IL6 and major depressive disorder: However, the contradictions in that study are that the IL-6 level in patients with MDD was too much higher than that in most studies, both before and after treatment (week 0: 134 ± 53 pg./mL; week 8: 106 ± 34 pg./mL), and it failed to match the IL-6 ELISA kit range which is 0.1 to 10 pg./mL.