Grey matter volume loss in Parkinson’s disease Psychosis and cannabinoid receptor gene expression in the brain

Background: Serotonergic and dopaminergic pathways are implicated in Parkinson’s Disease Psychosis (PDP), but preliminary evidence also implicates the endocannabinoid system. Objectives: We examined the association of grey matter volume loss in PDP patients with brain expression of the genes coding for CB1 and CB2 cannabinoid receptors obtained from an independent sample. Methods: Hedges’ g effect sizes indexing grey matter volume loss were extracted from a previous meta-analytic comparison of PDP and PD without psychosis. Relationship of cortical and subcortical CB1 and CB2 gene expression in six healthy individuals extracted from the Allen Human Brain Atlas with meta-analytic estimates of PDP-related volume loss was examined correcting for spatial autocorrelation. Results: There was a significant association between grey matter volume loss in PDP and CB1 (r=0.337, t(76)=3.122, p