Included in these analyses are subjects 11 to 15 years of age, their parents and siblings from the longitudinal SMOFAM study of environmental and genetic determinants of tobacco use (15–16). Characterization of phenotypes for tobacco use, including the acquisition and maintenance of smoking, as well as potential psychosocial and environmental predictors of substance use, were collected for this cohort. After identification and recruitment of probands and family members, a detailed intake assessment was performed that included sociodemographics and a complete cigarette smoking history. Genomic DNA was extracted from venous whole blood using a standard salt-based precipitation method (21).
