Cross-sectional study of neutrophil-lymphocyte, platelet-lymphocyte and monocyte-lymphocyte ratios in mood disorders

Neutrophil-lymphocyte, monocyte-lymphocyte and platelet-lymphocyte ratio are inexpensive and reproducible biomarkers of inflammation found to be elevated in mood disorders. This study aimed to compare inflammatory ratios between bipolar disorder and major depressive disorder and between bipolar disorder manic episodes and bipolar disorder depressive episodes.

We included 142 Caucasian patients (major depressive disorder: n = 36; bipolar disorder manic episode: n = 66; bipolar disorder depressive episode: n = 40). We measured white blood cells, neutrophils, lymphocytes, monocytes, platelets, glucose, and total cholesterol. Neutrophil-lymphocyte ratio, monocyte-lymphocyte ratio, and platelet-lymphocyte ratio were calculated.

Neutrophil-lymphocyte ratio and monocyte-lymphocyte ratio were significantly higher in bipolar disorder manic episodes when compared to bipolar disorder depressive episodes and major depressive disorder episodes after adjustment for age, sex, body mass index, and smoking.

To our knowledge, our study is the first one to compare inflammatory ratios between different bipolar disorder phases and major depressive disorder episodes. In accord with previous studies on other inflammatory mediators, we found higher neutrophil-lymphocyte and monocyte-lymphocyte ratios in bipolar manic episodes, suggesting that inflammatory changes occur especially during acute episodes of mania.