BDNF and depressive disorder: Current studies have implicated that depression is not only viewed as abnormalities in the monoaminergic systems but is also involved in the impairment of neural plasticity, neurotrophic factors, and dendritic complexity in the hippocampus (Duman & Monteggia, 2006), and BDNF gene transcriptional activity can influence the neuronal growth, plasticity, and neurogenesis, which is conducive to the therapeutic response to antidepressants.