Teen cannabis use is linked to slower cognitive growth, especially memory, with THC as a likely contributor during key developmental years.
Researchers at the University of California, San Diego, report that teenagers who begin using cannabis show slower improvement in thinking and memory skills as they age. The findings, published in the journal Neuropsychopharmacology, are based on 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 in the Department 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.”
The team tracked 11,036 children from ages 9 to 10 through ages 16 and 17, monitoring both cognitive performance and substance use. To better measure cannabis exposure, researchers combined self-reported data with biological testing, including hair, urine, and saliva samples, which can reveal drug use from recent days to several months.
Cognitive Growth Differences in Cannabis-Using Teens
Across multiple areas, including memory, attention, language, and processing speed, teens who used cannabis showed slower progress over time compared to non-users. Some performed similarly or slightly better than peers at younger ages. However, after they began using cannabis, their development slowed while others continued to improve.
The researchers also examined specific components of cannabis. In a smaller subgroup, teens with evidence of tetrahydrocannabinol (THC) exposure, the main intoxicating compound in cannabis, showed greater declines in memory over time than those who did not use cannabis. Teens with evidence of cannabidiol (CBD) did not show the same pattern, although the sample size was limited.
“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.”
THC Effects and Adolescent Cognitive Impact
Although the differences observed were modest, researchers say they may still have meaningful effects. During adolescence, the brain undergoes rapid development, and even small shifts in memory, attention, or thinking speed can influence school performance and daily functioning.
The study does not prove that cannabis use directly causes these changes. Other factors, such as environment or personality, may contribute. However, the researchers controlled for many influences, including family background, mental health, use of other substances, and each participant’s earlier cognitive performance.
The team plans to continue following participants into young adulthood to better understand the long-term effects of cannabis use, including how timing and frequency may influence 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: “Longitudinal neurocognitive trajectories in a large cohort of youth who use cannabis: combining self-report and toxicology” by Natasha E. Wade, Ryan M. Sullivan, Alexander L. Wallace, Rachel Visontay, Veronica Szpak, Krista M. Lisdahl, Marilyn A. Huestis, Priscila Dib Gonçalves, Hollie Byrne, Louise Mewton, Joanna Jacobus and Susan F. Tapert, 20 April 2026, Neuropsychopharmacology.
DOI: 10.1038/s41386-026-02395-1
The study was funded, in part, by the National Institute on Drug Abuse (DA050779, PI: Wade), (DA064409 PI: Sullivan), (DA062011 PI: Wallace), (T32 AA013525 PI: Riley/Spadoni to Szpak), (R01DA062432 MPI Lisdahl, Hillard), (2U01DA041025 MPI Lisdahl, Larson), (K01DA057389 PI: Gonçalves), and (NARSAD/Brain Behavior Research Foundation Gonçalves).
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