A systematic scoping review of how behavioural theories, models, and frameworks have been applied to the design, conduct, analysis or reporting of clinical trials.

Background Clinical trials provide much of the evidence that guides decision making about treatment and care but are often complicated to deliver. Trials can be thought of as complex systems with interacting individuals, as such behavioural science is a useful lens to investigate how trial processes may be improved. To guide selection of an appropriate behavioural theory, model, or framework to further enhance trial processes, we sought to map their past application within the design, conduct, analysis and reporting of clinical trials. Methods A systematic review to investigate scope of trials methods research that had utilised a behavioural theory, model, or framework was conducted through a database search and citation analysis. Publications investigating any part of the trial lifecycle (from design to reporting) through a behavioural lens were included. Results A total of 96 studies were included. A majority of these (n = 93, 97%) investigated trial conduct processes, such as recruitment and retention. Three behavioural theories, models or frameworks, the Theory of Planned Behaviour (n = 23, 24%), Social Cognitive Theory (n = 12, 13%), and the Theoretical Domains Framework (n = 30, 31%), accounted for more than two-thirds of those utilised. When compared to key stages of the Knowledge to Action cycle, approaches reported in included studies were most often utilised to “Identify a problem” within trials (n = 40, 42%). Conclusion A wide variety of behavioural approaches to study trial conduct were identified. However, the trial processes studied clustered within trial recruitment and largely used a few select approaches. Future research should assess whether these approaches are fit for purpose, as well as prioritising other trial areas for methods research.