Comprehensive UCSD Study Links Adolescent Cannabis Use to Stunted Cognitive Growth and Memory Retention Gains

Major UCSD study finds cannabis use in teens slows the development of memory and thinking skills compared to non-using peers.

By: AXL Media

Published: Apr 20, 2026, 8:17 AM EDT

Source: Information for this report was sourced from EurekAlert!

Identifying a Stagnation in Adolescent Mental Progression

Researchers at the University of California San Diego have released findings from the largest long-term study of American youth, suggesting that cannabis use during adolescence significantly hinders the natural growth of thinking and memory skills. Published on April 20, 2026, in Neuropsychopharmacology, the research indicates that as teenagers age, those who begin using cannabis fail to improve their cognitive abilities at the same rate as their abstinent peers. Assistant professor Natasha Wade, PhD, noted that while these developmental gaps may appear subtle in their early stages, they accumulate over time to potentially impair learning and daily functioning during a critical neurological window.

Rigorous Biological Monitoring within the ABCD Study Framework

The study analyzed data from 11,036 children participating in the Adolescent Brain Cognitive Development (ABCD) Study, following them from roughly age 10 through age 17. To ensure the accuracy of their findings, the research team utilized a combination of self-reported data and advanced biological testing, including hair, urine, and saliva samples. This multi-modal approach allowed scientists to detect drug exposure spanning several months, providing a much more reliable picture of substance use than surveys alone. This rigorous monitoring was essential for tracking how various cognitive domains, such as language and attention, fluctuated alongside substance exposure.

THC Exposure Linked to Declining Memory Trajectories

Within the broader findings, researchers identified tetrahydrocannabinol (THC) as a primary driver of cognitive interference. In a targeted analysis of a smaller participant group, those with confirmed THC exposure exhibited a marked decline in memory performance over time compared to non-users. Interestingly, a smaller group with evidence of cannabidiol (CBD) exposure did not display the same negative pattern, though researchers cautioned that the sample size for CBD-only users was limited. Dr. Wade emphasized that the presence of THC in products often marketed as CBD complicates the landscape for families and further suggests that the psychoactive component is responsible for the developmental disruptions.