Data from all offspring interviews were used to obtain lifetime reports of substance use and consensual sexual debut; age at onset for each behavior was based on first report. For subjects who had already initiated a particular substance or sexual debut at the baseline interview or had only one interview (52.9%), retrospectively-reported age at first use or first sex was used. Age was recorded in years since birth, in yearly increments. Substance use variables came from the alcohol, cannabis, and tobacco assessments of the SSAGA and C-SSAGA interviews, and sexual debut from a question in the antisocial behaviors section about age at first sexual intercourse. Subjects were first asked “Have you ever had sexual intercourse voluntarily?”, and if “yes”, “How old were you when you first had sexual intercourse (voluntarily)?”
