Indeed, chronic stress has been described to decrease the BDNF blood level among MDD patients (Molendijk et al., 2011; Kreinin et al., 2015) as well as its expression in the hippocampal dentate gyrus of post-mortem brains of MDD subjects (Castrén and Rantamäki, 2010). Here, BDNF is linked to major depressive disorder.