Measures of alcohol initiation and lifetime alcohol use disorders were coded from the Semi-Structured Assessment for the Genetics of Alcoholism Interview (Bucholz et al., 1994; Hesselbrock et al., 1999). Age of initiating regular drinking was coded from participants’ response to the question, “At what age did you begin to drink regularly; that is, drinking at least once a month for 6 months or more,” measured in years. Lifetime diagnoses (binary) of alcohol use disorder were made based on Diagnostic and Statistical Manual of Mental Disorder (DSM-5) criteria (American Psychiatric Association, 2013). To ensure that participants had passed through the period of highest risk for onset of AUD before being classified as unaffected, those <23 years of age at their assessment who were without an AUD diagnosis were set to missing.
