Pro-inflammatory markers and fatigue in patients with depression: A case-control study

The aim of this work was to investigate differences between depressed subjects (PG) and non-depressed healthy control participants (HCG) with regard to fatigue dimensions and inflammation. For this purpose, 43 participants in the PG and 51 participants in the HCG were included in the study. IL-6, IL-1β, TNF-α, IFN-γ, and CRP were assessed in venous blood samples. Fatigue and depression were assessed using the FIS-D and BDI-FS questionnaires. Main results showed higher BDI-FS values in PG. Moreover, PG showed mean differences for fatigue dimensions when compared to the HCG. For the pro-inflammatory markers, a moderate group effect was found between PG and HCG which was mainly caused by IL-6. Correlations between TNF-α and BDI-FS, TNF-α and cognitive fatigue, TNF-α and psychosocial fatigue were found within the PG. In the HCG, correlations were found between IL-6, TNF-α and somatic fatigue, as well as IL-6 and cognitive fatigue. Significant correlations were found between the psychological variables in both groups. All results were controlled for the confounding variables gender, age, BMI and multiple comparisons. These results suggest the presence of inflammation in both depression and fatigue. However, each correlates with different pro-inflammatory parameters, suggesting a biological heterogeneity.