IFNG and major depressive disorder: Key to the interplay between inflammation and MDD, IFN-γ, previously mentioned for its marked elevation in MDD, is known to inhibit the PI3K and Akt pathway and activate NF-κB, STAT3, and GSK-3, leading to a positive feedback loop, as Th1 and Th17 cells, both of which are stimulated by GSK-3, also induce the production of IFN-γ [46,73,91].