IL6 and major depressive disorder: Compared to the CTL group, the MDD group displayed a significant increase in IL-6 and TNF-α (P < 0.01 for Figure 4); the levels of IL-6 and TNF-α in the MDS group were significantly decreased after administering SA4503 during CUMS (P < 0.01), while the level of IL-1 was not statistically significant between the four groups.