By using archival records, the Stockholm study was able to obtain data on the entire sample of adoptees. Thus, prevalence rates for alcoholism are available for the total sample of biological parents and adoptees. Significant associations are found between Temperance Board registrations for biological fathers and their adopted-away sons (i.e., a risk ratio of 1.3) and for biological mothers and their adopted-away daughters (i.e., a risk ratio of 2.9). These ratios are consistent with a genetic contribution to alcoholism risk. However, the risk ratios for opposite-sex pair comparisons (i.e., mother-son and father-daughter pairs), although greater than one, are not statistically significant.
