VDR and major depressive disorder: The discovery of vitamin D receptor (VDR) (Haussler et al. 1969), and confirming its presence in various tissues has opened the mechanistic link between vitamin D and the occurrence of many diseases and disorders such as: obesity, a chronic, low-grade inflammatory state which aids in the pathogenesis of insulin resistance, metabolic syndrome, and type II diabetes mellitus, (McGill et al. 2008), cardiovascular risk (Kunadian et al. 2014), Alzheimer’s disease (Littlejohns et al. 2014), depression (Jhee et al. 2017) and cancer (Garland et al. 2006).