Among type 2 diabetes subjects, multiple stepwise regression analysis revealed that when BDNF Val/Met genotypes against depression scores, gender, BMI, HbA1c, BUN, Cr and numbers of complications, were independently correlated with depression scores (OR = 1.952, p < 0.05) and HbA1c (OR = 1.786, p < 0.05), indicating that the Met allele contributed to both the risk of development depression and diabetes. Here, BDNF is linked to major depressive disorder.