TNF and major depressive disorder: However, using a larger cohort of IFN-α treated HCV patients (from which we have selected all serum samples used in the present study) we have found no differences at TW0 in the levels of key inflammatory cytokines, including IL-1β, IL-6, IL-17 and TNF-α, between those who later develop or do not develop depression (although, interestingly, we found differences in the prediction of fatigue) (Hepgul et al., 2016, Russell et al., 2019).