Abstract
(1) Background: Recent research suggests inflammation as a factor involved in the pathophysiology of mood disorders. Neutrophil-to-lymphocyte (NLR), monocyte-to-lymphocyte (MLR), platelet-to-lymphocyte (PLR), and systemic immune-inflammatory (SII) index ratios have been studied as peripheral markers of inflammation in bipolar and major depressive disorders. The purpose of this study is to comparatively analyze these inflammatory ratios among manic episodes of bipolar disorder, bipolar depression and unipolar depression. (2) Methods: 182 patients were retrospectively included in the study and divided into three groups: 65 manic patients, 34 patients with bipolar depression, and 83 unipolar depressive patients. White blood cells, neutrophils, monocytes, lymphocytes, and platelets were retrieved from the patients’ database. NLR, MLR, PLR, and SII index were calculated using these parameters. (3) Results: Patients with manic episodes had elevated NLR (p < 0.001), MLR (p < 0.01), PLR (p < 0.05), and SII index (p < 0.001) compared to unipolar depression and increased NLR (p < 0.05) and SII index (p < 0.05) when compared to bipolar depression. NLR (p < 0.01) and SII index (p < 0.05) were higher in the bipolar depression than unipolar depression. NLR is an independent predictor of the bipolar type of depression in depressive patients. (4) Conclusions: The results confirm the role of inflammation in the pathophysiology of mood disorders and suggest the ability of NLR as a marker for the differentiation of bipolar from unipolar depression.
Highlights
Bipolar disorder (BD) and major depressive disorder (MDD) are common chronic psychiatric illnesses, with a prevalence in the general population of 1–1.1% and 16.2%, respectively [1,2,3]
In line with previous reports that outlined differences between bipolar and unipolar depression in terms of inflammation, our study found that BD depressed patients had an increased subclinical inflammation, as reflected by the systemic immune-inflammatory (SII) index and neutrophil-to-lymphocyte ratio (NLR), when compared with MDD patients
We report important data regarding NLR, monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and the SII index, as inflammatory markers, and bipolar disorder and major depressive disorders
Summary
Bipolar disorder (BD) and major depressive disorder (MDD) are common chronic psychiatric illnesses, with a prevalence in the general population of 1–1.1% and 16.2%, respectively [1,2,3]. BD is defined by mood fluctuations that range from mania or hypomania to depression and periods of euthymia, while MDD patients experience only depressive episodes [4]. BD and MDD play a major contribution to the impact on the work and social life of the patients. Among hypothalamic–pituitary–adrenal axis dysregulation, monoamine and glutaminergic neurotransmission alterations or neurotrophins imbalance, inflammation and immune dysfunctions have been proposed as possible underlying pathways in mood disorders, both MDD and BD [2,7,8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
