NR3C1 and major depressive disorder: MDD seems to be associated to HPA axis hyperactivity [241], as confirmed by hypercortisolism, one of the most consistent clinical features of MDD [246, 247], and desensitization of glucocorticoid receptor, the most important regulator of HPA axis negative feedback system [248] (variations in cortisol levels are directly related to the activation index of HPA axis [249]).