In terms of different phenotypes, when the samples of subjects diagnosed with heroin and other drug dependence (only three studies, and they were investigating the European and African populations) were combined with those of AD and alcohol abuse as an independent meta-analysis, based on the hypothesis that different types of addictions may share some common genetic risks(Fu et al. 2002; True et al. 1999; Xian et al. 2008), no significant change was found in the associations. Strong evidence of association was still identified using allelic and genotypic analyses in all the combined populations, combined Asians and Europeans, and combined Mexicans and Africans, but not in Europeans. The results of overall and sub-grouped analyses are shown for both allelic and genotypic analyses in Table 1. The forest plots of the allelic analysis and dominant model are shown in Figures 1 and 2; and the plots of the recessive model are shown in supplementary Figure 1.
