BDNF and major depressive disorder: Given its trophic effects on neurons and its central role in high-order cognitive functions, BDNF has rapidly emerged as a key element in the pathophysiology of numerous brain disorders, including neurological disorders [e.g. epileptogenesis [9]], neurodegenerative diseases [e.g. amyotrophic lateral sclerosis [10], Huntington [11], Alzheimer's and Parkinson's diseases [12]] and psychiatric disorders [e.g. anxiety/depression [13], [14], addiction [15] and schizophrenic psychosis [16]].