Adolescent Cannabis Use Linked to Slower Cognitive Development

Researchers from University of California San Diego School of Medicine 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 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 School of Medicine 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.”

“These results point to THC as a likely driver of the changes we’re seeing,” Wade said. “It also highlights how complicated cannabis products can be, especially since some products labeled as CBD may still contain THC.”

While the differences seen in the study were relatively modest, researchers say they could still matter. During adolescence, the brain is rapidly developing, and even small changes in memory, attention or thinking speed can affect school performance and daily life.

The researchers note that the study does not prove cannabis use directly causes these changes. Other factors — such as environment or personality — may play a role. However, the team accounted for many of these influences, including family background, mental health and use of other substances, as well as for each participant’s prior cognitive performance.

The team will continue tracking participants into young adulthood to better understand the long-term effects of cannabis use, including 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.”

Reference: Wade NE, Sullivan RM, Wallace AL, et al. Longitudinal neurocognitive trajectories in a large cohort of youth who use cannabis: combining self-report and toxicology. Neuropsychopharmacol. 2026. doi: 10.1038/s41386-026-02395-1

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