**Abstract**

The cells of our body comprise calcitriol (1,25(OH) vitamin D2), the active form of vitamin D, an integral biological substance that has an impact on a large number of biological processes. While high prevalence of vitamin D deficiency is detected in population worldwide, the reports from sun-soaked countries like India are also alarming to note that the deficiency of vitamin D as high as 70 to 90% is observed leading to several chronic diseases in the majority of people. Deficiency of vitamin D is observed not only because of low levels of vitamin D in the diet, less exposure to sunlight, reduced cutaneous vitamin D synthesis, but also due to consumption of particular medicines, undue alcohol intake, and tobacco smoking. Vitamin D is known to affect estradiol, dopamine, and pro-inflammatory cytokine levels, besides being involved in the regulation of mechanisms pertaining to hormones like glucocorticoids. When vitamin D binds to vitamin D receptors (VDR) present in the central nervous system, it is noted to be responsible for the regulation of brain neuronal functions. Low 25-hydroxy vitamin D levels are found to have a higher incidence of various mood disorders. This review focusses on vitamin D receptors, VDR gene mutations, and pathophysiology causing vitamin D deficiency disorders.

**Keywords:** vitamin D, VDR receptors, mood disorders, deficiency, insufficiency, cognition
