The present meta-analysis identified much stronger evidence for association than previous meta-analyses, as shown below. One study(Whitfield 1997) only included five studies of alcoholism, and the latest dataset was published in 1995. Another study(Zintzaras et al. 2006), in which the latest dataset was published in 2004, (i) included 24 studies, compared to 53 studies in the present meta-analysis; (ii) only included English-language literature; and (iii) did not consider association with alcoholic liver diseases. Compared with the previous meta-analyses, our study included the largest sample size up to 2010 from 49 English and four Chinese publications (it was important to include Chinese-language publications as well); investigated both AD and alcohol abuse as well as drug dependence; applied both strict and extended criteria; performed both allelic and genotypic analyses under the strict random effects model; and applied a comprehensive and systematic analysis precedure, as shown in the results, to study additional questions not answered in those previous meta-analyses. Our meta-analysis found highly significant evidence of associations with AD and alcohol abuse as well as alcohol-related diseases, in particular, in Asians. In addition,
