ABSTRACT
BACKGROUND: Improving the adoption and implementation of policies to curb non-communicable diseases (NCDs) is a major challenge for better global health. The adoption and implementation of such policies remain deficient in various contexts, with limited insights into the facilitating and inhibiting factors. These policies have traditionally been treated as technical solutions, neglecting the critical influence of political economy dynamics. Moreover, the complex nature of these interventions is often not adequately incorporated into evidence for policy-makers. This study aims to systematically review and evaluate the factors affecting NCD policy adoption and implementation. METHODS: We conducted a complex systematic review of articles discussing the adoption and implementation of World Health Organization's (WHO's) "best buys" NCD policies. We identified political economy factors and constructed a causal loop diagram (CLD) program theory to elucidate the interplay between factors influencing NCD policy adoption and implementation. A total of 157 papers met the inclusion criteria. RESULTS: Our CLD highlights a central feedback loop encompassing three vital variables: (1) the ability to define, (re)shape, and pass appropriate policy into law; (2) the ability to implement the policy (linked to the enforceability of the policy and to addressing NCD local burden); and (3) ability to monitor progress, evaluate and correct the course. Insufficient context-specific data impedes the formulation and enactment of suitable policies, particularly in areas facing multiple disease burdens. Multisectoral collaboration plays a pivotal role in both policy adoption and implementation. Effective monitoring and accountability systems significantly impact policy implementation. The commercial determinants of health (CDoH) serve as a major barrier to defining, adopting, and implementing tobacco, alcohol, and diet-related policies. CONCLUSION: To advance global efforts, we recommend focusing on the development of robust accountability, monitoring, and evaluation systems, ensuring transparency in private sector engagement, supporting context-specific data collection, and effectively managing the CDoH. A system thinking approach can enhance the implementation of complex public health interventions.