New perspectives have emerged regarding the processes associated with depressive disorders and their many comorbid conditions. Particular attention has been paid to the potential role of inflammatory factors in promoting these illnesses. These inflammatory responses include those elicited by pathogenic stimuli, as well as sterile inflammatory processes, such as those related to severe or chronic stress. These diverse challenges may activate common processes in which cytokines, which are inflammatory signaling molecules, provoke the dysregulation of several growth factors, including brain-derived neurotrophic factor, fibroblast growth factor-2, macrophage migration inhibitory factor, and erythropoietin. The result of such dysregulation favors the development of depressive disorders and their comorbid illnesses, such as heart disease, diabetes, autoimmune conditions, and poststroke depression.