Cat density and Toxoplasma gondii linked to national happiness levels

A study published in PLOS One by an international team of researchers has identified correlations between domestic cat density and national happiness levels across 93 countries. The research, involving institutions from the United States, Mexico, Finland, and Latvia, examined whether biological and ecological factors influence well-being alongside traditional socioeconomic indicators like GDP and healthcare spending.

The findings suggest that countries with higher densities of domestic cats tend to report higher levels of happiness. Conversely, countries with higher exposure to the parasite Toxoplasma gondii—a microorganism for which felines are a primary host—tended to report lower happiness scores. While T. gondii is often asymptomatic, it has been linked to mental health conditions such as anxiety, depression, and schizophrenia.

Researchers noted several complexities in the data. For instance, countries with more cats often showed lower levels of T. gondii exposure, which was unexpected. The authors emphasized that these are country-level correlations and do not prove direct causation, stating, “we cannot say that having more cats makes people happier nor that Toxoplasma makes people less happy.” The study suggests that understanding human happiness may require looking beyond economic metrics to include the relationships between humans, animals, and their environments.