From Unrealistic to Functional Optimism in Illness Perception: A Psychometric Comparison Across 10 Countries.

People's perceptions of illness and its risks influence health behaviors, including risk management and precautionary measures. Illness perception often involves unrealistic optimism, reducing infection risk perception. However, crises disrupt self-regulation and optimism due to uncontrollable situations. This study examines optimism's link to risk and illness perception during the first COVID-19 wave in 10 countries, with 7254 participants (48.1% women, mean age = 40, SD = 14.8). We used Bayesian structural equation modeling for psychometric stability and one-way ANOVAs for country comparisons. Multiple regression analyses examined the impact of optimism and demographic variables on illness perception. Significant cross-country variations emerged in illness perception and optimism. In terms of the relationship between variables, optimism correlated with increased COVID-19 risk perception, especially for negative outcomes, concern, and consistency. During crises, optimism shifted from unrealistic to functional, promoting treatment adherence, personal control, and coherence. These dimensions represent individuals' beliefs in managing illness, highlighting optimism's adaptive role in crises.