Tsuchimine S, Hattori K, Ota M, et al. - In patients with schizophrenia, major depressive disorder (MDD), or bipolar disorder (BD) vs healthy controls, researchers ascertained if plasma orexin-A levels vary. In addition, the possible associations between plasma orexin-A levels and clinical variables were investigated. The study sample consisted of 80 patients with schizophrenia, 80 patients with MDD, 40 patients with BD, and 80 healthy controls. By an enzyme-linked immunosorbent assay, plasma orexin-A levels were quantified. No connection was found between plasma orexin-A levels and any clinical symptoms, depression severity, or medication doses. According to findings, plasma orexin-A levels in BD patients are significantly lower vs healthy controls, which infers that, at least in a proportion of BD, low plasma levels of orexin-A play a role. However, further clinical studies with bigger sample sizes and preclinical studies would be needed to study the mechanisms underlying the altered orexin-A levels in BD to understand the clinical implications of plasma orexin-A concentrations.