Cytokines and late-life depression.

Cytokines are peripherally and centrally produced proteins that regulate immune and immunological responses. They also have neurochemical, neuroendocrine and behavioural effects similar to those seen in patients with depression. A review of the literature reveals several cytokines, including IL-1beta, IL-2, IL-6 and IFN, have been shown to be elevated in plasma of working-age adults with depression and dysthymia. A more detailed review of the literature also reveals similar associations between cytokines and late-life depression, with IL-1beta, IL-6 and TNF-alpha all being reported to be elevated in both depression and dysthymia. It has been hypothesized that cytokines provide the link between depression, neurochemical changes and the altered HPA axis that are known to occur in this disease, and evidence is presented that supports this view. However, the evidence that antidepressants may have effects on cytokines is conflicting. Increased cytokine levels may also serve as an explanation for the increased risk for vascular disease that has been associated with depression, and a possible mechanism for this is discussed.