Cannabis and Cognitive Systems in Adolescents

Background: Cannabis (marijuana) is used by half of all adolescents. Commonly held beliefs that this psychoactive substance is harmful to adolescents coexist with views that cannabis is a harmless natural substance that has beneficial effects. These culturally-ingrained attitudes can have more powerful effects on policy and behavior than experimental evidence. It is important to address the potential imbalance between the influence of cultural attitudes and objective data especially during this period when official sanction of cannabis is in transition across the United States.

Methods: This review presents the scientific literature on neuropsychological functioning in adolescents who use cannabis. These experimental data are organized along the constructs of the cognitive systems domain delineated by the Research Domain Criteria (RDoC) of NIMH. Review of data on social and emotional functioning in cannabis-using adolescents is not a focus of this article.

Results: Adolescents who use cannabis regularly and heavily have impairments in a number of areas of cognition that include attention, declarative memory, and cognitive control. Some impairments may be dose dependent, worse the younger the age of initiation, and persistent in abstinence. The ways in which gaps in this literature hinder the interpretation and broad application of the findings are described.

Conclusions: There are sufficient research data to raise concerns that regular cannabis use is detrimental to mental functioning of adolescents. The literature suggests that because the adolescent brain is developing, it is more sensitive to any adverse effects of cannabis. Still, further research is needed to better understand cannabis and the brain, specifically accounting for neurocognitive functioning before initiation of cannabis, different degrees of use, and the long-term consequences of use and abstinence.