In a recent meta-analysis of twin (and adoption) studies, the heritability of alcohol use disorders was estimated to be between 47% and 54%,18 with the remaining variance attributable to environmental factors. However, this compilation of the extant literature underscores how the body of studies used to examine the heritability of alcohol problems overwhelmingly consists of homogeneous samples of European ancestry. Twin and adoption studies examining alcohol-related phenotypes have generally used samples from national populations with relatively little diversity (such as those in Sweden and Finland) or have focused exclusively on non- Hispanic, European American (EA) twins even in countries with greater racial diversity (such as in the United States).18 Of the samples included in the meta-analysis, only the Vietnam Era Twin Registry included twins not of European descent. Potential differences in the importance of genetic and environmental influences across individuals of differing racial backgrounds was not even discussed in this meta-analytic compilation of the literature. The meta-analysis is representative of the broader historical problem of a lack of racial diversity in twin registries, especially in the United States and Europe.
