Association between elevated C-reactive protein and manic polarity in acute psychiatric inpatients with affective symptomatology

The interplay between the immune system and behaviour is of increasing interest in psychiatry research. Specifically, accumulating data points to a link between inflammation and psychopathology, including affective symptomatology. We investigated the association between inflammation and affective polarity in psychiatric inpatients who were hospitalized due to an affective exacerbation. Data was collected retrospectively and comparisons were made between manic and depressed patients. C-reactive protein (CRP), a general laboratory marker of immune activation and inflammation, was used as a non-specific inflammatory biomarker. Age, smoking and body mass index were considered covariates. Manic polarity (n = 89) was associated with statistically significant elevated CRP levels compared to depressed polarity (n = 44, 56%; p = 0.036), after controlling for covariates. No differences were observed in CRP levels across Diagnostic and Statistical Manual of Mental Disorders-IV Edition-Text Revised psychiatric diagnoses. These findings suggest a transdiagnostic association between inflammation and manic polarity in affective inpatients.