Study: Cannabis Use Has “No Lasting Residual Effects On Neurocognitive Performance”

Orlando, FL: The use of cannabis is not associated with "enduring negative effects" on the cognitive skills in moderate to heavy marijuana consumers, according to a meta-analysis to be published in the journal Experimental and Clinical Psychopharmacology.

A pair of researchers from the University of Central Florida, Department of Psychology reviewed various, peer-reviewed studies assessing whether cannabis use is associated with lasting adverse residual effects on cognition. They reported that cannabis chronic consumption may be associated with "small but significant" effects on neurocognitive skills for limited periods of time lasting beyond the immediate hours of intoxication. By contrast, authors found "no evidence of lasting effects on cognitive performance due to cannabis use" in subjects whose abstention period was at least 25 days.

Researchers concluded: "As hypothesized, the meta-analysis conducted on studies evaluating users after at least 25 days of abstention found no residual effects on cognitive performance. … These results fail to support the idea that heavy cannabis use may result in long-term, persistent effects on neuropsychological functioning."

Clinical trial data published in 2011 in the journal Addiction similarly reported "no significant differences associated with cannabis consumption" on various measures of memory and intelligence in over 2,000 self-identified marijuana consumers and non-users over an eight-year period. Authors of the study concluded, "[T]he adverse impacts of cannabis use on cognitive functions either appear to be related to pre-existing factors or are reversible in this community cohort even after potentially extended periods of use."

For more information, please contact Paul Armentano, NORML Deputy Director, at: Full text of the study, "Residual effects of cannabis use on neurocognitive performance after prolonged abstinence: A meta-analysis," will appear in Experimental and Clinical Psychopharmacology.