Six Steps in Quality Intervention Development (6SQUID)

Background Improving the effectiveness of public health interventions relies as much on the attention paid to their design and feasibility as to their evaluation. Yet, compared to the vast literature on how to evaluate interventions, there is little to guide researchers or practitioners on how best to develop such interventions in practical, logical, evidence based ways to maximise likely effectiveness. Existing models for the development of public health interventions tend to have a strong social-psychological, individual behaviour change orientation and some are impractical and require years to implement. Methods Drawing on the strengths of existing frameworks, and on our own experiences, we will present a pragmatic guide to six essential steps of intervention development. The focus is on social interventions to improve public health, however we hope that the model might be useful for intervention development beyond public health. Results Once a problem has been identified as needing intervention, the six crucial steps that should be taken are: 1. defining and understanding the problem and its causes; 2. identifying which causal or contextual factors are modifiable: which have the greatest scope for change and who would benefit most; 3. deciding on the mechanisms of change (theory of change); 4. clarifying how these will be delivered (theory of action); 5. testing and adapting the intervention; and 6. collecting sufficient evidence of effectiveness to proceed to a rigorous evaluation. Conclusions We argue that the process of designing social interventions can be broken down into these six key steps. We hope that if each of these steps is carefully addressed better use will be made of scarce public resources by avoiding the costly evaluation, or implementation, of unpromising interventions. Key messages Compared to the vast literature on how to evaluate interventions, there is little to guide researchers or practitioners on how best to develop social interventions for public health. 6 steps for intervention development: 1 understand problem; 2 identify modifiable causal factors; 3 decide mechanisms of change; 4 clarify delivery; 5 test and adapt; 6 get evidence of effectiveness.