Additionally, a meta-analysis of 82 studies including 3,212 participants with MDD found that peripheral levels of IL-6, TNF-α, 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 were elevated in MDD patients compared to healthy controls (87). This evidence concerns the gene IL18 and major depressive disorder.