Results for first cannabis use are shown in Table 8. For all models, and across risk group, parent and cotwin alcohol and cannabis dependence could be equated. In the fully adjusted Model III, risk to Group 2 only was significant, with offspring of unaffected parents with a substance dependent identical cotwin at 3.03 times higher risk of early cannabis use, compared to controls (Group 4). Parental separation was uniquely associated with over three times higher likelihood of early cannabis use through age 13 (HR=3.25).
