The CDP collected data on externalizing behavior using Achenbach's Youth/Young Adult Self-Reports at ages 12, 14, 15, 16, 17, 19, 20, 21, and 22 years.31,32 This widely used assessment battery33 consists of 113 items in the Youth version and 123 items in the Young Adult version, for which the participant indicates whether the behavior is not true, somewhat or sometimes true, or very or often true (scored 0, 1, and 2, respectively). The Externalizing Scale consists of 30 items in the Youth version and 28 items in the Young Adult version comprising both delinquency (eg, “I don't feel guilty after doing something I shouldn't”; “I cut classes or skip school”) and aggression measures (eg, “I am mean to others”; “I get in many fights”). These measures have been shown to have excellent psychometric properties including high test-retest reliability, content validity, criterion-related validity, and construct validity.34,35 Values of α in the present study ranged from .84 to .88.
