The human BDNF Val66Met gene polymorphism is the most widely studied variation with a single nucleotide polymorphism (SNP) at nucleotide 196 leading to a substitution of methionine (Met) for valine (Val) at codon 66, Val66Met, which interferes with BDNF trafficking, sorting, and secretion, and is associated with cognitive deficits (Egan et al., 2003; Chen et al., 2008; Chiaruttini et al., 2009; Nowacka and Obuchowicz, 2013). The gene discussed is BDNF; the disease is Cognitive impairment.