Cats, Parasites and Happiness: New Global Study Links Felines to National Well-Being

National happiness has long been measured against familiar yardsticks: gross domestic product, household income, health expenditure and life expectancy. A new study published on September 30, 2026 in the open-access journal PLOS One suggests that the picture of collective well-being may be incomplete without considering an unexpected variable: the domestic cat. Javier I. Borráz-León of the Secretariat of Science, Humanities, Technology, and Innovation in Mexico City and colleagues analyzed data from 93 countries and found that both cats and the parasites they carry are strongly correlated with national happiness scores, in ways that pull in opposite directions. The findings do not overturn the importance of wealth and health, but they add a biological and ecological dimension to a field that has traditionally been dominated by socioeconomic indicators.

The researchers set out to examine whether factors rarely explored in happiness research might underlie some of the variation in how countries score on subjective well-being measures. National happiness scores, which aggregate how satisfied people report being with their lives, are well documented to track economic conditions such as family income and the costs of health care. Yet these economic variables cannot fully explain why some nations consistently report higher well-being than others with comparable resources. To probe this gap, the team compiled country-level data on income, health costs, GDP, the density of domestic cats, and the prevalence of Toxoplasma gondii, a single-celled parasite that reproduces in cats and can be transmitted to humans.

The results were striking in their asymmetry. Countries with greater numbers of cats tended to report higher levels of national happiness, a pattern consistent with a substantial body of research on the emotional and psychological benefits of pet ownership. At the same time, countries with higher prevalence of Toxoplasma gondii infection tended to report lower levels of happiness, even though the parasite is spread by the very animals associated with the positive effect. This counterintuitive divergence, the authors argue, points to complex factors at work rather than any simple causal chain running from cats to contentment or from parasites to misery.

The dataset included China, which offers a concrete illustration of the patterns the researchers observed. In the data used by the team, China reported a happiness index just above the average for the countries included in the study, at 5.97 versus an average of 5.72. Its cat density was relatively low, with 376 cats per 10,000 people compared to an average of 989, while its IgM seroprevalence levels for T. gondii fell at the average, with both measures categorized as level 3 on a five-level scale. Such country-level snapshots underscore that the relationships among cats, parasites and happiness vary considerably across nations and cannot be reduced to a single global trend.

The authors are careful to emphasize what the study does and does not show. As an ecological correlational analysis, it compares aggregate figures across countries rather than tracking individuals, so it cannot establish that owning cats makes people happier or that Toxoplasma infection makes them less happy. In their own words: “What we found is that countries with more cats tended to report higher levels of happiness, while countries with higher exposure to Toxoplasma gondii tended to report lower levels of happiness. Of course, these are associations at the country level, so we cannot say that having more cats makes people happier or that Toxoplasma makes people less happy, but the patterns are interesting enough to deserve further investigation.”

One plausible mechanism, the authors suggest, runs through economic conditions. Higher national income and better public health infrastructure might simultaneously encourage pet ownership and reduce infection rates, since wealthier societies often have greater access to veterinary care, parasite control and sanitation. In this view, cats are not themselves the cause of happiness but a visible marker of the prosperity and health systems that foster both companion animals and lower parasite exposure. The negative association between Toxoplasma prevalence and happiness could then reflect the same underlying socioeconomic gradient rather than any direct effect of the parasite on mood at the population level.

Perhaps the most surprising result was the relationship between the two biological variables themselves. “One of the most surprising findings was that countries with more cats did not show greater exposure to Toxoplasma gondii; in fact, the association went in the opposite direction,” the authors note. “This highlights an important point: the relationship between humans, animals, and infectious diseases depends not simply on the presence of animals, but also on the social, economic, and environmental conditions in which those interactions occur.” In other words, cat density alone does not determine how much parasite exposure a population experiences; hygiene, food safety, climate and public health practices all shape transmission pathways independently of how many cats live in a country.

For the researchers, the broader significance of the work lies in its integration of research traditions that rarely intersect. “What we find most interesting is that these results bring together factors that are usually studied separately: wealth, health, human–animal relationships, and infectious disease,” the authors explain. “Our study suggests that understanding why some populations report greater well-being may require us to consider biological and ecological factors alongside the socioeconomic conditions that have traditionally received most attention.” This framing positions the study as an invitation to widen the analytical lens of happiness research, which has historically centered on economics and public health statistics while leaving ecology and zoonotic disease largely unexamined.

The study, titled “Wealth, health, cats and Toxoplasma gondii: An ecological correlational study of subjective well-being across 93 countries,” was conducted by an international team spanning Mexico, Finland, Latvia and the United States, and received no specific external funding. The authors declare no competing interests. As an observational study, it demonstrates that biological factors, and not only economic ones, can correlate with happiness, revealing new avenues for investigating national well-being. The authors caution that while the analysis unveils previously unrecognized relationships, future studies will be needed to determine the underlying mechanisms, ideally through designs that can test individual-level effects rather than country-level associations.

For now, the message for the public is one of measured curiosity rather than practical prescription. Nothing in the data suggests that adopting a cat will raise a nation’s happiness score, nor that cat populations should be managed to control Toxoplasma exposure as a well-being policy. What the study does offer is a reminder that the determinants of how societies feel may be stranger and more interconnected than the standard dashboards of GDP and health spending imply. The companionship of animals, the ecology of parasites and the prosperity of nations appear to be woven together in patterns that scientists are only beginning to untangle, and the humble house cat has turned out to be an unexpected thread in that fabric.

Subject of Research: Ecological correlational study of cats, Toxoplasma gondii prevalence and national happiness across 93 countries

Article Title: Wealth and health aren’t the only indicators of national happiness – there’s also cats!

Article References: Wealth and health aren’t the only indicators of national happiness – there’s also cats!. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: national happiness, cats, Toxoplasma gondii, subjective well-being, parasites, PLOS One, pet ownership, GDP, public health, ecological study, cross-country analysis, zoonotic disease