TUESDAY, April 21, 2026 (HealthDay News) -- Youth cannabis use between ages 9 and 17 years is associated with slower cognitive development during a time of key brain development, according to a study published online April 20 in Neuropsychopharmacology.Natasha E. Wade, from the University of California, San Diego, and colleagues used data from the Adolescent Brain Cognitive Development Study to assess the influence of adolescent cannabis use onset on neurocognitive trajectories. The analysis included self-reported substance use as well as objective toxicological tests (hair, urine, breath, and oral fluid) for 11,036 youths aged 9 to 17 years.The researchers found that within the cannabis group, there were age interactions showing altered neurocognitive trajectories across domains (immediate recall and delayed memory, processing speed, inhibitory control, visuospatial processing, language, and working memory; βs = −0.11 to −0.52). Hair-identified delta-9-tetrahydrocannabinol exposure by age predicted worse episodic memory versus controls (β = −0.60), but with no differences for cannabidiol-exposed individuals versus controls. In late childhood, those who used cannabis likely had preexisting better cognitive performance, but experienced reduced improvement or flattened trajectories over time. These neurocognitive trajectories in youth with cannabis use persisted when accounting for within-person change and numerous known confounders."Delaying cannabis use supports healthy brain development," Wade said in a statement. "As cannabis becomes more widely available, it's important for families and teens to understand how it may affect the developing brain."Abstract/Full Text.Sign up for our weekly HealthDay newsletter