Parasite tied to self-harm, suicide attempts

Women who are infected with a common parasite may be more likely to hurt themselves or attempt suicide, a new study of over 45,000 new mothers in Denmark suggests.

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 behaviour.

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.

All of the infants were tested for antibodies against the parasite through a blood sample drawn five to 10 days after birth. Because the babies were still too young to make their own antibodies, any that showed up in their blood would have been passed from mothers.

Just over one-quarter of the babies were positive for T gondii antibodies, meaning their mothers likely had a chronic, underlying toxoplasmosis infection.

And over the next 11 to 14 years, infected women were about 50 per cent more likely to cut, burn or otherwise hurt themselves, according to their medical records, and 80 per cent more likely to attempt suicide.

In total, 488 women hurt themselves for the first time during the study or eight out of every 10,000 annually and 78 tried to kill themselves.

"That's not a very high risk, when you come down to it," said Dr Louis Weiss, who studies toxoplasmosis at Albert Einstein College of Medicine in New York.

Still, he told Reuters the findings are "really quite interesting". Part of the study's strength, he added, comes from its size and how long it followed the Danish women.

"There probably is an effect of this parasite on human behaviour, which has been suspected," based on studies of animals infected with toxoplasmosis, said Weiss, who wasn't involved in the new research.


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