Institutionalisation of health impact assessment. A systematic scoping review and development of a descriptive conceptual framework

Health impact assessment (HIA) is a flexible, evidence-informed process used to evaluate the health and equity implications of decisions, policies and plans. While HIA has gained global traction, its institutionalisation - defined as the systematic integration of HIA into decision-making - remains uneven across contexts. This paper explores how HIA institutionalisation is conceptualised, identifying key facilitators, barriers and conditions that shape its implementation. A systematic scoping review including 24 peer-reviewed studies and grey literature, and an online workshop with 17 experts was undertaken. Results indicated key facilitators for institutionalisation of HIA included legislation, guidance and dedicated resources; barriers were the absence of these. Findings informed a conceptual framework for HIA institutionalisation with four stages, advocacy, adoption, implementation and institutionalisation, supported by a 'wall of institutionalisation' of enabling activities. This was applied to Wales to appraise maturity. It demonstrated that legislation including the Public Health (Wales) Act 2017 has created an enabling environment for HIA, underpinned by numerous activities and a dedicated HIA Support Unit. The discussion offers transferable learning and actionable insights for policy, research and practice, highlights future areas of development and provides a practical roadmap and maturity baseline for systems seeking to institutionalise HIA.