We, therefore, carried out this study aimed at investigating differences in BDNF and cortisol plasmatic levels in patients diagnosed with CUD-primary-MDD and CUD-induced-MDD and also to compare them with a sample of MDD patients (without cocaine use), a sample of CUD (without MDD), and a group of healthy controls (HC) before and after a stress challenge. Here, BDNF is linked to major depressive disorder.