<p>A conceptual modelling framework for developing the structure of Public Health economic models</p><p>Background: Public Health interventions tend to operate within dynamically complex systems and require consideration of a broader range of determinants of health than clinical interventions, including aspects of human behaviour and estimating impacts upon non- health costs and outcomes. The structural development of Public Health economic models is currently based upon ad hoc non-transparent methods. A conceptual modelling framework is a set of steps which can help to guide modellers through the development of a model structure. Key advantages of a conceptual modelling framework are to: aid the development of modelling objectives; provide tools for communication with stakeholders; guide model development and experimentation; improve model validation and verification; and allow model reuse. This paper describes a conceptual modelling framework for Public Health economic models. </p><p>Methods: The framework was informed by two literature reviews, qualitative research with modellers and a pilot study. The literature reviews aimed to: (1) describe the key challenges in Public Health economic modelling and (2) review existing conceptual modelling frameworks within the broader literature. The qualitative research aimed to understand the experiences of modellers when developing Public Health economic model structures and their views about the barriers and benefits of using a conceptual modelling framework. This involved; (i) following the development of a Public Health economic model including observing key meetings and undertaking in-depth interviews with the modellers involved; (ii) systematically analysing my own notes from a previous Public Health economic project; and (iii) holding a focus group meeting with modellers. A draft version of the conceptual modelling framework was piloted within a project assessing the cost-effectiveness of interventions for diabetes screening and prevention.</p><p>Results: Four key principles of good practice were identified; (1) that a systems approach to Public Health modelling is appropriate (feedback loops & unintended consequences are important); (2) developing a thorough documented understanding of the problem is valuable prior to and alongside developing and justifying the model structure; (3) that a systematic consideration of the determinants of health is central to identifying all key impacts of the interventions within Public Health economic modelling; and (4) that strong communication with stakeholders and members of the team throughout model development is essential. The conceptual modelling framework is described within the paper. </p><p>Discussion: A framework has been developed as a helpful tool for modellers of Public Health economic models. Initial evaluation will be via a focus group with modellers. It is offered for further testing within case studies. </p>