The effects of cannabis use on cognitive function in healthy aging: A systematic scoping review

Middle-to-older-aged adults (>50 years) represent the fastest-growing cannabis-using population. Given aging and cannabis use are associated with cognitive decline, it is important to establish the effects of cannabis on cognitive function in this population. This systematic scoping review used PRISMA guidelines to critically examine the extent of literature on this topic and highlight areas for future research. A search of six databases (PubMed, EMBASE, PsycINFO, Web of Science, Family and Society Studies Worldwide, and CINAHL) for articles published by September 2019, yielded 1,014 unique results. Only six articles reported findings for middle-to-older-aged populations (three human and three rodent studies), highlighting the paucity of research. Available human studies revealed largely null results, likely due to several methodological limitations. Nevertheless, the better-controlled rodent studies indicated an age and dose-dependent relationship between ∆9-tetrahydrocannabinol (THC) and cognitive function in aging. Extremely low doses of THC improved cognitive function in very old rodents. Somewhat higher chronic doses were required to improve cognitive function in moderately aged rodents. No studies examined the effects of cannabidiol (CBD) or high-CBD cannabis on cognition. Future research should examine the relevance of age and dose-dependent effects of THC in humans and the effects of CBD on cognitive function in aging.