UC San Diego Health Sciences Apr 20 2026 Researchers from University of California San Diego have found that teenagers who begin using cannabis show slower gains in thinking and memory skills as they grow. The study, published on April 20, 2026 in Neuropsychopharmacology , analyzed data from more than 11,000 participants in the Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term study of brain development in U.S. youth. "Adolescence is a critical time for brain