M1-polarized microglia are usually induced by proinflammatory stimuli and adopt a proinflammatory state that produces proinflammatory cytokines, such as tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6(IL-6), nitric oxide (NO), and reactive oxygen species (ROS), which are consistently upregulated in depression patients [8, 9]. Here, IL6 is linked to major depressive disorder.