Changes in Inflammatory Biomarkers in Patients with Schizophrenia: A 3-Year Retrospective Study

Objective: Accumulating evidence suggested that immune system activation might be involved in the pathophysiology of schizophrenia. The neutrophil/lymphocyte ratio (NLR), monocyte/lymphocyte ratio (MLR), platelet/lymphocyte ratio (PLR) and systemic immune-inflammation index (SII) can measure inflammation. This study aimed to investigate the inflammatory state in patients with schizophrenia by using these indicators. Methods: In this study, the complete blood count data for 187 continuing hospitalized patients with schizophrenia and 187 age-and sex-matched healthy participants was collected annually from 2017 to 2019. Platelet (PLT), lymphocyte (LYM), monocyte (MON) and neutrophil (NEU) counts were aggregated and NLR, MLR, PLR, and SII were calculated. Using a generalized linear mixed model, we assessed the impact of age, sex, diagnosis, and sampling year on the above indicators and evaluated the interaction between the factors. Results: According to the estimation results of the generalized linear mixed model, the NLR increased by 0.319 (p = 0.004), the MLR increased by 0.037 (p < 0.001), and the SII increased by 57.858 (p = 0.018) in patients with schizophrenia. Data after two years of continuous antipsychotic treatment showed that the NLR and MLR were higher in patients with schizophrenia than those in healthy controls, while the PLT and LYM counts were decreased in patients with schizophrenia. The schizophrenia diagnosis was correlated to the MON and LYM count, NLR, MLR, and SII (p < 0.05). Conclusion: The differences in these markers were stable and cannot be eliminated by a full course of treatment. This study provides impetus for the inflammatory hypothesis of schizophrenia.