After adjusting for age, gender, race, BMI, educational level, smoking status, alcohol consumption, albumin, ALT, AST, creatinine, LDH, Uric acid, hypertension and physical activities, as blood urea nitrogen increased, the risk of depression was significantly reduced in the group without T2D (OR: 0.89, 95% Cl: 0.85-0.93; P < 0.001), meanwhile, it was not significant in the T2D group (OR: 1.00, 95% Cl: 0.95-1.05; P = 0.940). This evidence concerns the gene GPT and major depressive disorder.