TNF and major depressive disorder: Cytokines refer to a series of small heterogeneous peptides which can affect cell proliferation and differentiation as well as inflammation, as evidenced by studies that the study of these cytokines is important for psychiatric disorders like depression and anxiety [113], of which IL-1β has been implicated in the etiology of depressive-like behaviors, and in conjunction with IL-6 and TNF, affects depressive disorders [114].