This argument was further confirmed by the ROC curve and R analytics, with AUC (95%CI) = 0.8770 (0.8281-0.9260) for IL-18 to predict prognosis and a positive correlation between pretreatment IL-18 levels and BDI scores in depressed subjects (r = 0.781, P < 0.001); that is, the higher the IL-18 level, the more likely the patients are to have concurrent depression. This evidence concerns the gene IL18 and major depressive disorder.