Biological coparent history of substance use or disorder was also coded as offspring phenotypes depend on behavior of both parents even when mating is random (Eaves et al., 2005). Consistent with research documenting strong within-family agreement (Waldron et al., 2012), coparent alcoholism was coded positive by twin, coparent or offspring report. In MATCH, AD symptoms experienced by biological coparents were assessed without regard to temporal clustering; thus, a probable dependence diagnosis was coded. In PACER, twins were asked only whether “drinking ever caused the biological (mother/father) of (child1/2/3) to have problems with health, family, job or police, or other problems,” an item that originated in the Family History Research Diagnostic Criteria assessment (FHRDC; Andreasen et al., 1977), and whether they ever felt that the coparent was an “excessive drinker.” In both MATCH and PACER, offspring ages 15 and older were asked similar questions, that is, whether “drinking ever caused your biological (mother/father) to have problems…,” and whether they were an “excessive drinker.” Endorsement of both problem and excessive drinking was required to code a coparent positive by twin report (in
