A meta-analysis of chemokines in major depression

• Chemokines are increasingly recognised as having a role in depression.
• Here we meta-analyse chemokines in major depression versus control.
• Significantly higher concentrations of MCP-1 were found.
• No significant differences in concentrations of IL-8 were found.
• There was significant heterogeneity across studies.

Chemokines are increasingly recognised as playing a role in depression. Here we meta-analyse the data on concentrations of all chemokines in patients diagnosed with a major depression versus healthy controls. We included studies which utilised Diagnostic and Statistical Manual (DSM)-IV diagnostic criteria for major depression, participants free from major medical conditions, studies with healthy controls, and unstimulated measurements of chemokines. We only included chemokines which had ≥ 3 studies performed. Two chemokines and 15 studies in total met criteria for this meta-analysis; 8 for Monocyte Chemotactic Protein (MCP)-1/CCL2 (n = 747), and 7 for Interleukin (IL)-8/CXCL8 (n = 560). There were significantly higher concentrations of CCL2/MCP-1 in depressed subjects compared with control subjects – overall mean difference of 36.43 pg/mL (95% CI: 2.43 to 70.42). There was significant heterogeneity across these studies (I2 = 98.5%). The estimates of mean difference between the control and depression groups did not remain significant when the trim-and-fill procedure was used to correct for publication bias. There was no significant difference in concentrations of IL-8/CXCL8 in depressed subjects compared with control subjects. Significant heterogeneity was found across these studies (I2 = 96.7%). The estimates of mean difference between the control and depression groups remained non-significant when the trim-and-fill procedure was used to correct for publication bias. This meta-analysis reports significantly heterogeneity in this field among studies. There are higher concentrations of the chemokine MCP-1/CCL2 in depressed subjects compared with control subjects, and no differences for IL-8/CXCL8. More high quality research and consistent methodologies are needed in this important area of enquiry.