Cortical surface morphology in long-term cannabis users: A multi-site MRI study

Cannabis exerts its psychoactive effect through cannabinoid receptors that are widely distributed across the cortical surface of the human brain. It is suggested that cannabis use may contribute to structural alterations across the cortical surface. In a large, multisite dataset of 120 controls and 141 cannabis users, we examined whether differences in key characteristics of the cortical surface - including cortical thickness, surface area, and gyrification index were related to cannabis use characteristics, including (i) cannabis use vs. non-use, (ii) cannabis dependence vs. non-dependence vs. non-use, and (iii) early adolescent vs. late adolescent onset of cannabis use vs. non-use. Our results revealed that cortical morphology was not associated with cannabis use, dependence, or onset age. The lack of effect of regular cannabis use, including problematic use, on cortical structure in our study is contrary to previous evidence of cortical morphological alterations (particularly in relation to cannabis dependence and cannabis onset age) in cannabis users. Careful reevaluation of the evidence on cannabis-related harm will be necessary to address concerns surrounding the long-term effects of cannabis use and inform policies in a changing cannabis regulation climate.