One additional possibility is that the transition into middle school and its accompanying reduction in adult monitoring and increase in youth affiliation with deviant peers opened new opportunities and support for substance use and sexual activity that were not reduced effectively with the youth-focused case management that Fast Track provided during the middle school years. Interestingly, although child kindergarten characteristics significantly predicted the timing of sexual debut and pregnancy, they were not associated with the timing of tobacco or alcohol/drug use initiation. These concurrent risks appear more heavily associated with peer-group norms and opportunities, and hence require attention to the peer context to reduce risk. Certainly, additional research examining the Fast Track intervention, as well as future research examining alternative intervention approaches is critically needed to better understand causal pathways and mechanisms associated with effective prevention targeting the tri-morbidity of antisocial behavior, substance use, and risky sexual activity among youth with early-starting conduct problems. Given the present findings, an expanded and differentiated prevention model may be needed to address alternative risk/protective mechanisms and diverging developmental trajectories characterizing youth at different
