Abstract
INTRODUCTION: Colorectal cancer (CRC) is one of the leading causes of cancer-related morbidity and mortality worldwide. Although early detection through screening significantly reduces mortality, adherence to recommended screening remains suboptimal. This systematic review examines the multilevel factors influencing CRC screening adherence, and integrates the findings within the Socio-Ecological Model to provide a structured analytical framework. METHODS: A systematic search was conducted across PubMed, Scopus, and Web of Science for studies published between 2000 and 2024 that employed multilevel modeling to examine CRC screening behavior. Eligible studies involved average-risk adults and reported both individual- and contextual level determinants of screening adherence. Studies focusing exclusively on clinical predictors or non-screening outcomes were excluded. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Tools. A narrative synthesis was performed to identify key individual, interpersonal, community, institutional, and policy-level determinants of CRC screening adherence. RESULTS: Nine studies met the inclusion criteria, predominantly from high-income settings. At the individual level, older age, female sex, higher socioeconomic status, and health insurance coverage were consistently associated with greater screening adherence. Community factors such as neighborhood socioeconomic status and healthcare accessibility, influenced screening behavior, while institutional elements included system structures and service availability. Policy-level determinants, such as national health insurance and national screening guidelines, were less frequently examined but demonstrated measurable effects. Despite heterogeneity in populations, synthesis within the Socio-Ecological Model highlighted the interconnected nature of these determinants and emphasized the need for multilevel interventions targeting individual, social, and structural determinants. CONCLUSION: This review emphasizes the importance of addressing CRC screening behavior through a multilevel perspective that incorporates individual, social, and structural determinants. Future research should explore these determinants in low- and middle-income settings and assess the effectiveness of integrated multilevel interventions in improving CRC screening adherence.