Neuropsychopharmacology
Teen cannabis use tied to slower cognitive gains
Clinical takeaway: As cannabis becomes more legal and accessible in the United States, clinicians should counsel families that delaying use until at least the minimum legal age of 21 supports healthier cognitive development.
Adolescent cannabis use has been linked to poorer cognitive performance, but prior studies were often smaller and relied heavily on self-reported data. This study was designed to test whether cannabis use onset tracks with slower cognitive development over time in a large U.S. youth cohort using both self-report and toxicology.
Investigators combined self-reported substance use with hair, urine, breath, and oral fluid testing, then modeled cognitive performance over time while accounting for sociodemographics, prenatal exposures, mental health, family history, and other substance use. Investigators followed more than 11,000 participants in the Adolescent Brain Cognitive Development study from ages 9 to 17.
The main signal was slower cognitive growth after cannabis use onset. Adolescents who used cannabis showed less improvement over time in immediate recall and delayed memory, processing speed, inhibitory control, visuospatial processing, language, and working memory. In a smaller subgroup with repeat hair testing, tetrahydrocannabinol (THC) exposure was associated with worse episodic memory over time, while cannabidiol (CBD) exposure wasn't clearly different from controls.
The findings suggest cannabis use during adolescence may blunt normal gains in cognition during a key developmental window, rather than cause an abrupt drop in performance. The THC result also points to the main intoxicating component of cannabis as a likely driver of the memory signal, although the CBD subgroup was small.
Researchers plan to follow this cohort into young adulthood and determine how age at onset, frequency of use, and continued exposure shape long-term cognitive trajectories. Future work should also clarify the separate roles of THC and CBD and test whether earlier prevention or delayed initiation changes outcomes.
“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 the University of California San Diego School of Medicine. “These differences may seem small at first, but they can add up in ways that affect learning, memory and everyday functioning.”
Source: Wade NE. Neuropsychopharmacology. 2026 Apr 20. Longitudinal neurocognitive trajectories in a large cohort of youth who use cannabis: combining self-report and toxicology