Multiple studies have documented a disparity in the levels of pro-inflammatory cytokines, including interleukin (IL) −1, IL-6, IL-8, IL-12, and tumour necrosis factor α (TNF-α), and the levels of anti-inflammatory cytokines, such as transforming growth factor-beta (TGF-β) and IL-10, in individuals diagnosed with depression.77 Here, IL6 is linked to major depressive disorder.