Participants were administered the TCI (Cloninger and Svrakic 1997; Constantino et al. 2002) to assess the personality dimensions of NS and SD. In addition, a proxy measure of SES was derived from parental occupation data. Parental occupations were classified into nine categories according to Hollingshead (1975) and the score categories were averaged for both parents. If only one parent provided occupational data, the family was assigned a score based on the available data from one parent. Occupational score has been shown to correlate highly with education, income, and “prestige” rating (Hollingshead 1975) and thus can serve as a good proxy indicator of SES of the family. Participants were administered Missouri Assessment of Genetics Interview for Children (Todd et al. 2003), a semi-structured, diagnostic interview for children and adolescents that has been developed and extensively used in epidemiological family genetic studies of psychiatric disorders in adolescents. In addition, participants completed a paper-and-pencil substance use screen.
