COMPARISON OF INFLAMMATORY AND METABOLIC PARAMETERS IN UNIPOLAR AND BIPOLAR DEPRESSION

Abstract

Objective: Differentiating bipolar depression (BPD) from unipolar depression (UPD) remains a clinical challenge. This study aimed to compare inflammatory and metabolic parameters among hospitalized patients with UPD, BPD, and bipolar mania (BPM), and to evaluate potential biological differences between UPD and BPD.Material and Methods: This retrospective study included 399 inpatients diagnosed with Depressive Episode (F32) or Bipolar Disorder (F31) according to ICD-10 criteria at a tertiary university hospital. Hematological, inflammatory (white blood cell count, neutrophil count, C-reactive protein, ferritin), and metabolic parameters [fasting glucose, lipid profile, Triglycerides (TyG) index] were retrospectively analyzed. Group comparisons were performed using appropriate parametric and non-parametric tests. Analyses of covariance (ANCOVA) were conducted to adjust for age, sex, and number of hospitalizations.Results: Neutrophil counts and TyG index values were significantly higher in the BPD group compared with the UPD group. Significant differences in metabolic parameters were observed across the three groups, with a less favorable metabolic profile particularly evident in BPD. After adjustment for age, sex, and hospitalization frequency, neutrophil counts and several metabolic parameters remained significantly different between groups, whereas other inflammatory markers were not consistently associated with diagnostic group. Ferritin levels did not differ significantly between groups.Conclusion: These findings suggest biological heterogeneity between unipolar and BPD in terms of inflammatory and metabolic characteristics. However, given the substantial overlap between groups, these parameters should be interpreted as supportive biological correlates rather than diagnostic markers.