An association between inflammation and behavioral domains of mental disorders is of growing interest. Recent studies reported an association between aggression and inflammation. In this study, we investigated the association between aggressive behavior and inflammatory markers in schizophrenia inpatients.

Adult schizophrenia inpatients without affective symptoms (n=213) were retrospectively identified and categorized according to their C-reactive protein measurement at admission as either elevated (CRP>1mg/dL; n=57) or normal (CRP<1mg/dL; n=156). The following indicators of aggression were compared: PANSS excitement component (PANSS-EC), restraints and suicidal behavior during hospitalization. Univariate comparisons between elevated and normal CRP levels were performed and multivariate analysis was conducted to control for relevant covariates.

CRP levels significantly correlated with other laboratory markers indicating increased inflammation including leukocyte count and neutrophil to lymphocyte ratio (r=0.387, P<0.0001 and r=0.356, P<0.0001) respectively. Inpatients with elevated C-reactive protein displayed increased aggressive behavior compared to patients with normal CRP levels (<1mg/dL). This was manifested by higher rates of restraint during hospitalization (χ²=5.22, P=0.031) and increased PANSS-EC score (U=5410.5, P=0.012). Elevated CRP levels were not associated with suicidal behavior. Multivariate analysis revealed that higher PANSS-EC score was associated with elevated CRP after controlling for the covariates age, sex, BMI and smoking.

This study identified a potential biological correlate (inflammation) of a specific behavioral endophenotype (aggression) in schizophrenia inpatients.