Inflammatory markers in depression: A meta-analysis of mean differences and variability in 5,166 patients and 5,083 controls.
Level 4 - case-series / case-control
Meta-analysis of observational case-control studies
PubMed 32113908 · doi:10.1016/j.bbi.2020.02.010
What was done
Systematic review and multivariate meta-analysis of case-control studies indexed in MEDLINE up to August 29, 2018. The study evaluated mean differences (Hedges' g) and relative variability (coefficient of variation ratio, CVR) of peripheral blood immune markers between patients with depression and matched healthy controls across 107 studies comprising 5,166 patients and 5,083 controls.
What was found
Peripheral blood levels of several inflammatory markers were significantly higher in patients with depression: - CRP: g = 0.71 (95% CI: 0.50–0.92; p < 0.0001) - IL-3: g = 0.60 (95% CI: 0.31–0.89; p < 0.0001) - IL-6: g = 0.61 (95% CI: 0.39–0.82; p < 0.0001) - IL-12: g = 1.18 (95% CI: 0.74–1.62; p < 0.0001) - IL-18: g = 1.97 (95% CI: 1.00–2.95; p < 0.0001) - sIL-2R: g = 0.71 (95% CI: 0.44–0.98; p < 0.0001) - TNFα: g = 0.54 (95% CI: 0.32–0.76; p < 0.0001) Relative variability (CVR) was significantly lower in patients with depression for CRP (CVR = 0.85; 95% CI: 0.75–0.98; p = 0.02), IL-12 (CVR = 0.61; 95% CI: 0.46–0.80; p < 0.01), and sIL-2R (CVR = 0.85; 95% CI: 0.73–0.99; p = 0.04), while unchanged for IL-3, IL-6, IL-18, and TNFα.
Why it matters
Elevated inflammatory markers accompanied by equal or reduced variability suggest that systemic inflammation in depression reflects a general rightward shift in the immune profile rather than a phenomenon limited to a distinct inflamed subgroup.
Limits
All included data derive from observational case-control designs, precluding causal inference. Peripheral blood measures may not reflect central neuroinflammation. Potential residual confounding from somatic health, medication, or lifestyle factors cannot be fully excluded based on abstract data alone.
Cited by
- supports Depressed individuals show elevated levels of inflammatory markers like cytokines compared to healthy controls.