The associations between each child outcome (INATT, HYP/IMP, CDP, and AlcProb) and prenatal (e.g., prenatal substance exposure) and parental (e.g., alcohol dependence, smoking behavior outside of pregnancy) predictors were investigated using linear regression models. Both members of each twin pair were included in these regression analyses; therefore, confidence intervals were adjusted to allow for the non-independence of twin pairs using the Huber-White robust variance estimation option as implemented in STATA (StataCorp, 2003).
