BDNF and major depressive disorder: The antidepressant effect via BDNF has important roles in supporting neuronal survival and maintaining neuroplasticity.45 In rodent models of stress-induced depression, lower levels of BDNF in the hippocampus were restored by antidepressant treatment.44, 46 Furthermore, antidepressant treatments have failed to elevate hippocampal neurogenesis at the subgranular zone in a mouse model of absence of BDNF–tyrosine receptor kinase B (BDNF-TrkB) signalling.47 Consequently, neurotropic factors, such as BDNF, may have an important role in the mechanism of antidepressant action.