Evaluation of systemic immune inflammation index and neutrophil-to-lymphocyte ratio in schizophrenia, bipolar disorder and depression

Numerous studies consistently report on the frequent presence of low-grade systemic inflammation in individuals with schizophrenia, bipolar disorder (BD), and depression. Neutrophil-to-lymphocyte ratio (NLR) and a recently established marker, systemic immune inflammation index (SII), are markers used to assess systemic inflammation and immune response. In this study, NLR and SII index values were examined and compared across patients diagnosed with major psychiatric disorders and healthy controls. The study included, totaling 129 patients, encompassed individuals who were diagnosed with schizophrenia in remission or BD in the euthymic period, and those undergoing treatment for major depressive disorder (MDD). The control group consisted of 62 healthy individuals. White blood cell (WBC), neutrophil, lymphocyte, platelet, and monocyte counts obtained retrospectively from complete blood profiles served as the basis for calculating NLR and SII values. In this study, higher WBC, neutrophil counts, NLR, and SII values were observed in schizophrenia and BD patients compared to the control group. In patients with MDD, no significant difference was found in terms of inflammatory blood cell markers compared to healthy controls. Higher NLR and Sİİ values were found in patients with schizophrenia and BD compared to patients with MDD. The results of the study indicate that the significant difference in NLR and SII values persists after treatment in patients with schizophrenia and BD, and that the abnormal inflammatory response continues during the treatment process (Tab. 2, Ref. 41).