there also exists symptom-specific genetic variance that may be imparted by the study of multiple factors (as previously suggested using a multivariate twin study approach (Kendler et al., 2012)). This latter point was recently reflected in a report by Hart and colleagues which showed variation in the association between common genetic variants within the alcohol dehydrogenase gene (ADH1B) and each of the diagnostic symptoms of AD (Hart et al., 2016). In perspective, Hart and colleagues were able to determine that previously observed AD genomewide association study (GWAS) associations (Gelernter et al., 2014), for example, in their subjects of African ancestry (i.e., rs2066702 with AD), were primarily driven by signals specific to phenotypic variation in the symptoms ‘Tolerance’ and ‘Much time spent using/recovering from the effects of alcohol’. This observation is important as phenotype-genotypic associations from GWAS are used to inform gene function studies in tissue/cell culture and/or model organisms.
