Summary:
Adolescence is a critical period of brain development, during which cannabis exposure may affect cognitive functioning. While rates of cannabis use among young people have remained relatively stable, factors such as increased potency, changes in methods of use, and a lack of understanding of risk may influence its use. THC (delta-9-tetrahydrocannabinol) is the main psychoactive compound in cannabis, meaning it is the substance that produces the ‘high’. It acts on the brain by binding to cannabinoid receptors, which are part of the endocannabinoid system. THC interacts with brain systems involved in learning, memory, and behaviour, and earlier research has linked adolescent cannabis use to poorer outcomes in areas such as memory, attention, and processing speed. This longitudinal cohort study examined how initiating cannabis use during adolescence relates to changes in cognitive performance over time. Data was drawn from a sample of over 11,000 participants aged 9-17 years. Cannabis use was assessed using both self-report and biological measures. Analyses controlled for a range of factors such as demographics, family history, mental health, and other substance use. Results showed that adolescents who began using cannabis followed different cognitive trajectories compared to non-users. Although they often demonstrated slightly better cognitive performance before use, their rate of improvement over time was reduced across domains including memory, attention, processing speed, and working memory. Additional analyses indicated that THC exposure was associated with poorer memory outcomes over time. These findings suggest that initiating cannabis use during adolescence may disrupt typical cognitive development, particularly in memory-related functions. These associations remained after adjusting for multiple confounding factors.
Abstract:
Adolescents experience extensive neurocognitive development, with cannabis use potentially impacting developmental trajectories. Here, we comprehensively assess the influence of adolescent cannabis use onset on neurocognitive trajectories and consider how recent delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) may influence neurocognition. We use the large, diverse longitudinal Adolescent Brain Cognitive Development (ABCD) Study dataset, combining self-reported substance use with objective toxicological tests (hair, urine, breath, oral fluid). Longitudinal mixed methods of the full cohort (n = 11,036, ages 9-17; 47% Female/53% Male) investigate time-varying cannabis onset on neurocognitive performance. Primary model covariates include sociodemographics, family history of substance use disorder, prenatal substance exposure, early psychopathology, other substance use, and nesting for participant ID, study site, and family ID. Secondarily, in participants with repeat toxicological hair testing (n = 645; 38% Female/62% Male) at ages 12-16, we consider the influence of THC v. CBD v. Controls. Primary models included false discovery rate corrections (FDR-p < .05) while secondary models were interpreted at p < .01. Cannabis group interacted with age to show altered neurocognitive trajectories across domains (immediate recall and delayed memory, processing speed, inhibitory control, visuospatial processing, language, and working memory; βs = -0.11- -0.52). Secondary models indicated hair-identified THC exposure*age predicted worse episodic memory than in Controls (β = -0.60, p = .007), with no difference between CBD exposed and Controls. Data suggest those who use cannabis show likely pre-existing better cognitive performance during late childhood, with reduced improvement or flattened trajectories over time. These neurocognitive trajectories in youth (ages 9-17) who initiate cannabis use were demonstrated after accounting for within-person change and numerous known confounds and improving accuracy in identifying cannabis use through incorporating toxicological measures. Continued monitoring of this cohort will clarify cannabinoid-cognition relationships into young adulthood, including the impact of timing of cannabis use initiation.
Article Publication Date: 20/04/2026
DOI: 10.1038/s41386-026-02395-1
