Participants took part in a life history calendar interview (Cohen et al., 2003; Freedman et al., 1988). They were asked to report their average monthly alcohol consumption (frequency and quantity) at different ages. These data were then combined into ages that correspond to meaningful developmental age ranges, as reported previously in Edwards and Kendler (2013): the ages used for the current report were 12–14, 15–17, 18–21, and 22–25. Mean alcohol consumption was calculated for these age ranges, with abstainers assigned values of 0. To each average consumption score, 1 was added, followed by a natural log-transformation to adjust for non-normality. Thus, the lowest possible log-transformed score was 0, corresponding to abstainers. These variables will be referred to as SELF1-SELF4.
