IL6 and depressive disorder: A meta-analysis involving 22 studies (20,791 participants) found significant associations between concurrent depression and C-reactive protein (CRP) [n = 7; correlation coefficient r = 0.12; 95% confidence interval (CI) = 0.04 to 0.19] as well as interleukin-6 (IL-6) (n = 7; r = 0.17; 95% CI = 0.10 to 0.24).