Subjects were from the National Youth Survey Family Study (NYSFS), a nationally representative household sample of 1725 original respondents across 1044 households who were between the ages of 11 and 17 in 1976 and living in the United States in 1977 (Elliott et al., 1989). In 2002 a follow up interview was conducted at which buccal cell DNA was collected on a voluntary basis. At the time participants were between 35 and 44 years of age. In addition to DNA collection, as part of a face-to- face structured interview, alcohol and tobacco use behaviors were assessed using an adaptation of the Composite International Diagnostic Interview - Substance Abuse Module (CIDI-SAM) (Cottler & Keating, 1990). Overall phenotype information and DNA was available for 1071 subjects, 48.1% male and 51.9% female, of whom 227 belonged to families with sibships ranging from 2 to 5 offspring (592 individuals) and 479 were individuals without siblings in the study (siblings may have been too old or too young to be recruited in 1977). The majority of the subjects are Caucasian (80.3%), with 12.3% African American, and 5.4% of Hispanic or other ancestry.
