Inflammatory markers in depression: A meta-analysis of mean differences and variability in 5,166 patients and 5,083 controls

The magnitude and variability of cytokine alterations in depression are not clear.

To perform an up to date meta-analysis of mean differences of immune markers in depression, and to quantify and test for evidence of heterogeneity in immune markers in depression by conducting a meta-analysis of variability to ascertain whether only a sub-group of patients with depression show evidence of inflammation. DATA SOURCES: Studies that reported immune marker levels in peripheral blood in patients with depression and matched healthy controls in the MEDLINE database from inception to August 29th 2018 were examined. STUDY SELECTION: Case-control studies that reported immune marker levels in peripheral blood in patients with depression and healthy controls were selected. DATA EXTRACTION AND SYNTHESIS: Means and variances (SDs) were extracted for each measure to calculate effect sizes, which were combined using multivariate meta-analysis. MAIN OUTCOMES AND MEASURES: Hedges g was used to quantify mean differences. Relative variability of immune marker measurements in patients compared with control groups as indexed by the coefficient of variation ratio (CVR).