Largest U.S. Study Finds Teen Cannabis Use Linked to Slower Cognitive Development

Key Points:

• A study by UC San Diego School of Medicine found that teenagers who start using cannabis exhibit slower improvements in memory, attention, and thinking skills compared to non-users, based on data from over 11,000 participants in the Adolescent Brain Cognitive Development Study.
• THC exposure, the main psychoactive component of cannabis, was specifically linked to worsening memory over time, while cannabidiol (CBD) did not show the same effect, highlighting THC as a likely driver of cognitive changes during adolescence.
• The research tracked cognitive performance and substance use from ages 9-10 through 16-17, combining self-reports with biological testing, and found that cannabis users' cognitive progress plateaued while their peers continued to improve.
• Although the observed cognitive differences were modest, they could impact school performance and daily functioning during critical brain development stages; the study controlled for various factors including mental health and other substance use.
• Researchers plan to continue monitoring participants into young adulthood to better understand long-term effects, emphasizing the importance of delaying cannabis use to support healthy adolescent brain development.