Neuropeptides, including enkephalin, cholecystokinin (CCK), and substance P/tachykinins, are a diverse group of neurotransmitters associated with pain and inflammation, which, together with their receptors, are considered as potential therapeutic targets in human mood disorders and neuropsychiatric disorders in rodent studies and in studies involving addicted patients [7,50,51,52]. The gene discussed is CCK; the disease is mood disorder.