Objectives Our aim was to synthesize published scholarship that applies policy diffusion—a theory of the policy process that considers the interdependence of government-level public health policy choices. We paid particular attention to the role of scientific evidence in the diffusion process, and to identifying challenges and gaps towards strengthening the intersection of public health, public policy, and political science. Methods We systematically searched 17 electronic academic databases. We included English-language, peer-reviewed articles published between 2000 and 2021. For each article, we extracted the following information: public health policy domain, geographic setting, diffusion directions and mechanisms, the role of scientific evidence in the diffusion process, and author research discipline. Synthesis We identified 39 peer-reviewed, primary research articles. Anti-smoking and tobacco control policies in the United States (n = 9/39) were the most common policy domain and geographic context examined; comparatively fewer studies examined policy diffusion in the Canadian context (n = 4/39). In terms of how policies diffuse, we found evidence of five diffusion mechanisms (learning, emulation, competition, coercion, and social contagion), which could moreover be conditional on internal government characteristics. The role of scientific evidence in the diffusion process was unclear, as only five articles discussed this. Policy diffusion theory was primarily used by public policy and political science scholars (n = 19/39), with comparatively fewer interdisciplinary authorship teams (n = 6/39). Conclusion Policy diffusion theory provides important insights into the intergovernmental factors that influence public health policy decisions, thus helping to expand our conceptualization of evidence-informed public health. Despite this, policy diffusion research in the Canadian public health context is limited.

Governments face challenges in resolving complex health and social policy conflicts, such as the community water fluoridation (CWF) impasse in Calgary. Track Two diplomacy, informal dialogues facilitated by an impartial third party, is proposed to address these issues amid epistemic conflict and declining public trust in fellow citizens, science, and government. This study examined Track Two diplomacy’s application in Calgary’s CWF policy conflict. Collaborating with policymakers and community partners, the research team explored a Track Two–CWF process and conducted 21 semi-structured interviews with policymakers, scholars, practitioners, observers, and civil society representatives. Data interpretation explored contextual factors, conflict transformation potential, and design features for a Track Two process. A conflict map revealed factors contributing to impasse: the polarizing nature of a binary policy question on fluoridation; disciplinary silos; failed public engagement; societal populism; societal lack of disposition to dialogue; individual factors (adverse impact of conflict on stakeholders, adherence to extreme positions, issue fatigue, apathy, and lack of humility); together with policy-making factors (perceived lack of leadership, lack of forum to dialogue, polarization and silos). Participants suggested reframing the issue as nonbinary, involving a skilled facilitator, convening academics, and considering multiple dialogue tracks for a Track Two process. The first theory of change would focus on personal attitudes, relationships, and culture. Participants expressed cautious optimism about Track Two diplomacy’s potential. Track Two diplomacy offers a promising approach to reframe intractable public health policy conflicts by moving stakeholders from adversarial positions to jointly assessing and solving problems. Further empirical evidence is needed to test the suggested process.