IL7 and major depressive disorder: Serum levels of IL-7, IL-9, IL-17A, and VEGF were significantly higher in adolescents with MDD at W0 compared with those in HVs (IL-7: F = 23.97; IL-9: F = 8.44; IL-17A: F = 13.10; and VEGF: F = 21.79; in all cases df = 80.3 and P < 0.0001).