NPY and major depressive disorder: Neuropeptide Y is one of the most abundant neuropeptides in the central nervous system and regulates the stress response and emotional behaviors (Morales-Medina et al., 2010; McGuire et al., 2011; Mickey et al., 2011; Kormos and Gaszner, 2013) and has been suggested to be involved in anxiety, depression and posttraumatic stress disorder (PTSD) (Sah et al., 2009; Sah and Geracioti, 2013; Enman et al., 2015).