Mounting evidence suggests that aberrations in immune-inflammatory pathways contribute to the pathophysiology of
major depressive disorder (MDD), and individuals with MDD may have elevated levels of predominantly pro-inflammatory
cytokines and
C-reactive protein. In addition, previous meta-analyses suggest that
antidepressant drug treatment may decrease peripheral levels of
interleukin-1 beta (IL-1β) and
IL-6. Recently, several new studies examining the effect of
antidepressants on these
cytokines have been published, and so we performed an updated meta-analysis of studies that measured peripheral levels of
cytokines and
chemokines during
antidepressant treatment in patients with MDD. The PubMed/MEDLINE, EMBASE, and PsycInfo databases were searched from inception through March 9, 2017. Forty-five studies met inclusion criteria (N = 1517). Peripheral levels of
IL-6,
tumor necrosis factor-alpha (TNF-α), IL-1β,
IL-10,
IL-2,
IL-4,
interferon-γ,
IL-8, the C-C motif
ligand 2
chemokine (CCL-2), CCL-3,
IL-1 receptor antagonist,
IL-13,
IL-17,
IL-5,
IL-7, and the soluble
IL-2 receptor were measured in at least three datasets and thus were meta-analyzed.
Antidepressant treatment significantly decreased peripheral levels of
IL-6 (Hedges g = -0.454, P <0.001), TNF-α (g = -0.202, P = 0.015),
IL-10 (g = -0.566, P = 0.012), and CCL-2 (g = -1.502, P = 0.006). These findings indicate that
antidepressants decrease several markers of peripheral
inflammation. However, this meta-analysis did not provide evidence that reductions in peripheral
inflammation are associated with
antidepressant treatment response although few studies provided separate data for treatment responders and non-responders.