These findings should be interpreted in the context of several limitations. Although we believe that the demonstration of similar effects across 2 independent samples is a strength of the study, we note that the exact measures of alcohol use and alcohol problems collected in the 2 projects differed. Even when the construct was the same (e.g., drinking frequency), the exact wording of the item and response options varied across the samples. Differential reliabilities and distributional properties of the items could have influenced the emergent genetic factor structures. Differences in psychometric properties across the samples likely contributed to some of the observed sample variability. We believe that the convergence of results across these studies is notable, given that the samples contained slightly different measures of current consumption and different indices of problem drinking, covered different age ranges (the FT16 sample was limited to young adults while the VATSPSUD sample covered a much broader age range of adults), and come from different drinking cultures.
