When covariates of medication use (including both psychopharmaceuticals and birth control), BMI, and menstrual cycle were analyzed, the relationship between IL-6 and BDI-II scores remained significant, b ​= ​7.90, p = <.01, CI (2.74, 13.05), suggesting that the covariates did not account for a significant portion of the variance in depression scores explained by IL-6. Here, IL6 is linked to major depressive disorder.