The present findings highlight the contributions of both paternal substance dependence and parental separation to offspring alcohol involvement examined across adolescence and early adulthood. Among the many strengths of our study is a sample that is substantially larger with offspring several years older than in previous reports (e.g., Jacob et al., 2003; Sartor et al., 2007; Waldron et al., 2014a); consequently, we have increased statistical power to detect risk of alcohol problems and disorder relative to earlier work. The selection for DD as well as AD in the twin fathers also generalizes findings from studies focusing only on paternal AD, showing roughly equivalent prediction for paternal DD. Furthermore, fathers’ AD/DD histories were derived from their own reports, unlike other studies that have relied on family history. Finally, and importantly, we used time-varying covariates to ensure the temporal primacy of parental separation relative to alcohol transitions. As noted, the effect of parental separation on alcohol involvement varied considerably by age or “risk period”, underscoring the importance of modeling time-varying risk where age of onset data are available.
