VTSABD is an ongoing cohort-longitudinal study of twins born 1974–1983; 1412 families were included in the first wave of data collection, with 3 subsequent waves of data collection occurring at approximately 1½-year intervals, and a 5th wave when participants were in their mid-20s (Simonoff et al., 1997). A sample of 1894 putative twin pairs was ascertained through the state school system and participating private schools in Virginia, and through families who contacted the VTSABD. A total of 1412 families (2775 children) participated (75%). Up to age 18, children and parents completed the Childhood and Adolescent Psychiatric Assessment. Parents completed a similar assessment on both twins. After age 18 the twins alone were interviewed using an age-updated interview designed for telephone administration. Whole blood was collected from VTSABD subjects and DNA extractions were completed at Rutgers University Cell and DNA Repository. A total of 603 unrelated VTSABD subjects, contributing 1441 repeated alcohol consumption assessments, were analyzed in genome-wide association testing.
