Specifically, the human BDNF polymorphism that converts the 66 position amino acid valine to a methionine (Val66Met) has been associated not only with mental illness risk, but also with memory (Egan et al., 2003; Hariri et al., 2003; Hashimoto et al., 2008; van Wingen et al., 2010). Here, BDNF is linked to psychiatric disorder.