TNF and major depressive disorder: Mounting evidence suggests that chronic inflammatory activity is strongly associated with an increased risk of developing major depression through mechanisms such as increased peripheral immune action, continuous production of proinflammatory regulators interleukin‐1 (IL‐1β), tumor necrosis factor (TNF), and interleukin‐6 (IL‐6) by microglia in the brain, and reduced production of anti‐inflammatory factors (Dilger & Johnson, 2008).