IFNG and major depressive disorder: For example, the levels of some cytokines, such as IL-1β, TNF-α, IL-6, and IFN-γ, appear to correlate with the depressive symptom severity or the presence of suicidality based on Hamilton’s depression rating scale (HDRS), the Lethality Suicide Attempt Rating Scale (LSARS), and the Risk-Rescue Rating (RRR) [121,122].