The sample of 7188 individuals clustered in 2300 families was drawn from participants in ongoing longitudinal research at the Minnesota Center for Twin and Family Research (MCTFR). Families consisted of a pair of offspring and their rearing parents, although some members of participating families are not included in the present study because either they did not contribute a DNA sample, did not complete the phenotypic assessment, or did not meet this study’s definition of being of European ancestry (see below). Family type is distinguished by offspring relationship, which is either monozygotic twins, dizygotic twins, full biological siblings, adopted siblings, or mixed siblings with one being biologically related to the parents and the other being an adopted child. The sample included 3852 parents, 2072 women (mean [SD] age = 42.8 [5.3]) and 1780 men (44.9 [5.7]), and 3336 offspring, 1788 women (18.0 [0.8]) and 1548 men (17.9 [0.7]). Because offspring had completed multiple longitudinal assessments, we selected measures for the analysis reported here from the assessment that took place closest to their 17th birthday, so long as that assessment was completed
