In patients with depression, the HPA axis is activated, and the paraventricular nucleus of the hypothalamus synthesizes and releases corticotropin-releasing hormone (CRH) and arginine vasopressin, which are then transported to the anterior pituitary gland and stimulate the secretion of adrenocorticotropic hormone (ACTH) into the systemic circulation. This evidence concerns the gene POMC and major depressive disorder.