TNF and depressive disorder: Increased pro-inflammatory markers [IL-6, IL-1β, TNF-α, and C-reactive protein (CRP)] occur in individuals with depression (Laske et al., 2008; Steiner et al., 2012), supported by reports of anti-depressant effects of TNF-α antagonists (Soczynska et al., 2009; Fond et al., 2014; Abbott et al., 2015).