WHY IT MATTERS: If you are a parent or caregiver of a teen, or a young person using cannabis yourself, this research reinforces that delaying use until the brain is more fully developed, typically into the mid-20s, is one of the most important harm reduction strategies available. CLINICAL OVERVIEW: Emerging research continues to reinforce what clinicians have observed for years: adolescent cannabis use, particularly during critical neurodevelopmental windows, is associated with a meaningful increase in risk for serious psychiatric conditions including psychotic and bipolar disorders. The developing brain remains uniquely vulnerable to exogenous cannabinoids, and the endocannabinoid system plays a central role in synaptic pruning and neural circuit maturation during the teenage years.