In particular, evidence suggests that depression is associated with increased circulating concentrations of proinflammatory cytokines such as IL-1β, IL-6, TNF-α, and IFN-γ in association with elevations in chemokines and the acute phase protein, CRP (Maes et al., 1995a; Lanquillon et al., 2000; Cizza et al., 2008; Simon et al., 2008; Diniz et al., 2010; Hughes et al., 2012). Here, TNF is linked to major depressive disorder.