The importance of a person-oriented approach was highlighted by the different profiles of problem co-occurrence that emerged in this study. Four distinct profiles emerged for girls and boys, based on the timing of initiation of three risk behaviors (sexual intercourse, tobacco use, alcohol/drug use) and indicators of risky sex (adolescent pregnancy, STD). Three of the classes were distinguished by risky behaviors (and included more early-starting aggressive youth than normative peers), but only two of these classes showed elevated sexual risk. Specifically, the “preadolescent multi-problem” class, characterized by the very early initiation (by 8th grade, age 13–14) of all three risky behaviors (sexual intercourse, tobacco use, and alcohol/drug use) was at high risk for teen pregnancy (0.39 for boys, 0.55 for girls) and STDs (0.20 for boys, 0.44 for girls). The “adolescent multi-problem” profile (for boys) characterized by the mid-adolescent initiation of sexual activity, tobacco use and alcohol use, and “adolescent dual problem” profile (for girls, characterized by the mid-adolescent initiation of sexual activity and tobacco use also conferred risk for teen pregnancy (0.35 for boys; 0.72 for girls) and STDs
