BDNF and major depressive disorder: Among these models, chronic unpredictable stress (CUS) produces anxiety and depression-like behaviors and cognitive impairment, which are accompanied by reduced levels of neurotrophins (i.e., BDNF and others important for neuronal survival), impaired hippocampal neurogenesis and dendritic arborization, and neuroinflammatory response (microgliosis and astrogliosis; Farooq et al., 2012; Campos et al., 2013b).