POMC and major depressive disorder: A series of animal studies have shown that abnormal adrenocorticotropic hormone (ACTH) activity in patients with depression, which has also been confirmed in a clinical study where patients with depression often have hyperfunction of the HPA axis, causing an abnormal release of anterior pituitary ACTH, GC and corticotrophin-releasing hormone (CRH) (Meaney 2001; Meltzer et al.