Overview
- An international team published in PLOS One analyzed public data from 93 countries to compare national happiness scores, domestic cat density, and Toxoplasma gondii exposure.
- The researchers found a positive association between cat density and reported national happiness that held after adjusting for several socioeconomic factors.
- They also found a separate negative association between national rates of Toxoplasma gondii exposure and happiness; T. gondii is a common parasite that can form silent cysts in human brain and muscle tissue and has been linked in prior studies to mood and neuropsychiatric differences.
- Unexpectedly, countries with more cats tended to have lower T. gondii exposure, a pattern the authors attribute to wealth and pet-care practices such as indoor living, commercial feeding, and routine veterinary care that reduce parasite transmission.
- The study is ecological and cannot show cause and effect, so the authors and reporters call for individual-level, longitudinal and interdisciplinary studies to test whether pet ownership, parasite infection, or shared socioeconomic conditions drive the associations and what public-health actions might follow.