Building realist programme theory for large complex and messy interventions

Programme theory, that is, the specific idea about how a programme causes the intended or observed outcomes, should be the central aspect of any realist evaluation or synthesis. The methods used for explicating or building initial rough programme theories in realist research are varied and arguably often underreported. In addition, pre-existing psychological and sociological theories, at a higher level of abstraction, could be used to a greater extent to inform their development. This article illustrates a method for building initial rough programme theories for use in realist research evaluation and synthesis. This illustration involves showing how the initial rough programme theories were developed in a realist evaluation concerning sexual health services for young people. In this evaluation, a broad framework of abstract theories was constructed early in the process to support initial rough programme theory building and frame more specific programme theories as they were developed. These abstract theories were selected to support theorising at macro, meso and micro levels of social structure. The paper discusses the benefits of using this method to build initial theories for particular types of interventions which are large, complex and messy. It also addresses challenges relating to the selection of suitable theories.