Development and evaluation of a theory- and evidence-based smartphone app to help reduce excessive alcohol consumption

This PhD research programme aimed to develop and evaluate a smartphone app to reduce excessive alcohol consumption and used the theoretical framework of the Behaviour Change Wheel to guide its development and evaluation. There are many different factors influencing alcohol consumption that can be targeted in an intervention to reduce excessive alcohol consumption. This thesis focuses on the cognitive and motivational factors affecting alcohol consumption. The thesis involves three stages: i) work informing intervention content to prioritise for inclusion; ii) the development of the app; and iii) evaluation of the app. The first stage involved four studies about who uses apps to reduce excessive alcohol use; how theory is currently used in existing digital alcohol interventions; people’s knowledge about how their drinking compares with others, and experts’ opinions on modules likely to be most effective in apps for reducing excessive alcohol consumption. Initial development and the first version of the app was based on pragmatic considerations as to how to deliver the intervention content, app developers’ opinion based on previous experience, previous delivery of similar intervention content, and frameworks for engagement and design. A person-based approach was taken in two usability studies conducted to inform further iterations and the final version. The app was evaluated using a factorial RCT to assess which intervention modules were most effective. The results of the trial relating to the cognitive and motivational factors suggest that the normative feedback and cognitive bias re-training modules may assist with drinking reduction and are worthy of including in an optimised app for further development and evaluation in a full-scale RCT.