Background: Complex interventions pose significant challenges for Cochrane Reviews, especially when there is lack of consensus in a particular field with relatively little experience or commitment to RCTs. In a review of a widely used complex intervention we found five RCTs but little agreement on how the interventions were described or the outcomes selected.

Objectives: To demonstrate a systematic approach to managing a complex intervention in a Cochrane Review.

Methods: We compared interventions and outcomes from five RCTs by mapping components to a conceptual model (derived from theory) developed for the protocol and by applying common Cochrane approaches to minimise bias. Outcomes were grouped into categories to increase the potential for meta-analyses.

Results: The evidence generated by the review was low to medium quality due to methodological weaknesses in the included studies. However all components in the conceptual frameworkwere addressed and outcomes for all primary outcomeswere identified. The conceptual framework provides the basis for further work to establish agreement on the core components of the intervention and how the intervention can be evaluated in future trials.

Conclusions: The processes of the review provided the means to develop a robust framework that will be used to develop consensus on how a complex intervention will be described and evaluated in future studies.