History of parental alcoholism was coded from parent self-report of alcohol dependence (AD), parent ratings of coparent dependence symptoms, and twin ratings of each parent as a problem and excessive drinker. Parent interviews included self-report assessment of lifetime history of AD, with AD symptoms experienced by the twins’ biological coparent assessed using an adaptation of the Family History Assessment Module (Rice et al., 1995). Temporal clustering of coparent symptoms was not assessed, thus a probable dependence diagnosis without requiring 12-month clustering was coded for coparent AD. Twin ratings of each parent were drawn from Wave 4, when all twins were aged 18 or older. Twin interviews did not ask detailed questions about parental dependence symptoms; instead, twins were asked whether “drinking ever caused your biological (mother/father) to have problems with health, family, job or police, or other problems,” an item that originated in the Family History Research Diagnostic Criteria assessment (Andreasen et al., 1977), and whether they ever felt that their biological parent was an “excessive drinker.” Endorsement of both problem and excessive drinking items was required to code a
