Prevention/Intervention trials and developmental theory: commentary on the Fast Track special section.

Well-conducted prevention and intervention research has the potential to serve the dual ends of enhancing children's adaptive outcomes and elucidating important developmental processes and mechanisms related to change. Admirably, the Fast Track preventive intervention was conceived in accord with explicit developmental theory related to the development of conduct problems. Herein, I consider how the present reports of grade-3 outcomes allow examination of causal processes and developmental mechanisms related to the effects uncovered, featuring the constructs of prediction, moderation, and particularly mediation. The multifaceted, intensive nature of the Fast Track preventive intervention is at once a clinical strength and a liability in terms of isolating causal processes underlying child change. I also consider issues related to the random assignment of the investigation and to policies that may emerge from the findings. In all, research that aims to identify relevant developmental and causal processes must incorporate both experimental and nonexperimental paradigms that are conceptualized from the outset with explanatory purposes in mind.