Results from the Collaborative Study on the Genetics of Alcoholism demonstrated highly significant associations between alcohol dependence and single nucleotide polymorphisms (SNPs) in GABRA2 (Edenberg et al. 2004). Numerous studies have replicated these associations with GABRA2 and alcohol dependence (Covault et al. 2004; Lappalainen et al. 2005; Fehr et al. 2006; Drgon et al. 2006; Soyka et al. 2008; Covault et al. 2008; Enoch et al. 2009; Bierut et al. 2010; Olfson and Bierut 2012; Philibert et al. 2009; Ittiwut et al. 2012; Villafuerte et al. 2011; Li et al. 2013), although one study has found this effect in the opposite direction (Lind et al. 2008). While these studies have primarily focused on adult alcohol dependence, two studies have examined variation in GABRA2 for adolescent alcohol dependence and CD. These studies found no association with GABRA2 and adolescent alcohol dependence, but found evidence for an association with CD in adolescents (Dick et al. 2006; Sakai et al. 2010). These results are not altogether surprising since estimates of heritability of alcohol dependence are roughly 64% in adulthood (Heath et al. 1997),
