Small Link for Cannabis Use, Reduced Cognitive Functioning

Small overall effect size for frequent and heavy cannabis use among adolescents, young adults
Small overall effect size for frequent and heavy cannabis use among adolescents, young adults

HealthDay News — For adolescents and young adults, frequent or heavy cannabis use has a small association with reduced cognitive functioning, according to research published online April 18 in JAMA Psychiatry.

J. Cobb Scott, PhD, from the University of Pennsylvania in Philadelphia, Pennsylvania and colleagues conducted a quantitative synthesis of the literature examining cannabis and cognitive functioning in adolescents and young adults. Data were reviewed from 69 studies of 2,152 cannabis users (mean age, 20.6 years) and 6,575 comparison participants (mean age, 20.8 years) with minimal cannabis exposure. 

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The researchers observed a small overall effect size for reduced cognitive functioning associated with frequent or heavy cannabis use (d, −0.25). There was no variation in the magnitude of effect sizes by sample age or age at onset of cannabis use. The overall effect size was not significantly different from 0 for studies requiring an abstinence period longer than 72 hours, but was smaller than studies with less stringent abstinence criteria.

"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," the authors write.

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