Surprisingly, risks to offspring associated with parental separation have received limited attention in research on children of alcoholic or other drug addicted parents. Using a Children-of-Twins (COT) design (Gotteman and Bertelson, 1989; Heath et al., 1985; Nance and Corey, 1976), we examine whether parental separation predicts early substance involvement over and above risks from parental alcohol or cannabis dependence, including genetic risks. Genetic variation has been reported for alcohol abuse and dependence (Heath et al., 1997; McGue, 1994) and a variety of drug use disorders, including cannabis abuse and dependence (Kendler and Prescott, 1998; Lynskey et al., 2002), with genetic variation also observed for initiation, regular use, and problem substance use during adolescence (Maes et al., 1999; McGue et al., 2000; Rhee et al., 2003). Heritable influences on marital status are reported as well, including genetic variation in likelihood of marriage (Trumbetta et al., 2007) and risk of divorce (McGue and Lykken, 1992), with at least one report of genetic covariation between alcohol dependence and both marital timing and survival (Waldron et al., 2011).
