Minimal attrition occurred across the 22 months of the study; 95.2% of the sample completed the follow-up data collection. The attrition rates were similar for the SAAF–T and control groups. DRD4 data were unavailable for 41 of the 502 participants; 2 youths declined to provide DNA samples, and the genotyping laboratory was unable to make a valid genotype determination for the other 39 youths. Comparisons on all study variables between adolescents with (n = 461) and without (n = 41) DRD4 data revealed one difference. Families in which adolescents were genotyped reported more financial downturns at pretest than did those in which adolescents were not genotyped (M = 3.63 vs. 2.27, t = 2.99, p < .003). This variable was controlled in all of the following data analyses.
