Exacerbated inflammatory background [37,38], unbalanced oxidant–antioxidant status [39], decreased neurotrophin levels [40,41,42], impairments in neurotransmitter systems [43], and elevated levels of neurofibrillary tangles (NFTs) [44,45] appear as common ground for AD and depression, while the co-occurrence of AD and anxiety is consistent with elevated Aβ build-up [46,47] and extensive NFTs burden [48]. Here, BDNF is linked to Alzheimer disease.