Sub-Regional Corpus Callosum Morphology in Marijuana Users

IntroductionThe primary psychoactive component in marijuana is tetrahydrocannabinol (THC), which acts on receptors, such as cannabinoid 1 (CB1), that are distributed broadly throughout the brain. THC interferes with synaptic plasticity and neurogenesis and impacts the brains macrostructure, specifically white matter where CB1 receptors are abundant. The current study aims to investigate whether callosal morphology differs depending on how much experience individuals have with marijuana. MethodsThis is a quantitative between-group corpus callosum morphology analysis using cohort study data. The data for this study (n = 144) came from the S1200 Release from the Washington University - University of Minnesota Human Connectome Project Consortium (WU-Minn HCP). Marijuana use was quantified using self-reports and grouped as (1) no use, (2) low use, and (3) high use. T1-weighted MRI brain images were obtained and then processed using SPM12 and MATLAB. Each corpus callosum was manually traced and automatically separated into seven callosal areas according to the Witelson parcellation scheme. The resulting area measures were compared between the three groups, while covarying for total brain volume. ResultsOur ANCOVA analysis was significant (F(2, 145) = 4.38, p = .014), and posthoc tests revealed a significantly smaller anterior midbody in the high marijuana use group compared to the no marijuana use group (p = .012). ConclusionSmaller callosal areas in the high use marijuana group suggest that heavy cannabis may be related to weaker interhemispheric connectivity. Future research is required to replicate the current findings using well-powered designs.