Park et al. surveyed plasma levels of the eight cytokines at baseline and at 230 min, 1 day, and 3 days postketamine in MDD, and they found that ketamine treatment significantly increased IL-6 levels and reduced sTNFR1 levels at 230 min, but changes in cytokines were not associated with improvement in depression [44]. This evidence concerns the gene IL6 and depressive disorder.