IL6 and major depressive disorder: When stratifying the analysis by sex, IL-6 was still significantly increased in male patients with MDD ([n = 11] 1.46 pg/mL, IQR 1.17–4.68 pg/mL vs. the healthy male volunteers [n = 13] 0.85 pg/mL, IQR 0.72–1.25 pg/mL; P = 0.0029).