Report
13 September 2023
Summary
Complex interventions cover a number of different approaches, such as long causal chain interventions, where there are a number of steps between activities and outcomes, and multi-component interventions, where several elements are combined. They also include multi-target interventions (which support different groups in different ways), system-level changes and interventions which evolve over time.
To evaluate these complex interventions, trials must be designed that take into account and manage the complexity.
The report, published jointly by TASO and King’s College London, explores the following types of complex interventions: long causal chain interventions, multi-component interventions, multi-target interventions, system-level interventions and evolving interventions. It then provides guidance on the different approaches that can be taken to evaluate these complex interventions: pragmatic trials, longitudinal trials, complex trials, adaptive trials, factorial trials, split plot trials and stepped wedge trials.
The report also highlights case studies where a complex intervention has been evaluated, such as TASO’s randomised controlled trial to understand the impact of summer schools and evaluation of multi-intervention outreach and mentoring.
The report is a version of a chapter written for the Ochre Book, which is funded under the DUPLO project funded by the UK Cabinet Office.