Teens who use weed before age 15 have more trouble later, a study finds

OG article by Tony Lange

October 30 2025

A Québec Longitudinal Study (1,500+ participants) published in JAMA Network Open found teens starting cannabis before 15 and using frequently by 17 (20% of users) have 51% higher odds of mental health care and 86% higher odds of physical health care (e.g., respiratory issues, injuries) in young adulthood—after controlling for bullying, parenting, and peer factors. Early frequent users are more likely to become heavy adult users. Experts (Ryan Sultan, Krista Lisdahl) warn adolescent brains are vulnerable; regular use disrupts executive function, emotion regulation, and coping skills. Recommendation: delay use until age 25.