Major depression occurs in 4.4% to 20% of the general population. Studies suggest
that major depression is accompanied by immune dysregulation and activation of the
inflammatory response system (IRS). Our objective was to quantitatively summarize
the data on concentrations of specific cytokines in patients diagnosed with a major
depressive episode and controls.
We performed a meta-analysis of studies measuring cytokine concentration in patients
with major depression, with a database search of the English literature (to August
2009) and a manual search of references.
Twenty-four studies involving unstimulated measurements of cytokines in patients meeting
DSM criteria for major depression were included in the meta-analysis; 13 for tumor
necrosis factor (TNF)-alpha, 9 for interleukin (IL)-1beta, 16 for IL-6, 5 for IL-4,
5 for IL-2, 4 for IL-8, 6 for IL-10, and 4 for interferon (IFN)-gamma. There were
significantly higher concentrations of TNF-alpha (p < .00001), weighted mean difference
(WMD) (95% confidence interval) 3.97 pg/mL (2.24 to 5.71), in depressed subjects compared
with control subjects (438 depressed/350 nondepressed). Also, IL-6 concentrations
were significantly higher (p < .00001) in depressed subjects compared with control
subjects (492 depressed/400 nondepressed) with an overall WMD of 1.78 pg/mL (1.23
to 2.33). There were no significant differences among depressed and nondepressed subjects
for the other cytokines studied.
This meta-analysis reports significantly higher concentrations of the proinflammatory
cytokines TNF-alpha and IL-6 in depressed subjects compared with control subjects.
While both positive and negative results have been reported in individual studies,
this meta-analytic result strengthens evidence that depression is accompanied by activation
of the IRS.
Copyright 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights