As shown in Figure 4B, the combined indicator of baseline BDNF and S100B was able to differentiate OA participants in the trans-MDD group from the non-MDD group with the AUC value of 0.806 (95% CI: 0.703∼0.885; specificity: 69.23%; sensitivity: 85.71%), which was better than single baseline BDNF (AUC = 0.644; 95% CI: 0.530∼0.747) or baseline S100B (AUC = 0.777; 95% CI: 0.670∼0.862). This evidence concerns the gene BDNF and major depressive disorder.