Countries with more domestic cats tended to report higher levels of national happiness, while countries with greater exposure to the parasite Toxoplasma gondii tended to report lower happiness, according to a new peer-reviewed analysis spanning 93 countries.
The finding is intriguing because cats sit on both sides of the study’s central puzzle. Companion animals may be linked to social connection and emotional well-being, yet cats are also the definitive host of T. gondii, a widespread parasite that can infect humans. The researchers therefore asked whether cat density, parasite exposure and socioeconomic conditions might each be associated with how nations score on subjective well-being.
The answer was not a simple story about pets making people happier. National happiness correlated strongly with cat density, but it correlated even more strongly with income and gross domestic product. The study was ecological and cross-sectional, meaning it compared countries rather than individual cat owners. It cannot establish that owning a cat causes happiness, that happier societies acquire more cats, or that either relationship is causal.
A global dataset linking well-being, wealth, cats and infection
Javier I. Borráz-León and colleagues assembled publicly available data for 93 countries with complete information across the variables they wanted to compare. National happiness came from the 2025 Happiest Countries dataset, which reflects three-year averages covering 2022 to 2024. Domestic cat populations were standardized as cats per 10,000 inhabitants. GDP per capita came from World Bank data, income groups followed World Bank classifications, and health expenditure was measured as a share of GDP using World Health Organization data.
Measuring T. gondii exposure across dozens of countries was harder. Because comparable general-population data were unavailable, the researchers used seroprevalence estimates from pregnant women as a proxy for broader community exposure. IgM antibodies were used as an indicator of more recent infection, while IgG antibodies represented past or chronic exposure. Both measures were grouped into five prevalence categories.
The team first examined bivariate correlations and then built an exploratory regression model. Variables that were not normally distributed were log-transformed. Because GDP and income were extremely highly correlated with each other, with a correlation of 0.93 and variance inflation factors above 7, both were removed from the final regression to reduce multicollinearity. Health expenditure remained as the socioeconomic indicator alongside cat density, IgM and IgG seroprevalence.
The researchers also ran a mediation analysis using 5,000 bootstrap samples. Importantly, they describe this as a statistical decomposition of associations, not evidence of a causal pathway.
Cat density showed a sizeable relationship with happiness
Across the 93 countries, cat density correlated positively with national happiness at r = 0.620, with a 95% confidence interval from 0.480 to 0.733 and p < 0.001. That is a substantial country-level association.
But conventional economic indicators were even more strongly related to happiness. GDP per capita correlated with happiness at r = 0.800, while national income level correlated at r = 0.780. Health expenditure had a smaller positive correlation of r = 0.350. All three associations had p-values below 0.001.
Cat density itself was closely tied to prosperity. It correlated with GDP at r = 0.790, income level at r = 0.770, and health expenditure at r = 0.600. This matters because a country with more cats per person may differ from a country with fewer cats in many other ways, including disposable income, housing, veterinary care, sanitation, urbanization and cultural attitudes toward companion animals.
Toxoplasma exposure pointed in the opposite direction
The parasite results moved in the opposite direction. National happiness was negatively correlated with recent or acute T. gondii exposure measured through IgM seroprevalence at r = -0.540, with a 95% confidence interval from -0.672 to -0.380 and p < 0.001. The association with IgG seroprevalence was weaker but still negative at r = -0.330, 95% CI -0.504 to -0.141, p = 0.001.
Wealthier countries also tended to show less parasite exposure. GDP correlated with IgM seroprevalence at r = -0.590 and with IgG at r = -0.330. Income level showed a similar pattern.
One counterintuitive result was that more cats did not correspond to more chronic parasite exposure. Cat density and IgG seroprevalence had a small negative correlation of r = -0.200, although it narrowly missed the conventional threshold for statistical significance at p = 0.058. The authors suggest that differences in how cats live may help explain the pattern. Cats in wealthier countries may be more likely to live indoors, receive veterinary care and eat commercially prepared food, while free-roaming populations and environmental exposure may differ elsewhere. That explanation remains a hypothesis rather than a result directly tested by the study.
