A recent meta-analysis of 82 studies, including 3,212 patients with depression and 2,798 HCs, showed that patients with depression had increased peripheral levels of IL-6, TNF-α, IL-10, soluble IL-2 receptor, chemokine ligand 2, IL-13, IL-18, IL-12, IL-1 receptor antagonist, and soluble TNF receptor 2, whereas interferon-gamma (IFN-γ) levels were decreased (3). Here, IL18 is linked to depressive symptom measurement.