LEXINGTON, Ky. — A landmark study of more than 11,000 American youth has found that teenagers who begin using cannabis show slower gains in thinking and memory skills as they grow, adding to growing concerns about cannabis use among young people in Kentucky. The research, reported by Kentucky Hea lth News, was published Monday in the journal Neuropsychopharmacology and analyzed data from the Adolescent Brain Cognitive Development Study, the largest long-term study of brain development in U.S. youth. Researchers from the University of California San Diego followed 11,036 children from ages 9 to 10 through ages 16 and 17, tracking both their cognitive performance and substance use. The findings show that across a range of skills — including memory, attention, language and processing speed — teens who used cannabis showed restricted growth over time compared to those who did not. In some cases, cannabis users performed well initially but their progress leveled off as they got older, while their peers continued to improve. “Adolescence is a critical time for brain development, and what we’re seeing is that teens who start using cannabis aren’t improving at the same rate as their peers,” said Natasha Wade, PhD, assistant professor of psychiatry at UC San Diego and lead author of the study. “These differences may seem small at first, but they can add up in ways that affect learning, memory and everyday functioning.” Researchers found that tetrahydrocannabinol (THC), the main intoxicating ingredient in cannabis, appeared to be the primary driver of cognitive changes. Teens with evidence of THC exposure showed worse memory over time, while those with cannabidiol (CBD) alone did not show the same pattern, though that group was smaller. The study’s findings have particular relevance in Kentucky, where cannabis-related emergency department visits among youth have surged. According to a report from the Kentucky Injury Prevention and Research Center, cannabis-related poisonings among Kentuckians under age 18 rose 43 percent between 2023 and 2024, from 124 to 212 visits, raising concerns about unintentional exposures and increased household access to cannabis products. While the study does not prove cannabis use directly causes cognitive changes — researchers note that environment and personality may play roles — the team accounted for many influences including family background, mental health and prior cognitive performance. The researchers plan to continue tracking participants into young adulthood to better understand the long-term effects of cannabis use and how timing and frequency of use may shape brain development. “Delaying cannabis use supports healthy brain development,” Wade said. “As cannabis becomes more widely available, it’s important for families and teens to understand how it may affect the developing brain.” This article was generated by AI (claude-haiku-4-5-20251001) based on source material from Kentucky Health News, enriched with 2 web searches. The original source is available at https://kyhealthnews.net/2026/04/20/largest-u-s-study-finds-teen-cannabis-use-linked-to-slower-cognitive-development/. The post Largest U.S. study links teen cannabis use to slower cognitive gains appeared first on The Lexington Times. ...read more read less