To date, a few genes have been shown to be associated with AD, including ADH1B,ALDH2, ADH4, CHRNA5, CHRM2, GABRA2, and GABRG1 (Agrawal et al., 2012; Covault et al., 2008; Edenberg et al., 2004; Edenberg and Foroud, 2006; Edenberg et al., 2006; Enoch, 2008; Enoch et al., 2009; Luo et al., 2005; Wang et al., 2009; Wang et al., 2004); however, the variation in each of these genes accounts for only a small portion of the vulnerability to AD. This could be due to the study design, the gene coverage, or most likely the complex etiology and heterogeneity of AD.
