Porto, Portugal: Subjects who engage in the occasional use of cannabis during their teens exhibit no significant changes in cognitive functioning in young adulthood, according to longitudinal data published in the journal Psychopharmacology.
Portuguese researchers assessed reward-related brain activity, psychopathology, and cognitive functioning in a cohort of cannabis consumers and controls. Subjects in the study were all cannabis naïve at age 14. Investigators then conducted follow-up investigations when subjects were 19 and 22 years of age.
Researchers did not identify any significant cognitive differences at age 22 between occasional cannabis consumers and abstainers.
“After cannabis use initiation, light CAN [cannabis users] and CON [controls] did not differ in internalizing psychopathology, cognitive functioning, or brain activity,” the study’s authors concluded. “Overall, future longitudinal studies should oversample participants with higher frequency of cannabis use and follow them through midlife to re-evaluate this pattern of findings.”
Other studies have similarly failed to identify significant changes in either brain morphology or IQ specifically attributable to adolescents’ cannabis use.
Full text of the study, “Light cannabis use and the adolescent brain: An 8-years longitudinal assessment of mental health, cognition, and reward processing,” appears in Psychopharmacology. Additional information is available from the NORML Fact Sheet, ‘Marijuana Exposure and Cognitive Performance.’