The Missouri Adolescent Female Twin Study (MOAFTS) is a cohort of same-sex female twin pairs, identified from birth records, born between July 1st 1975 and June 30th 1985 to Missouri-born parents (see (21-23)). As a subset of the participants were 12-15 years of age at baseline, sensitive questions regarding cannabis use were not administered to them at that initial wave of data collection. During 2002-2005, all eligible twins who were then adults, regardless of whether they had participated in the baseline assessments or not (and as long as they had not declined to participate in future interviews), were invited to participate in the first full-length adult follow-up interview. This sample, which represented 80% of all live female twin births in the state, consists of 3,787 twins (including 964 monozygotic or MZ and 809 dizygotic or DZ pairs, as well as 241 un-paired twins who did not have a participating co-twin) aged 18-27 years, including 14.6% of African-American ancestry. Data on 2,950 (15.9% African-American) twin women who reported a lifetime history of any consensual sexual activity were included in the current
