from sources such as dental clinics and motor vehicle records. Subjects in comparison families were not prescreened and may be expected to have population rates of common disorders such as AUD (2). Subjects in the dataset were included in analyses regardless of initiation of alcohol use by the time of the baseline interview. More than 80% of subjects participated in at least one follow-up. The average number of interviews per subject was 4.0 (SD = 1.7). There was no evidence for selective attrition of affected subjects (22). All subjects had data on comorbid diagnoses, AUD diagnosis, peer drinking, and age of first drink. Genotyping was carried out and quality control procedures applied as previously described (41,42). Ancestry was assigned based on the first four genotypic principal components of population stratification (Figure S1). Individuals surrounding the CEU HapMap position were assigned to the EA sample, and those beyond a radius of about 0.002 units on the principal component 1 axis were assigned to the AA sample. To maintain power for family-based analyses, final ancestry assignment was based on the majority of individual family members. Families with an equal distribution were assigned to the most diverse group (AA). This analysis excluded subjects
