The 36 studies published between 1990 and 2011(Table 3), have yielded both positive and negative evidence of association across a variety of alcohol phenotypes. If more weight is placed on the recently published studies (Dick et al., 2004; Hack et al., 2011; Creemers et al., 2011; Schumann et al., 2011), which are presumably better powered to detect genetic association in that they use larger sample sizes and test a greater number of markers across DRD2/ANKK1 gene, and considering the publication bias that leaves many null results unreported, there is little evidence of association between DRD2/ANKK1 and alcohol phenotypes. It does appear however, that most of the studies that used quantitative/continuous measures of alcohol use and problems provide positive evidence of genetic association between DRD2/ANKK1 and alcohol related traits. This may reflect the fact that using quantitative measures can increase power to detect genetic association (Waldman et al., 1999, Kuo et al., 2010). However, it is of note that the largest of the aforementioned studies (Schumann et al., 2011), a meta-analyses of alcohol consumption GWAS on over 21,000 individuals, did not
