BDNF and major depressive disorder: Duman and coworkers (1997) have shown that synthesis of BDNF was increased by antidepressant treatment, suggesting a deficiency in BDNF might contribute to depression-like behaviors (Duman and Monteggia, 2006). Emerging studies have indicated that BDNF plays a critical role in development of depression and antidepressant treatment (Nawa et al., 1994; Shimizu et al., 2003; Brunoni et al., 2008; Hammack et al., 2009; B. H. Lee and Kim, 2010).