Using intervention trials in developmental psychiatry to illuminate basic science.

We discuss the nature of intervention in developmental psychiatry and the implication of this for clinical trials. New ideas in the design of randomised trials for complex interventions, along with recent statistical advances in causal analysis, give such trials additional potential as a means by which to study the basic science of complex developmental disorders. The challenge for designers of trials is to model designs effectively to make best use of these new opportunities. We give examples of how this might be done and discuss implications for future trials designs in the area.