VEGFA and major depressive disorder: Further research has confirmed that the up-regulation of VEGF levels induced by the activation of astrocytes in MDD patients significantly increases the permeability of the BBB, which enables more pro-inflammatory cytokines to enter the brain, fuel neuroinflammation in the human brain, and leads to depressive-like behaviors (Argaw et al., 2009; Dudek et al., 2020).