The relationship between adoption status (adopted/non-adopted), exposure to parent smoking (ever/never), and adolescent adjustment was investigated using analysis of variance (AVOVA) for quantitative outcomes and logistic regression for categorical outcomes. The basic model included adoption status, exposure, and their interaction as independent variables. The significance of each variable was measured net the other variables in the model, a regression approach to the analysis of genetically informative data24. Adolescent age and ethnicity (Caucasian/non-Caucasian), and family SES were included as covariates. Dependent variables included a diverse array of adolescent substance use and other disinhibitory outcomes. The correlated nature of the family data was taken into account with hierarchical linear methods as incorporated into PROC MIXED (for quantitative outcomes) and generalized estimating equations (GEE) as incorporated into PROC GENMOD (for categorical outcomes) from the Statistical Analysis System (SAS)22. Analyses were structured to estimate the simple main effect of exposure to parent smoking in the adopted and non-adopted adolescents separately. For quantitative outcomes, effect sizes (ESs) were estimated by dividing the difference in the covariate-adjusted means by the residual standard deviation. For categorical outcomes, covariate-adjusted odds ratios (ORs) and confidence intervals are reported.
