BDNF and major depressive disorder: Neurotrophins, particularly the brain-derived neuronal growth factor (BDNF) [21,22], are also thought to play a pivotal role in the pathophysiology of depression; a reduction of the BDNF-related trophic support, indeed, seems to entail neuronal and glial atrophy in brain areas involved in the disorder (hippocampus, amygdala, prefrontal cortex) [23].