BDNF and depressive symptom measurement: Previous studies have reported that mice with deficiency in BDNF demonstrated depression-like behaviors, and administration of BDNF produced antidepressant effects (Nawa et al., 1994; Karege et al., 2002; Shimizu et al., 2003; Karege et al., 2005; Brunoni et al., 2008; Hammack et al., 2009; B. H. Lee and Kim, 2010), indicating BDNF correlates with development of depression.