Wealth, health, cats and Toxoplasma gondii: An ecological correlational study of subjective well-being across 93 countries

National happiness is related not only to socioeconomic factors but also to biological and ecological factors. This ecological correlational study examined associations between national happiness, cat density, Toxoplasma gondii exposure, and socioeconomic indicators across 93 countries. We hypothesized that countries with higher socioeconomic indicators (e.g., GDP, health expenditure, income level) would exhibit higher happiness levels. In contrast, we predicted that higher T. gondii exposure, both acute (IgM) and chronic (IgG), would be negatively associated with national happiness. Data on happiness measures, cat density, GDP per capita, income classification, health expenditure, and T. gondii seroprevalence in pregnant women (as a proxy for broader population exposure) were obtained from publicly available sources. In line with our hypothesis, we found that national happiness was positively associated with cat density and some socioeconomic factors and negatively associated with IgM seroprevalence. In multivariate analyses, cats per 10,000 inhabitants and IgM seroprevalence remained the strongest independent predictors. Overall, these exploratory analyses suggest that biological and ecological factors are associated with socioeconomic variables in determining national well-being. Future studies of happiness at the national level should integrate both socioeconomic and biological perspectives and include longitudinal and interdisciplinary approaches to elucidate the underlying mechanisms and processes.