CCK and schizophrenia: Beyond that, several other neurotransmitters and neuropeptides, including oxytocin, serotonin, cortisol, GABA, cannabinoid, neuropeptide Y, neurotensin, cholecystokinin, corticotropin-releasing factor, and orexin, have been implicated in the neuropathophysiology of schizophrenia [8,9].