IFNG and major depressive disorder: A significant group × time interaction was found for CES-D (Center for Epidemiologic studies Depression Scale) score (p = 0.01), the TRP/LNAA (tryptophan/large neutral amino acid) ratio (p = 0.04), the composite score of pro-inflammatory cytokines (p = 0.04), IL-1β (interleukin-1 beta) (p = 0.04), and IFN-γ (interferon gamma) (p = 0.03).