Regression models predicting CBCL internalizing, externalizing, and total problems scores from parent and co-twin AUD were conducted in STATA (StataCorp, 2005), with post-hoc tests for group differences. All models included three dummy variables coding for offspring at both high genetic and high environmental risk (Group 1: parent AUD+), offspring at high genetic risk but reduced environmental risk (Group 2: parent AUD-, MZ co-twin AUD+), and offspring at intermediate genetic risk but reduced environmental risk (Group 3: parent AUD−, DZ co-twin AUD+). Control families, where offspring are at low genetic and low environmental risk (Group 4: parent and co-twin AUD−), comprised the reference group. Analyses were conducted first without and then with adjustment for offspring age and gender. The Huber-White robust variance estimator option in Stata was used to correct for non-independence of twin-family data.
