The available literature also considers the relevance of altered neuropeptides in the pathophysiology of MDD, including galanin (GAL), cholecystokinin (CCK), neuropeptide Y (NPY), oxytocin (OXT), vasopressin (VP), neuropeptide S (NPS), and melanin-concentrating hormone (MCH) [46]. This evidence concerns the gene PMCH and major depressive disorder.