Reduced plasma orexin-A levels in patients with bipolar disorder
Received 17 March 2019
Accepted for publication 17 May 2019
Published 6 August 2019 Volume 2019:15 Pages 2221—2230
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Colin Mak
Peer reviewer comments 2
Editor who approved publication: Dr Taro Kishi
Shoko Tsuchimine,1 Kotaro Hattori,1 Miho Ota,1 Shinsuke Hidese,1 Toshiya Teraishi,1 Daimei Sasayama,1 Hiroaki Hori,1 Takamasa Noda,2 Sumiko Yoshida,2 Fuyuko Yoshida,1 Hiroshi Kunugi1
1Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan; 2Department of Psychiatry, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo 187-8551, Japan
Purpose: Orexins are hypothalamic neuropeptides involved in the regulation of sleep, appetite and arousal. An altered orexin system has been implicated in the pathophysiology of psychiatric disorders. This study aimed to examine whether plasma orexin-A levels differ in patients with schizophrenia, major depressive disorder (MDD), or bipolar disorder (BD) compared to in healthy controls. We also examined the possible correlations between plasma orexin-A levels and clinical variables.
Patients and methods: All participants were Japanese. The sample consisted of 80 patients with schizophrenia (42 women, 52.5%; mean age 36.8 years), 80 patients with MDD (43 women, 53.8%; 43.7 years), and 40 patients with BD (24 women, 60%; 41.1 years), as well as 80 healthy controls (48 women, 60%; 47.0 years). Plasma orexin-A levels were quantified by an enzyme-linked immunosorbent assay.
Results: Mean orexin-A levels were significantly different across the four diagnostic groups (F=4.09; df=3; p=0.007, η2=0.06). In particular, the patients with BD showed significantly lower orexin-A levels than did the controls. When the median value of the control group (109.8 pg/ml) was set as a cut-off value, subjects whose orexin-A levels were below the cut-off were more common in all psychiatric groups (schizophrenia: 73.8%, x2=9.56, df=1, p=0.003, OR=2.81, 95% CI: 1.45 to 5.45, d=0.57; MDD: 78.5%, x2=14.02, df=1, p<0.001, OR=3.65, 95% CI: 1.82 to 7.29, d=0.72; BD: 87.5%, x2=16.0, df=1, p<0.001, OR=7.00, 95% CI: 2.49 to 19.70, d=1.07). We found no association between plasma orexin-A levels and any clinical symptoms, depression severity, or medication doses.
Conclusion: Our results suggest that plasma orexin-A levels are reduced in patients with BD.
Keywords: orexin-A, plasma, schizophrenia, major depressive disorder, bipolar disorder
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