Vicissitudes of follow-up studies: differential effects of parent training and stimulant medication with hyperactives.

A two-year outcome study of 73 hyperactive children supports both previous short-term studies which suggested that stimulant medication is superior to parent training and long-term studies which found no differences between the two interventions. The discrepancy is discussed in light of complications that inevitably arise in outcome studies and that tend to preclude meaningful outcomes in long-term studies. The development of new research strategies is called for.