Major Study Links Teen Cannabis Use to Slower Cognition

Researchers find adolescents who use cannabis show restricted growth in memory, attention and other skills over time.

Apr. 20, 2026 at 10:14am

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A ghostly, translucent X-ray image of a human brain, with glowing blue and grey lines revealing its intricate internal structures against a dark background, conceptually representing the effects of cannabis use on the developing adolescent mind.An X-ray view of the adolescent brain highlights the potential impact of cannabis use on cognitive development.San Diego Today

A new study from researchers at the University of California San Diego has found that teenagers who begin using cannabis show slower gains in thinking and memory skills as they grow older, compared to their peers who do not use cannabis. The study analyzed data from over 11,000 participants in the Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term study of brain development in U.S. youth.

Why it matters

The findings highlight the potential risks of cannabis use during adolescence, a critical period for brain development. Even small changes in cognitive abilities during this time can affect school performance and everyday functioning. As cannabis becomes more widely available, it's important for families and teens to understand how it may impact the developing brain.

The details

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, these teens performed just as well as or even slightly better than others when they were younger, but as they got older and started using cannabis, their progress leveled off while their peers continued to improve. The study also found that teens with evidence of tetrahydrocannabinol (THC) exposure showed worse memory over time than those who did not use cannabis, while teens with evidence of cannabidiol (CBD) did not show the same pattern.

  • The study was published on April 20, 2026 in the journal Neuropsychopharmacology.
  • Researchers followed 11,036 children starting at ages 9 to 10 through ages 16 and 17.

The players

Natasha Wade

PhD, assistant professor in the Department of Psychiatry at UC San Diego School of Medicine and lead author of the study.

University of California San Diego

The institution where the researchers who conducted the study are based.

Adolescent Brain Cognitive Development (ABCD) Study

The largest long-term study of brain development in U.S. youth, which provided the data analyzed in this study.

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What they’re saying

“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. These differences may seem small at first, but they can add up in ways that affect learning, memory and everyday functioning.”

— Natasha Wade, PhD, assistant professor in the Department of Psychiatry at UC San Diego School of Medicine

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

— Natasha Wade, PhD, assistant professor in the Department of Psychiatry at UC San Diego School of Medicine

What’s next

The researchers 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.

The takeaway

This study underscores the importance of delaying cannabis use during adolescence, a critical period for brain development. As cannabis becomes more widely available, it's crucial for families and teens to be aware of how it may impact cognitive abilities and everyday functioning.