Game theory and environmental health behavior: a population model of sunscreen use, social norms, and melanoma incidence

Introduction: Melanoma is a largely preventable yet economically significant cancer, particularly in high-UV regions. Despite strong evidence that sunscreen reduces melanoma risk, its use remains suboptimal due to misaligned private and social incentives. Methods: We develop an evolutionary game-theoretic model in which individuals choose between sunscreen use and non-use. Payoffs incorporate private benefits, costs, and externalities from shared healthcare financing. The model is calibrated using Australian data. Results: Behavior is driven by private incentives. When private benefits are lower than costs, populations converge to non-adoption, even when sunscreen use is socially optimal. Calibration shows this divergence arises in high-risk populations. Discussion: Sunscreen use represents a public goods problem with under-adoption driven by externalities. Policies such as subsidies, mandates, and social norm interventions are required to align incentives and improve public health outcomes.