Abstract
In health promotion research, enthusiasm for patient and public involvement (PPI) is growing. However, a lack of conceptual clarity leads to ambiguities in participatory processes and purposes, and hampers efforts to achieve and evaluate PPI in research. This study provides an overview of its underlying reasons-or rationales-so as to better understand, guide and interpret PPI in research practice. We conducted a critical review to identify typologies of rationales for PPI. We re-categorized the different types of rationales from these typologies based on their content. We illustrated the resulting categories of rationales with examples from a case study on PPI in research on Lyme disease. Five categories of rationales for PPI were identified. The democratic rationale reflects the normative right of citizens to have a voice in research. The consumerist rationale refers to the economic right of stakeholders with interests to have a say. Rooted in social justice, the transformative rationale seeks to empower marginalized groups. The substantive rationale starts from epistemic considerations and aims to improve the quality of knowledge that research generates. The instrumental rationale is of pragmatic origin and refers to improved efficiency and effectiveness of the research. Our overview of categories of rationales can be used as a frame of reference for PPI in health promotion research. Exploring, stating explicitly and reflecting on the underlying reasons for PPI may help to define realistic purposes, select matching approaches and design appropriate evaluation studies. This might also contribute to the conceptualization of PPI.