Recent cannabis use is negatively associated with working memory and visual memory in youth

Introduction: Cannabis is the most popular illicit recreational drug among youth globally. Evidence suggests that long-term heavy use of cannabis is negatively associated with important cognitive functions related to executive functioning, attention, and working memory, learning, and memory. Previous findings link the early onset of cannabis use to more extensive cognitive alterations. However, significant inconsistencies exist across studies. Method: In this cross-sectional study, we examined associations between cannabis use and cognitive performance across a broad range of cognitive tests (including a new test of visuo-spatial abilities, The Ruff-Light Trail Learning Test) in a sample of 109 Danes aged 15-26 with varying risk of developing harmful cannabis use and varying levels of current use. Cannabis use was evaluated using the Cannabis Use Disorder Identification Test-Revised (CUDIT-R) and questions on recent use (past 30 days) and age of onset. Cognitive performance was assessed using subtests from WAIS-IV, WMS-III, and the Ruff-Light Trail Learning Test. Results: Findings show a negative association between recent cannabis use and specific cognitive functions of working memory and visual memory, while the CUDIT-R was not associated with cognitive functions. Conclusion: Our findings nuance previous findings by suggesting differences in vulnerability across cognitive domains, while providing the first evidence of a negative association between recent cannabis use and visual memory based on visuo-spatial functions without requiring visuo-constructive abilities (Ruff-Light Trail Learning Test). Furthermore, findings suggest that past-month use may be a more relevant measure than CUDIT-R when evaluating cognitive correlates of cannabis use in youth. This has implications for treatment and preventive interventions in this age group.