According to a new study published in JAMA Psychiatry, “continued cannabis use may be associated with small reductions in cognitive functioning” on young brains but those deficits “are substantially diminished with abstinence.”
The study was a meta-analysis of 69 cross-sectional studies of 2,152 cannabis users and 6,575 comparison participants. The researchers found “a small but significant overall effect size for reduced cognitive functioning in adolescents and young adults who reported frequent cannabis use. However, studies requiring abstinence from cannabis for longer than 72 hours had a very small, nonsignificant effect size.”
“… Results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use. Reported deficits may reflect residual effects from acute use or withdrawal.” – Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults: A Systematic Review and Meta-analysis, Apr. 18, 2018, JAMA Psychiatry
The research concluded that, overall, the cognitive functioning of frequent cannabis users was reduced by one-third of a standard deviation compared with non-frequent marijuana users, which according to Cobb Scott, the lead author of the study, is a relatively small effect size
Scott, an assistant professor of psychiatry at the Perelman School of Medicine at the University of Pennsylvania admitted to CNN that the team was “surprised … that the effects were not bigger” than the analysis found, adding that the “clinical significance of a quarter of a standard deviation is somewhat questionable.”
“As attitudes change about cannabis use and cannabis use becomes a little bit more accepted in terms of policy and government regulation and medical cannabis use increases, I think we need to have a real understanding of the potential risks and benefits of cannabis use.” – Scott to CNN
The research could help dispel the prohibitionist arguments that long-term cannabis use will have lasting detrimental effects on cognitive functioning.