Results for onset of regular smoking are shown in Table 7. For all models, and across risk group, parent and cotwin alcohol and cannabis dependence could be equated. In Model III, Group 2 offspring of unaffected parents with a substance dependent identical cotwin were at 2.72 times higher risk of regular smoking, compared to controls (Group 4). Parental separation was uniquely associated with 3.37 times higher likelihood of regular smoking through age 13 only.
