A potential limitation of our findings is that measurement issues may have influenced our examinations of between-group differences in family history density of alcohol problems, as well as of associations between P300 measures and family history density of alcohol problems. Specifically, we measured family history density of alcohol problems by counting the number of first-degree relatives with whom the participant had cohabited and who had an alcohol-use problem; other studies (e.g., Fein and Chang, 2008; Mann et al., 1985) did not restrict their measurement of this variable to cohabiting relatives, but instead calculated the proportion of first-degree relatives with an alcohol-use problem. Nevertheless, we maintain that our findings are sound, as they are consistent with predictions based on the expectation of lower genetic vulnerability to alcoholism in TNAD versus treated samples (Di Sclafani et al., 2008).
