It is useful if interventions, and their evaluations, draw explicitly on existing social science theories, so that findings can add to the development of theory. However, evaluators should avoid selecting ‘off-the-shelf’ theories without considering how they apply to the context in which the intervention is delivered. Additionally, there is a risk of focusing narrowly on inappropriate theories from a single discipline; for example, some critics have highlighted a tendency for over-reliance upon individual-level theorising when the aim is to achieve community, organisational or population-level change (Hawe et al., 2009).