Data of patients of either sex, aged ≥18 years, who were either newly diagnosed cases of major depressive disorder or who were off anti-depression treatment for at least three months (or five half-lives) from full-text English articles, either interventional or observational, with evidence on the effect of four major SSRIs, escitalopram, sertraline, fluoxetine, and paroxetine, on serum levels of IL-6 and/or TNF-α and/or CRP from the PubMed database were included. This evidence concerns the gene IL6 and depressive disorder.