NUCB2 and major depressive disorder: Based on the ROC curve analysis, plasma nesfatin-1 cut-off point of 20.25 ng/mL showed 82.4% sensitivity and 91.3% specificity, and with the Area Under Curve (AUC) 0.903 (95% CI 0.835–0.971) was the optimal cut-off point for identification of severe depression (Fig. 4).