Plasma levels of IL-6 and INF-γ and lipid profile, including total cholesterol (TC), triglycerides (TGs), low-density lipoproteins (LDLs), and high-density lipoproteins, were measured in 60 patients meeting criteria of the fifth version of the Diagnostic and Statistical Manual of Mental Disorders for Major Depression (22 patients who attempted suicide and 38 patients who did not attempt suicide) and 30 healthy controls.
Hormonal induction of tryptophan dioxygenase and the ability of hormones to potentiate IFN-gamma-induced activation of IDO might contribute to the development of inflammatory changes in major depressive disorder and in aging.