The key pathophysiological processes of AD include decreased functional brain activity and connectivity (Dennis and Thompson, 2014), reduced serotonergic neurotransmission (Smith et al., 2017; Mecca, 2019) associated with neuropsychiatric symptoms (Butzlaff and Ponimaskin, 2016; Chakraborty et al., 2019), neuroinflammation, (Kinney et al., 2018) and alteration of key signaling pathways (i.e., BDNF) (Peng et al., 2005; Tanila, 2017). This evidence concerns the gene BDNF and Alzheimer disease.