BDNF and major depressive disorder: Thus, most of the originally discovered roles of this neurotrophin shape the cellular and functional organization of the normal brain, but more recent findings have converged to demonstrate that dysregulation of BDNF is implicated in a range of neurological disorders, including Alzheimer’s disease [4,5], Parkinson’s disease [6], Huntington’s disease [7,8], and amyotrophic lateral sclerosis (ALS) [9,10] and that low BDNF levels are associated with depression [11] and anxiety [12].