Neutrophil/Lymphocyte and Platelet/Lymphocyte Ratios as Inflammatory Biomarkers in Schizophrenia: A Cross-sectional Study from South India

Background: Schizophrenia is a chronic psychiatric disorder with a complex etiology involving genetic, neurobiological, and inflammatory mechanisms. Recent evidence highlights the role of systemic inflammation in schizophrenia, particularly through biomarkers such as the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR). However, the significance of these findings remains inconsistent, particularly in diverse populations. The aim of the study was to (1) evaluate systemic inflammation in schizophrenia by assessing NLR and PLR in antipsychotic treatment-responsive (TS) and treatment-resistant schizophrenia (TRS) patients compared to healthy controls, and (2) examine the association between NLR, PLR, and symptom severity. Materials and Methods: A case–control study was conducted at a tertiary mental health center in Chennai, South India. Participants included individuals diagnosed with schizophrenia (TS and TRS) and normal controls (NC). Clinical assessments included the Scale for the Assessment of Positive Symptoms, Scale for the Assessment of Negative Symptoms, and Global Assessment of Functioning. Blood samples were analyzed to determine NLR and PLR values. Statistical analyses included the Kruskal–Wallis test and generalized linear model. Results: Significant differences in NLR ( P < 0.0001) and PLR ( P = 0.007) were observed among the groups (TS = 88, TRS = 64, NC = 125). However, Spearman’s correlation showed weak and non-significant associations between NLR, PLR, and symptom severity ( r = −0.092–0.082, P > 0.05). Conclusion: Findings suggest that systemic inflammation is elevated in schizophrenia, particularly TRS, reinforcing the role of immune dysregulation. However, its direct clinical impact remains unclear, necessitating further research.