IL6 and major depressive disorder: A recent meta‐analysis of large sample sizes with 2798 healthy controls and 3212 major depressive disorder (MDD) patients reveals the increased level of tumor necrosis factor (TNF), interleukin 6 (IL‐6), and IL‐10 in MDD patients, whereas interferon‐γ is reduced compared to healthy controls (Köhler et al., 2017).