IFNG and major depressive disorder: Earlier studies in patients with human immunodeficiency virus (HIV) infection and in cancer patients have shown that activation of IFN-γ mediated pathways is related to fatigue, depression, immunodeficiency, and an impaired quality of life.20, , , -24 IFN-γ has a central function in the metabolic reprogramming of immune cells and also other responsive cells, causing far-reaching signal changes that have effects far beyond immunological processes.