Investigators affiliated with the University of Pennsylvania, Perelman School of Medicine and with the Children’s Hospital of Pennsylvania reviewed data from 69 separate studies published between 1973 and 2017 involving 8,727 subjects (2,152 frequent or heavy users and 6,575 controls). Researchers reported no significant long-term deficits in memory, attention, or other aspects of cognitive functioning that could be independently attributed to cannabis use, regardless of subjects’ age of initiation. These findings are in contrast to similar studies assessing the impact of alcohol use and other controlled substances on cognitive performance, which “have shown medium to large effect sizes.”
Authors concluded: “Associations between cannabis use and cognitive functioning in cross-sectional studies of adolescents and young adults are small and may be of questionable clinical importance for most individuals. Furthermore, abstinence of longer than 72 hours diminishes cognitive deficits associated with cannabis use. [R]esults indicate that previous studies of cannabis youth may have overstated the magnitude and persistence of cognitive deficits associated with marijuana use.”
For more information, contact Paul Armentano, NORML Deputy Director, at (202) 483-5500. Full text of the new study, “Association of cannabis with cognitive functioning in adolescents and young adults: A systematic review and meta-analysis,” appears in JAMA Psychiatry.