BDNF and major depressive disorder: Functional polymorphisms of the BDNF gene have been investigated in AD, PD, schizophrenia, depression patients, such as rs2030324, rs2049045, rs6265, rs2203877, rs7103411, rs988748, rs6265 [G196A], rs56164415[C270T], rs16917204 [G11757C], rs13306221 [G-712A] (Kunugi et al., 2001; Parsian et al., 2004; Bodner et al., 2005; Vepsäläinen, 2005; Dmitrzak-Weglarz et al., 2008; Borroni et al., 2009; Zdanys et al., 2009; Su et al., 2011; Zhang et al., 2011).