Despite well-documented associations between problem substance use and relationship instability, risks to COAs associated with parental separation or divorce have received limited empirical attention, and this is especially true of children of parents with other drug dependence. In the present study, we examined initiation of substance involvement as a function of parental separation using a Children-of-Twins (COT) design to control for both genetic and environmental risks associated with parental substance dependence. Although parental alcohol and cannabis dependence were initially modeled separately, with few exceptions, effects could be equated. Thus, for most models we subsequently examined risks from parental substance dependence broadly defined, i.e., parental history of alcohol or cannabis dependence.
