A hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis has been found in the 50% of depressed patients (Krishnan and Nestler, 2008) and several evidences identify chronic stress, linked to an impairment of neurotrophins such as brain-derived neurotrophic factor (BDNF) and transforming-growth-factor-β1 (TGF-β1) (Caraci et al., 2018b), as a risk factor for the development of MDD (Pittenger and Duman, 2008; Caraci et al., 2010). Here, BDNF is linked to major depressive disorder.