Carrots, sticks and health behaviours: a framework for documenting the complexity of financial incentive interventions to change health behaviours.

Financial incentive interventions are increasingly used as a method of encouraging healthy behaviours, from attending for vaccinations to taking part in regular physical activity. There is a growing body of research on the effectiveness of financial incentive interventions for health behaviours. Wide variations in the nature of these interventions make it difficult to draw firm conclusions about what makes an effective incentive, for whom and under what circumstances. Whilst there has been some recognition of the theoretical complexity of financial incentive interventions for health behaviours, there is no framework that categorises these interventions. This limits the research community's ability to clearly establish which components of financial incentives interventions are more and less effective, and how these components might interact to enable behavioural change. We propose a framework for describing health-promoting financial incentive interventions. Drawing on our experience of a recently completed systematic review, we identify nine domains that are required to describe any financial incentive intervention designed to help individuals change their health behaviours. These are: direction, form, magnitude, certainty, target, frequency, immediacy, schedule and recipient. Our framework should help researchers and policy-makers identify the most effective incentive configurations for helping individuals adopt healthy behaviours.