Psy-World

A meta-analysis confirms the association between elevation of cytokines and major depression.

Many studies have suggested that major depression is accompanied by immune dysregulation with increased production of proinflammatory cytokines. However, the association between activation of the inflammatory response system (IRS) and depression, documented in individual studies of various cytokines, is not consistently significant in all studies or for all cytokines. Thus, a meta-analysis was conducted to measure the concentrations of specific cytokines in patients with a major depressive episode and control subjects. Of a total of 136 studies identified for review, 24 cross-sectional studies satisfied inclusion and exclusion criteria, 16 studies for interleukin (IL)-6, 13 for tumor necrosis factor (TNF)-α, 9 for IL-1β , 5 for IL-2, 5 for IL-4, 4 for interferon (IFN)-γ, 4 for IL-8, and 6 for IL-10. Higher concentrations of TNF-α, with weighted mean difference (WMD) of 3.97 pg/mL, were found in depressed subjects compared with control subjects (438 depressed/350 nondepressed) (p < 0.00001). IL-6 concentrations were also higher in depressed subjects compared with control subjects (492 depressed/400 non-depressed) (p < 0.00001) with an overall WMD of 1.78 pg/mL. No significant differences for the other cytokines studied were found among depressed and non-depressed subjects. These results strengthen the evidence that depression is associated with activation of the IRS. Whether the presence of the two proinflammatory cytokines, TNF-α and IL-6, may be a cause or consequence of major depression remains to be identified. Dowlati Y, Herrmann N, Swardfager W, Liu H, Sham L, Reim EK, Lanctôt KL (2010). A Meta-Analysis of Cytokines in Major Depression. Biol Psychiatry 67:446-457. Updated February 2010