IL6 and major depressive disorder: Depression is often characterized by a persisting state of neuroinflammation, accompanied by elevated blood concentrations of pro-inflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and some acute phase proteins, like C-reactive protein (CRP) (Howren et al., 2009; Kim and Won, 2017; Maeng and Hong, 2019; Munshi et al., 2020).