The combined model explained 47% of the variation in happiness
After GDP and income were removed because of multicollinearity, the regression model included cat density, health expenditure, IgM and IgG seroprevalence. Together, these variables accounted for 47.0% of the variance in national happiness scores, with R² = 0.470 and F(4,88) = 19.500, p < 0.001.
Within that model, cat density had the strongest positive standardized association with happiness at β = 0.520, p < 0.001. IgM seroprevalence had a significant negative association at β = -0.240, p = 0.021. Health expenditure and IgG showed smaller, non-significant associations once the variables were considered together.
The mediation analysis produced a positive direct effect between cat density and happiness of β = 0.104, a bootstrapped indirect effect through IgM of β = 0.034, and a total effect of β = 0.139. Again, those paths describe how variables co-vary in the dataset. They do not demonstrate that cats alter parasite exposure and thereby change happiness.
Why the result is interesting without being causal
The study’s value lies less in the idea that cats are a route to national happiness and more in the way it combines variables usually studied separately. Measures of well-being are often discussed through economics, health systems and social conditions. The new analysis asks whether human-animal relationships and infectious-disease ecology may also carry useful information about the environments in which people live.
A high cat density could partly reflect conditions associated with affluent societies, such as greater disposable income, housing that permits companion animals, veterinary infrastructure and cultural acceptance of pets. Cats may also provide companionship, although this dataset cannot tell whether people in cat-dense countries personally receive those benefits. Conversely, parasite exposure can be shaped by sanitation, food preparation, climate, free-roaming animals and healthcare access.
This distinction is especially important because country-level associations can produce an ecological fallacy when they are applied to individuals. The data do not show that a person who owns a cat is happier than a person who does not. They also do not establish an individual’s T. gondii status or mental health. Research Today recently covered another example of why broad behavioural measures need careful interpretation, finding that how people use social media may matter as much as screen time for mental health. In both cases, the context around an exposure can matter as much as the headline measure itself.
Important limitations
The authors identify several reasons for caution. First, T. gondii seroprevalence was estimated from pregnant women rather than nationally representative samples of entire populations. Routine testing makes this group useful for international comparisons, but exposure patterns, healthcare access and testing practices can differ between pregnant women and the wider population.
Second, the cat-density measure combines pet, stray and feral cats. Those populations may have very different relationships with companionship, veterinary care, hunting, food sources and parasite transmission. A country with many indoor pets is not biologically or socially equivalent to one with a large free-roaming cat population.
Third, potentially important confounders such as urbanization, sanitation infrastructure, temperature and humidity were not included. Climate can affect the survival and sporulation of T. gondii oocysts, while sanitation and urban structure can influence both animal populations and human exposure.
Fourth, the study used cross-sectional data assembled from different sources and time periods. That introduces temporal mismatch and prevents researchers from establishing which variable came first. Reverse causation and unmeasured confounding remain plausible.
Finally, the happiness index itself partly incorporates socioeconomic information, including GDP-related conditions. That creates some conceptual overlap when happiness is compared with economic predictors. The 93 countries were also selected because complete data were available, rather than through random sampling. The authors note that the sample had about 85% power to detect a moderate correlation of r = 0.3 but was underpowered for small effects below roughly r = 0.20.
What the study adds
The research does not offer a prescription to adopt more cats, nor does it suggest that cats themselves are responsible for national differences in well-being. Instead, it highlights a potentially informative intersection between prosperity, companion-animal ecology, infectious disease and subjective well-being.
The next step would be stronger longitudinal and individual-level research that distinguishes owned, stray and feral cats, measures human-cat interaction directly, uses representative parasite testing, and follows well-being over time. Such work could help determine whether cat density is merely a marker of broader social conditions or whether human-animal relationships contribute independently to population well-being.
Source Information
Study: Borráz-León, J. I., Rantala, M. J., Krams, I., & Maestripieri, D. (2026). Wealth, health, cats and Toxoplasma gondii: An ecological correlational study of subjective well-being across 93 countries.
Journal: PLOS One, 21(9), e0357911.
Published: 30 September 2026.
DOI: 10.1371/journal.pone.0357911
Study design: Ecological correlational study using publicly available country-level data from 93 countries.
Funding and competing interests: The authors reported no specific funding and declared no competing interests.
Data availability: The authors state that the study dataset is included in the supplementary material and is also available through the Open Science Framework.
