Both adolescent MDD and adult MDD found abnormal expression of the following genes: PLEKHA7, SDR39U1, DIP2C, VEPH1, TBC1D14, ZNF839, SLC25A29, IPO7, RBM15, MAP2K5, PPM1D, and UBAC2, and some of their KEGG pathway information was found: nucleocytoplasmic transport, MAPK signaling pathway, gap junction, neurotrophin signaling pathway, oxytocin signaling pathway, fluid shear stress and atherosclerosis, p53 signaling pathway. The gene discussed is BDNF; the disease is major depressive disorder.