The NEAD sample was comprised of 721 White (94%) families of twins and siblings who participated in the NEAD project (Neiderhiser, Reiss, & Hetherington, 2007). Families were predominantly recruited through a national market survey of 675,000 families, supplemented with random digit dialing of 10,000 telephone numbers throughout the United States. Zygosity was established using a validated questionnaire (> 90% agreement with genotyping) (> 90% agreement with genotyping; Goldsmith, 1991) on which adolescent twins were rated for physical similarity (Nichols & Bilbro, 1966). Three years after the initial assessment, adolescents who still resided primarily at home were invited to participate in a follow-up assessment. We used data from the 408 twin/sibling pairs who participated in the second assessment (to match the ages of adolescents in TOSS). There were 63 monozygotic twin pairs (MZ), 75 dizygotic twin pairs (DZ), and 58 full sibling pairs (FI) in non-divorced families, and 95 full sibling pairs (FS), 60 half sibling pairs (HS), and 44 genetically unrelated sibling pairs (US) in stepfamilies who were together for at least 5 years at the time of the first
