Interestingly, the long-term effect of ECT on IL-6 seems to correlate with outcome, providing further evidence of the mechanism of action of ECT and supporting the inflammation theory in MDD.
It is concluded that increased production of IL-6 and IL-1 in major depression may underlie both immune activation and the "acute" phase response in that illness, and that disorders in Hp may be related to the pathophysiology and pathogenesis of major depression.
Meta-analyses of the two samples presented evidence for interaction with rs1818879 (IL6) (RD=0.059, SE=0.016, p<0.001), with the replication Münster sample approaching statistical significance in analyses restricted to recurrent MDD and controls following correction for multiple testing (q=0.066).
Moreover, logistic regression analyses correctly classified BD and MDD patients with 98.1% accuracy, using a combination of IL-6, IL-8, ST2, sTNFR2 (directly associated with BD) and IL-12 and TNF-α (directly associated with MDD).
No correlations existed between plasma IL-6 levels and plasma catecholamine metabolite levels in patients with MDD, and the severity of depressive state was related to plasma IL-6 levels in MDD.
Our results show that patients with MDD without other comorbidities (N = 33) exhibited significantly higher levels of pro-inflammatory IL-12 and IL-6 in plasma and that these cytokines were associated with increased numbers of non-classical (CD11b<sup>+</sup>CD16<sup>bright</sup>CD14<sup>neg</sup>) monocytes and increased activation state (CD40<sup>+</sup>CD86<sup>+</sup>) of classical monocytes in circulation.
Peripheral levels of interleukin-6 (IL-6), tumor necrosis factor (TNF)-alpha, IL-10, the soluble IL-2 receptor, C-C chemokine ligand 2, IL-13, IL-18, IL-12, the IL-1 receptor antagonist, and the soluble TNF receptor 2 were elevated in patients with MDD compared to HCs, whereas interferon-gamma levels were lower in MDD (Hedge's g = -0.477, P = 0.043).
Plasma mtDNA concentration was measured with real-time quantitative PCR targeting two regions of the mtDNA and plasma levels of four cytokines (GM-CSF, IL-2, IL-4, and IL-6) were measured with a multiplex immunoassay method in 109 patients with major depressive disorder (MDD).
Pre-treatment leptin showed a significant clinical correlation with reduction of panic symptoms in MDD patients at visit 5 (p=0.011), whereas pre-treatment IL-6 showed a negative correlation with panic symptom reduction in PD patients (p=0.022).
Significantly higher inflammatory biomarkers such as the high sensitivity C-reaktive protein (hsCRP) and proinflammatory acute phase cytokines interleukine-1β (IL-1β) and interleukine-6 (IL-6) underlined the higher cardiovascular risk in physically healthy MDD patients.
Therefore, we assessed these variables in a group of patients with major depressive disorder (MDD) and measured levels of the pro-inflammatory cytokine IL-6 and the anti-inflammatory cytokine IL-10.
These results suggest that the plasma levels of IL-6 reflect the severity of MDD and that plasma IL-6 levels might be another biological-state marker for the depressive state.