Elevated Serum Interleukin-23 and Interleukin-6 Levels in Schizophrenic Patients Compared to Those in Healthy Controls

Background: Various factors, including genetic, psychological, environmental, and immune dysfunction, may contribute to susceptibility to schizophrenia. Due to several reports regarding abnormal cytokine production, abnormal cytokine concentrations and their receptors in peripheral blood and cerebrospinal fluid, activation of the inflammatory response system, and altered levels of different cytokines in acute schizophrenia have been studied in recent years. Objectives: The purpose of this study was to examine interleukin-6 (IL-6) and IL-23 levels in schizophrenic patients versus those of healthy controls. Patients and Methods: In this case–control study, serum levels of IL-6 and IL-23 of 30 schizophrenic patients and 20 age- and gender-matched healthy controls were measured using an enzyme-linked immunosorbent assay (ELISA). The serum levels of these cytokines were measured in schizophrenic patients experiencing their first episode who had not taken any psychotic drugs for at least 2 months prior to the study. Statistical analysis was performed using SPSS software, version 17. IL levels showed a non-Gaussian distribution. The statistical analysis was performed using appropriate statistical tests, including the Kruskal-Wallis or Mann–Whitney test. Results: Serum IL-23 levels of schizophrenic patients were significantly higher (696 ± 132 pg/mL) than those of the control subjects (313 ± 33 pg/mL) (P = 0.007). Serum IL-6 levels of the schizophrenic patients were also significantly higher than those of the controls (5.28 ± 1.1 and 2.54 ± 0.32 pg/mL, respectively; P = 0.01). Conclusions: These findings indicate that immune system activation might be involved in the pathophysiology of schizophrenia.