 This study examined the levels of for neuropeptides, alpha-melanocyte stimulating hormone, MSH, beta-endorphin, neurotensin, and oxytocin in the cerebrospinal fluid, CSF, E and plasma of patients with schizophrenia, bipolar disorder, BD, and major depressive disorder, MDD. The results showed that the levels of these neuropeptides were similar across all three groups, suggesting that they are not involved in the pathophysiology of any of the conditions. Additionally, no correlation was found between the levels of these neuropeptides and either psychiatric symptom scores or cognitive function scores. This article was authored by Shinsuke Hides, Fuuko Yoshida, Iki Yoshida, and others.