IL6 and depressive symptom measurement: Some of the inflammatory markers are considered as to be (potentially) significant for depression, e.g., the pro-inflammatory cytokines as interleukin-6 (IL-6), interleukin-1 (IL-1), and tumor necrosis factor (TNF-α), as well as the acute phase reactant protein C-reactive protein (CRP) [23,24,25].