BDNF and major depressive disorder: The proposed mechanisms for the antidepressant action of exercise are predominantly connected to increased BDNF content in the hippocampus (Bjørnebekk et al., 2005) that may account for enhanced neurogenesis and diminished clinical manifestations of depression (Leite et al., 2012), with a significant role of β-endorphins (Dinas et al., 2011).