Pooling across cohorts in the full sample, the actual ages of assessment were 11.8 (SD=0.4), 14.9 (0.6), 17.8 (0.7), 21.1 (0.8), 25.0 (0.9), and 29.5 (0.7) years. Participation rates ranged from 87.3% to 93.6% for the follow-up assessments. To examine attrition, we compared 17-year-olds who did versus did not complete the adult assessments at age 20, 24, and 29. For males, Cohen’s d for mean differences in age 17 dependence symptoms between those who did (N=1570) versus did not (N=238) complete the later assessments were .00, −.08, and .09 for nicotine, alcohol, and marijuana, respectively. For females, Cohen d’s for similar comparisons were −.19, −.01, and .13 (all p’s>.05).
