Patients suffering from depression often display increased levels of pro-inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) [25, 26], as well as endogenous metabolites including nesfatin-1 and corticosterone [27]. This evidence concerns the gene IL6 and major depressive disorder.