In addition to the regulation of striatal neuron differentiation, corticostriatal BDNF signaling has been implicated in the etiology and treatment of neurodegenerative and neuropsychiatric disorders including drug addiction [48], depression [49], [50], schizophrenia [51], and Huntington's disease (HD) [52], [53], [54], [55]. Here, BDNF is linked to major depressive disorder.