In-home–based visits were conducted twice in sixth grade (in the 2003 fall and spring, Waves 1 and 2) and annually in the spring thereafter for 3 years (Waves 3, 4, and 5). The in-home procedures included written questionnaires completed independently by the adolescent; mother; and, if present, father. During Wave 5 of the in-home assessment, in which 749 families took part, parents were asked to consent for adolescent DNA data collection. In addition to the 537 DNA samples collected at that point, a later data collection by mail in young adulthood provided an additional 57 samples, for a total of 594 in-home participants who provided saliva samples for DNA data. Of those who provided DNA, 98.5% were successfully genotyped for the DRD4 polymorphism. For purposes of the current article, children were included in these analyses only if they lived in a household where the coresident parents were married or in a marriage-like relationship at the initial assessment (see also Fosco & Feinberg, 2014). The final analysis sample consisted of 452 families. Comparisons between our analytic sample and the larger population
