IL6 and depressive symptom measurement: Indices of inflammation [e.g., circulating levels of cytokines (e.g., interleukin-6 (IL-6) and acute phase proteins (e.g., C-reactive protein (CRP)] are elevated in individuals with depression compared to controls (14) and inflammatory biomarkers have been linked to specific aspects of depression, such as anhedonia and negative affect (15–17).