TNF and major depressive disorder: The result of a recent meta-analysis [12] demonstrated a significant increase in the levels of IL-17, IL-23, IL-6, TNF-α, soluble IL-2 receptor (sIL-2R), and IL-1 receptor antagonist (IL-1RA) in acutely ill patients with major depressive disorder (MDD), schizophrenia, and bipolar mania compared with controls (P < 0.01).