All SIBS participants, both parents and children, underwent structured interviews including the assessment of DSM-IV diagnostic criteria, producing symptom counts and diagnostic status for alcohol abuse and alcohol dependence. Diagnostic data for parents (who were assessed at intake only), covered parental lifetime. Diagnostic data for sibling participants covered lifetime for assessment at intake, and covered the interval elapsing since their last assessment (typically over 3 years) at FU1 and FU2. To account for the possibility that symptoms may be forgotten when reporting on past disorder, participants were classified as alcohol dependent if they satisfied criteria for either definite (meeting all DSM-IV criteria) or probable (missing one symptom) alcohol dependence. Alcohol abuse, which requires only one symptom, was diagnosed only when full DSM-IV criteria were met.
