TNF and major depressive disorder: Findings have shown that activation of microglia under pathological conditions leads to a decrease in neurogenesis (84) and the release of a large number of inflammatory factors, including interleukin-18 (IL-18), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), which exerted neurotoxic effects and cause depression and anxiety (85).