History of cannabis use and cognitive function in older adults: findings from the UK biobank

Background: Cannabis is a commonly used psychoactive drug, but its cognitive effects remain unclear, particularly in older adults. This study examined associations between past and present cannabis use and cognitive function among dementia-free older adults. Methods: Cross-sectional and longitudinal data were drawn from the UK Biobank, including adults aged ≥60 years. Cannabis use patterns were self-reported, and cognitive function was assessed via computerized tests of attention, executive function, processing speed, visual memory and working memory. Multivariable linear regression models adjusted for demographic, health and lifestyle-related covariates. Results: Cross-sectional analyses included 67 713 participants; longitudinal analyses included 52 002 participants with two cognitive assessments (mean age 67.2±4.4 years; 46.1% male). Lifetime cannabis users (17%) performed better across all cognitive domains: attention (B = 0.071), executive function (B = 0.047), processing speed (B = 0.363), visual (B = 0.062) and working memory (B = 0.181). Current use was associated with better working memory (B = 0.169). Mixed and contradictory results were found for early onset, duration and frequency of use with cognitive outcomes. Longitudinally, past use was associated with less decline in executive function, while longer duration of use predicted steeper decline in processing speed. Conclusions: Cannabis use is not uniformly harmful to cognition in older adults. Past use was linked to better performance and slower decline in some cognitive domains. However, specific usage patterns, such as longer duration, were associated with poorer outcomes in other domains. These findings highlight the need for further research to clarify underlying mechanisms and guide evidence-based recommendations regarding cannabis use in aging populations.