Prenatal alcohol exposure is a risk factor for alcoholism (Baer et al., 2003), and it is a limitation that data on maternal alcohol consumption during pregnancy were not available. However, alcohol consumption among women was quite rare in Denmark when the cohort was established and thus not registered systematically (Zachau-Cristiansen and Ross, 1975) Despite the ability to control for parental social status, it is a potential limitation that the study had relatively limited covariate control pertaining to other factors that confer an increased risk of alcoholism, for instance parental loss (Kendler et al., 2002) or deprived circumstances during childhood (Osler et al., 2006).
