Results from the current analyses must be considered in light of several limitations, however. Our reliance on lifetime history of parental substance dependence may underestimate the impact of chronic substance dependence. For example, some parents may have remitted prior to starting a family, or had delayed DD/AD onset that post-dated childrearing. We also cannot know from these data why parents separated, or for how long relationship problems existed prior to separation. Although tests of interactions between paternal substance dependence and parental separation were not significant, if substance dependence was a primary reason for separation, it is possible that the departure of a substance dependent parent from the home might reduce risk to offspring. In addition, we did not examine genetic and environmental sources of risk from parental separation. In the handful of studies to do so, findings are generally suggestive of environmental transmission from parental separation to alcohol problems (D’Onofrio et al., 2005, 2007), but equivocal regarding timing on alcohol use (D’ Onofrio et al., 2006). Analyses that model genetic and environmental risks from both parental substance dependence and parental
