Nevertheless, the MDD patients showed no statistically significant difference in IL-6 and TNF concentration compared with HCs (901.03 ± 617.92 pg/ml vs 707.31 ± 584.07 pg/ml, P = 0.265; 514.12 ± 194.41 pg/ml vs. 414.87 ± 288.36 pg/ml, P = 0.166, respectively, Fig. 4). Here, IL6 is linked to major depressive disorder.