BDNF and major depressive disorder: Additionally, given the critical importance of growth factor support and deficiencies thereof in the pathophysiology of depression, we further aimed to investigate whether Cry2-deficiency affects expression of the vascular endothelial growth factor (VEGF) and of the brain derived neurotrophic factor (BDNF), which have been both associated to depressive disorders (as reviewed in Yu and Chen 2011; Clark-Raymond and Halaris 2013).