This study has several limitations that should be considered, most notably the lack of harmonization across phenotypic, genotypic, and analytic methods. Because the data was taken from multiple ongoing studies designed and implemented independently, it is not feasible for measures and analytic protocols to be identical. Importantly, all sample genotypes were imputed to a common reference panel and screened to select a set of common markers meeting common quality control thresholds, and the phenotypes in all studies included a common set of DSM-IV alcohol dependence symptoms. We note specifically that the ALSPAC phenotype differed from the others in order to take advantage of existing GWAS results; however, the past-year factor score measure is also a more appropriate for this younger sample given that AUD symptoms are quite rare in this age range, when most initiation has only recently occurred and frequent consumption is still a deviant behavior (Substance Abuse and Mental Health Services Administration, 2014). Age difference between samples is also an important limitation, although we note that previous studies have found that the same genetic factors influence AUDs in
