The following is a summary of “Molecular brain differences and cannabis involvement: A systematic review of positron emission tomography studies” published in the June 2023 issue of Psychiatric Research by Xu, et al.

Many studies have employed positron emission tomography (PET) to examine molecular neurobiological differences in cannabis users. The objective of this study was to conduct a comprehensive review of PET imaging research on cannabis users and those with cannabis use disorder (CUD). A thorough systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria using the PubMed, Scopus, PsycINFO, and Web of Science databases.

Twenty studies in total were identified and categorized according to three themes: Studies of the dopamine system primarily found that cannabis use was associated with abnormal striatal dopamine synthesis capacity, which was correlated with clinical symptoms; studies of the endocannabinoid system found that cannabis use and CUD are associated with lower cannabinoid receptor type 1 availability and global reductions in fatty acid amide hydrolase binding; studies of brain metabolism found that individuals who use cannabis exhibit low levels of fatty acid amide hydrolase binding; Meta-analysis was impeded by heterogeneity between studies. 

Existing PET imaging research reveals substantial molecular differences between cannabis users and non-users in the dopamine and endocannabinoid systems, as well as in global brain metabolism, despite a high degree of heterogeneity in research designs and approaches, and it is unclear whether these differences are causal or consequential.

Source: sciencedirect.com/science/article/abs/pii/S0022395623001644