In this study of outpatients with depressive disorders without a bipolar diagnosis, summations of multiple serum biomarker scores relating to cortisol, IL-1β, homocysteine, total cholesterol, and folate predicted increased suicidal severity, and summed scores relating to cortisol, total cholesterol, and folate predicted fatal/non-fatal suicide attempt during the 12-month pharmacotherapy, respectively, in a dose-dependent manner. Here, IL1B is linked to depressive disorder.