INTRODUCTION:
Trust and mistrust influence how individuals interact with health organizations, shaping cooperation, adherence, and institutional legitimacy(1-3). While trust facilitates collective action(4), mistrust can constitute a rational response to inequity or institutional failure(5). Yet evidence surrounding these constructs remains fragmented. This systematic review synthesizes two decades of research to clarify definitions, determinants, measurement approaches, and interventions related to trust and mistrust in health organizations across diverse contexts.

METHODS:
Following PRISMA guidelines(6) and a registered protocol (PROSPERO CRD42025202181), we searched PubMed, Scopus, Web of Science, and PsycINFO from inception through October 2025. Eligible studies examined definitions, determinants, measurement instruments or interventions addressing trust or mistrust in healthcare organizations. Study selection, data extraction, and quality appraisal were conducted independently by multiple reviewers using the KMET checklist for empirical studies and the JBI tool for non-empirical designs.

RESULTS:
We included 149 studies (2003-2025) from 52 countries. Most (91.3%) provided explicit definitions; recent studies increasingly conceptualised mistrust as a distinct, values-based construct rooted in structural and historical inequity. Determinants were identified across three levels, with individual (88.6%), organizational (73.1%), and contextual/systemic (79.2%) factors frequently reported. While 29.5% of studies used validated instruments, 68% of these were from U.S. settings; methodological heterogeneity and limited cross-cultural validation remained substantial. Thirty-seven studies (24.8%) evaluated interventions, grouped into five domains. Community engagement and governance reforms showed the greatest promise for strengthening trust, although evaluations were typically short-term and rarely assessed equity-related outcomes. Evidence originated predominantly from high-income countries (71.8%).

CONCLUSIONS:
Trust operates as a determinant and an indicator of equitable health-system performance. Advancing the field requires culturally adaptable, validated measures and interventions that address the structural and historical foundations of mistrust, particularly among marginalized populations. Long-term investment in transparent governance, participatory communication, equitable service delivery, and accountable digital infrastructures is critical to fostering trusted and resilient health systems.