We also measured the alcohol use of parents and sibling participants (including both target siblings and their co-siblings) aged 16 or older at the time of assessment using a modified version of the Substance Abuse Module (SAM; Robins, et al., 1987), which was originally developed to supplement the World Health Organization’s Composite International Diagnostic Interview (Robins et al., 1988). These measures were collected at all three assessment time points for sibling participants, but at intake assessment only for parents. To all sibling participants younger than 16 at the time of assessment, we administered a computerized substance use questionnaire, which included alcohol-use items re-scaled to be equivalent to those in the SAM. To index alcohol use for genotyped participants, older siblings, and parents, we used four items included on both the SAM and the computerized substance use questionnaire: frequency of drinking sessions over the year preceding the current assessment, average amount of alcohol consumed during drinking sessions over the year preceding the current assessment, maximum amount of alcohol consumed during a single drinking session over the participant’s lifetime until the current
