The potential inflammatory biomarker of bipolar disorder: Neutrophil-to-lymphocyte Ratio – A hospital-based cross-sectional study

Inflammation has been hypothesized as one of the pathophysiological factor for mood disorders. The neutrophil-to-lymphocyte ratio (NLR) has been proposed as a potential peripheral biomarker of mood episodes, as this is an economical and accessible marker of inflammation. This study aims to determine the role of inflammation in the pathophysiology of bipolar disorder (BD) and the potential of NLR as a marker for differentiating mood disorders. A cross-sectional study was conducted on 195 patients who met the inclusion criteria, of whom 80 were diagnosed with BD (mania), 47 with BD (depression), and 68 with major depressive disorder (MDD). Sociodemographic details and a blood sample were taken for hemogram measures. The NLR and MLR were calculated using the following formula: NLR = neutrophil count/lymphocyte count and MLR = monocyte count/lymphocyte count, and statistical analysis was done. The mean age (±standard deviation) of patients with mania, bipolar depression, and MDD were 35.97 (±13.14), 39.27 (±14.28), and 33.41 (±13.21) years, respectively, with an almost equal representation of male and female gender. The NLR ratio of 2.41 ± 0.84 was highest in BD (mania), followed by 1.75 ± 0.41 in bipolar depression and 1.67 ± 0.45 in MDD, which was significant (P < 0.001), while MLR ratio in BD (mania) was highest, followed by MDD and bipolar depression. Our result indicates NLR as a marker of differentiation and, thus, strengthens the pathophysiological importance of inflammation in mood disorders.