BDNF and depressive disorder: In particular, the neurotrophic hypothesis of depression posits that decreased cell support mediated by the brain-derived neurotrophic factor (BDNF) and its tyrosine-protein kinase B (trkB) receptor leads to decreased neurogenesis, neuronal atrophy, and glial cell loss in the hippocampus (HC) and that the BNDF deficit is blocked or reversed by antidepressant drug treatment [7,8].