The infection, known as toxoplasmosis, is caused by the parasite Toxoplasma gondii. Humans can become chronically infected by eating undercooked meat or unwashed vegetables or by handling cat litter, as the parasite is known to multiply in the gut of infected cats.
Toxoplasmosis is often symptom-free, but can be dangerous in people with weak immune systems or during pregnancy, since the parasite may be passed to babies.
Some studies have linked the parasite to a higher chance of developing schizophrenia, and researchers believe because the T. gondii parasite lives in the brain, it could have an effect on emotions and behavior.
For the new report, Dr. Teodor Postolache from the University of Maryland School of Medicine in Baltimore and his colleagues used Danish medical registries to track 45,788 women who were originally included in a study that screened newborn babies for toxoplasmosis.