Previous studies have demonstrated significant allelic association between the risk for AD and both GABRA2 and GABRB1 polymorphisms in humans (Parsian and Zhang, 1999; Sun et al., 1999; Porjesz et al., 2002; Song et al., 2003; Edenberg et al., 2004, 2005). The gene discussed is GABRA2; the disease is Alzheimer disease.