Cannabis, cigarettes, and their co-occurring use: disentangling differences in default mode network functional connectivity
Drug and Alcohol Dependence June 10, 2015 R. Wetherill, Zhuo Fang, K. Jagannathan et al.
Co-occurring cannabis and tobacco use is associated with altered connectivity in the brain's default-mode network (DMN). Using resting-state functional MRI, researchers compared DMN connectivity in four groups: cannabis-dependent nonsmokers, cannabis-dependent tobacco smokers, tobacco-only smokers, and healthy controls. All substance-using groups showed lower DMN connectivity than controls, with distinct differences in connections involving the cerebellum, medial prefrontal cortex, parahippocampus, and anterior insula. Among cannabis-dependent individuals, stronger connectivity between the posterior cingulate cortex and right anterior insula correlated with longer duration of cannabis use. These findings suggest that both cannabis and tobacco exposure independently and jointly affect DMN function.