#75 Strong Clinical Relevance
High-quality evidence with meaningful patient or clinical significance.
A large study found that moderate cannabis use in adults over 40 was linked to larger brain volumes and better cognitive function, though experts caution more research is needed before drawing conclusions.
A landmark longitudinal study published in JAMA Health Forum followed 463,396 adolescents ages 13-17 through age 26. Past-year cannabis use during adolescence was associated with a doubled risk of developing psychotic and bipolar disorders, plus elevated risks for depression and anxiety. Cannabis use preceded psychiatric diagnoses by an average of 1.7-2.3 years. Conducted by Kaiser Permanente, UCSF, and USC researchers using electronic health records from 2016-2023. With THC potency in flower exceeding 20% and concentrates far higher, the study underscores the urgency for youth-focused prevention regardless of legalization status.
“This is a provocative outlier that deserves rigorous follow-up,if the relationship between cannabis and cognition truly differs across the lifespan, it would fundamentally reshape how we counsel patients.”
THE JAMA STUDY: 460,000 TEENS AND THE PSYCHOSIS QUESTION
A landmark JAMA Health Forum study followed 463,396 adolescents ages 13-26. Cannabis use doubled psychosis and bipolar risk, preceded diagnoses by 1.7-2.3 years.
The massive cohort, clinical health record data, and high-potency era timing make this different from previous research. As a clinician, this reinforces that adolescent brains are uniquely vulnerable. Legalization advocates should lead the youth prevention conversation, not resist it. Acknowledging risk does not undermine reform. It strengthens it.
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For readers who would like a deeper examination of the studyโs methodology, statistical framing, and what these findings do and do not establish clinically, Iโve published a detailed review of the original JAMA Health Forum paper here: Adolescent Cannabis Use and Psychosis Risk โ Study Review .