BDNF and major depressive disorder: Brain derived neurotrophic factor (BDNF) plays key roles in several neurodevelopmental and neuropsychiatric disorders including Rett Syndrome (Chang et al., 2006; Li and Pozzo-Miller, 2014), schizophrenia (Durany and Thome, 2004; Lu and Martinowich, 2008), major depression disorder (MDD; Martinowich et al., 2007), attention deficit hyperactivity disorder (ADHD; Kebir et al., 2009; Caylak, 2012), and actions of pharmacological treatments (Longo and Massa, 2013; Ninan, 2014) in these diseases.