively to warn and restrict minors.