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.