BDNF and Cognitive impairment: In neurodegenerative disorders (Weis et al., 2003; Blesch, 2006), including Alzheimer’s disease (AD; Lima Giacobbo et al., 2019; Ng et al., 2019) and mild cognitive impairment (MCI; Nagata et al., 2014), the levels of BDNF is one of the most common physiological changes.