Neuropsychological effects of cannabis use by continent and age: a systematic review

Introduction: Cannabis use during adolescence and young adulthood has been associated with neurocognitive alterations. However, limited attention has been paid to whether these findings vary according to developmental stage and regional context. This systematic review examined the neurocognitive effects of cannabis use in adolescents and young adults, with particular attention to age-related patterns and geographic variation.

Methods: Following PRISMA guidelines, a systematic search was conducted in PubMed/MEDLINE, Scopus, Web of Science, and OpenGrey for studies published between 1 January 2019 and 30 June 2024. Eligible studies assessed cognitive performance in adolescent or young adult cannabis users. Methodological quality was appraised using the Mixed Methods Appraisal Tool, and certainty in the body of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation approach.

Results: Twenty-two studies met the inclusion criteria. Across the included studies, memory-related impairments were the most consistent findings, particularly in episodic and working memory. Evidence regarding executive functions was more heterogeneous and appeared to vary according to age group, exposure profile, study design, and cognitive task. Studies from the Americas, many of them longitudinal, more often reported negative associations between cannabis use and cognitive performance. European findings were more mixed, possibly reflecting differences in product characteristics, co-use patterns, and measurement approaches. Evidence from Asia was limited.

Discussion: Overall, the findings suggest that cannabis-related neurocognitive differences are more consistently detected in adolescent samples than in young-adult samples, although this pattern is likely shaped by developmental, methodological, and contextual factors. Future research should improve comparability in exposure definitions, control of confounding variables, and selection of cognitive measures.