Age-related differences in the impact of cannabis use on the brain and cognition: a systematic review

Abstract

The impact of cannabis on the adolescent compared to adult brain is of interest to researchers and society alike. From a theoretical perspective, adolescence represents a period of both risk and resilience to the harms of cannabis use and cannabis use disorders. The aim of this systematic review is to provide a critical examination of the moderating role of age on the relationship between cannabis use and cognition. To this end, we reviewed human and animal studies that formally tested whether age, adolescent or adult, changes the relationship between cannabis exposure and cognitive outcomes. While the results of this review do not offer a conclusive answer on the role of age, the novel review question, along with the inclusion of both human and animal work, has allowed for the formation of new hypotheses to be addressed in future work. First, general executive functioning seems to be more impaired in adolescent frequent cannabis users compared to adult frequent cannabis users. Second, age-effects may be most prominent among very heavy and dependent users. Third, craving and inhibitory control may not decrease as much post-intoxication in adolescents compared to adults. Lastly, adolescents' vulnerability to reduced learning following cannabis use may not persist after sustained abstinence. If these hypotheses prove correct, it could lead to important developments in policy and prevention efforts.

Keywords: Adolescence; Brain; Cannabis; Cognition; Development; Systematic review.

Fig. 1

PRISMA flow diagram detailing our screening process

Fig. 2

Cognitive domains assessed in rat studies across the literature are in circles, as described in a seminal review paper (see [28]). The second layer of boxes contains the narrower cognitive function along with the behavioral tasks typically used to assess that function. Asterisks represent cognitive functions or tasks that were not assessed or used in the included studies covered in this review. The third layer of boxes contains short descriptions for the tasks used across the included studies. The numbers in brackets are the citation for the study/studies that used the task. It should be noted that these are general overviews of the tasks used across our included studies; therefore, there may be slight variations in how the task was administered. Additionally, even though Pre-Pulse Inhibition is mostly used in schizophrenia research to assess sensorimotor deficits, here we mostly used and interpreted this measure as a reflection of pre-attention processes