A UC San Diego study reveals that teens using cannabis experience slower cognitive growth compared to their non-using peers, impacting memory and learning.
Research from the University of California San Diego indicates that teenagers who begin using cannabis may face slower cognitive development, particularly in memory and other cognitive functions. Published in Neuropsychopharmacology, the study analyzed data from over 11,000 adolescents in the Adolescent Brain Cognitive Development (ABCD) Study, which delves into brain development trends among youth in the U.S.
Lead author Natasha Wade, PhD, of the UC San Diego School of Medicine, emphasized that adolescence is a critical period for cognitive growth. Her findings suggest that teens who engage in cannabis use do not advance cognitively at the same pace as their non-using peers. "While the differences might seem minor initially, they can accumulate and impact learning and daily functioning," Wade stated.
The longitudinal study tracked 11,036 participants as they transitioned from ages 9-10 to 16-17, measuring cognitive performance alongside cannabis consumption and other substance use. Utilizing self-reports and biological testing, including hair, urine, and saliva samples, researchers gained a nuanced understanding of cannabis exposure, ranging from recent to several months prior.
Results showed that teenagers who used cannabis exhibited slower cognitive enhancements in areas such as memory, attention, language, and processing speed. Initially, some of these users showed comparable or even superior cognitive performance at younger ages. However, as they began using cannabis, their cognitive development plateaued while their peers who abstained continued to make gains.
Additionally, the study investigated the effects of specific cannabis compounds. Among a subset of participants, those with tetrahydrocannabinol (THC) exposure—cannabis's primary psychoactive component—demonstrated more significant declines in memory performance over time compared to non-users. Interestingly, those exposed to cannabidiol (CBD) did not exhibit the same decline, though this group was relatively small.
"These findings suggest that THC may be a significant contributor to the observed cognitive changes," Wade commented, underscoring the complexity of cannabis products, particularly since some labeled as CBD may still contain THC.
While the cognitive discrepancies noted in the study were modest, the researchers contend that even slight changes can have substantial implications, as adolescent brain development is rapid and critical. These shifts could significantly affect academic performance and everyday functioning.
The study does not definitively conclude that cannabis usage directly causes slower cognitive growth; other elements such as environmental factors and personality traits could also be relevant. However, researchers took steps to account for various influences, including family background, mental health, and pre-existing cognitive abilities before cannabis use began.
Ongoing Research into Long-term Effects
The researchers plan to follow these individuals into young adulthood to further investigate long-term outcomes associated with cannabis use. Future studies aim to clarify how the timing and frequency of cannabis consumption shape brain development. "Delaying cannabis use fosters healthier brain development," Wade advised, highlighting the importance of clear information for teens and families as cannabis becomes more accessible.
Additional co-authors contributing to the study include Ryan M. Sullivan, Alexander L. Wallace, Veronica Szpak, Joanna Jacobus, and Susan F. Tapert from UC San Diego; Rachel Visontay, Louise Mewton, and Hollie Byrne from the University of Sydney; Krista M. Lisdahl from the University of Wisconsin-Milwaukee; Marilyn A. Huestis from Huestis & Smith Toxicology; and Priscila Dib Gonçalves from Columbia University.
The study received partial funding from the National Institute on Drug Abuse, among other sources.
Materials provided by University of California - San Diego. Content may be edited for style and length.
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