NORML | January 21, 2016
Los Angeles, CA: The cumulative use of cannabis by adolescents has no direct effect on intelligence decline, according to longitudinal data published in the Proceedings of the National Academy of Sciences.
Investigators at the University of California, Los Angeles and the University of Minnesota evaluated whether marijuana use was associated with changes in intellectual performance in two longitudinal cohorts of adolescent twins. Participants were assessed for intelligence at ages 9 to 12, before marijuana involvement, and again at ages 17 to 20.
Researchers reported no dose-response relationship between cannabis use and IQ decline. They also found no significant differences in performance among marijuana using subjects when compared to their non-using twins.