Fifteen studies involving measurements of inflammatory proteins and level of depression in 1102 individuals with MS were included in the meta-analysis: five for interleukin (IL)-10 (LPS and PHA), four for tumour necrosis factor (TNF)-α, four for interferon (IFN)-γ, and four for IL-6 (LPS and PHA). This evidence concerns the gene IL10 and major depressive disorder.