IL6 and major depressive disorder: In particular, a large meta-analysis reported increased levels of interleukin-6 (IL-6), tumor necrosis factor (TNF)-alpha, IL-10, soluble IL-2 receptor, C-C chemokine ligand 2, IL-13, IL-18, IL-12, IL-1 receptor antagonist, and soluble TNF receptor 2 in MDD patients compared to healthy controls9.