Using Systems Thinking to Address Diet, Food Systems and Mental Health in a Caribbean Small Island Developing State

Small island developing states face distinct vulnerabilities driving a nutrition transition toward ultra-processed imports. While global evidence links food security and diet to mental health, Caribbean research remains limited and linear. This study maps dynamic feedback loops governing the food system–mental health nexus in St. Lucia to identify potential leverage points for intervention. Qualitative data were translated into a preliminary causal loop diagram, which was refined using literature triangulation and a group model refinement workshop with multisectoral stakeholders, and finally benchmarked against the World Health Organization’s Food Systems Delivering Better Health guide. Four major feedback loops included diet choices and health; local foods and cultural identity; food security and purchasing behaviours; and farming and community. Local food consumption, market shopping and food sharing build social capital, cultural pride and psychological resilience. Conversely, reliance on imported processed foods, food insecurity, and systemic agricultural shocks exacerbate mental distress. Participants proposed multisectoral interventions spanning the socioecological model of health. Interventions should target these systems-informed structural drivers to effectively safeguard population mental health. However, the potential utility of interventions cannot be established without quantitative testing, such as modelling to test leverage points amidst surrounding constraints.