Moreover, multiple studies have shown that BDNF is both necessary and sufficient for anti-depressant drug action (Banasr and Duman, 2008; Castren and Rantamaki, 2010; Duman and Monteggia, 2006; Schmidt et al., 2008; Yu and Chen, 2011), which leads to the interesting possibility that BDNF-mediated regulation of Wnt2 expression may be an important mechanistic link in the alleviation of symptoms during depression. This evidence concerns the gene BDNF and major depressive disorder.