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Thursday 20th June 2019

Cat litter parasite linked to self-harm

9th July 2012

A study of new mothers in Denmark has found a link between infection with a common parasite and self-harming behaviours or suicidal tendencies.


Women who carry the toxoplasmosis parasite, known as Toxoplasma gondii, may be more likely to hurt or kill themselves, according to researchers at the University of Maryland School of Medicine in Baltimore.

The parasite is found in soil, unwashed vegetables or undercooked meat, as well as in the faeces of infected cats, in whose intestines it thrives.

Toxoplasmosis often causes no symptoms, but can be passed on to babies during pregnancy and can be harmful to people with compromised immune systems.

The parasite has also been linked by previous studies to a higher chance of developing schizophrenia.

It resides in the brain, making a possible link between toxoplasmosis and changes in emotion and behaviour.

The research team led by Teodor Postolache analysed Danish medical registries to assess 45,788 women who were originally included in a study that screened infants for toxoplasmosis.

They found that more than a quarter of the babies in the study tested positive for antibodies against toxoplasmosis, which indicated that their mothers probably had a chronic infection, as babies of that age inherit their antibodies from their mothers.

Compared with the group who were not infected, the infected group were 50% more likely to burn, cut or otherwise harm themselves over the next 11-14 years, based on their medical records alone.

More worryingly, they were 80% more likely to attempt suicide.

A total of 78 women attempted suicide during the period of the study, while 488 women self-harmed. However, only 18 women actually managed to commit suicide.

According to toxoplasmosis expert Louis Weiss of the Albert Einstein College of Medicine in New York, the overall risk was still not very high.

But he said the findings were "interesting," because the study had included data from large numbers of women over a long period of time.

He said previous studies had shown that the parasite affects animal behaviour, so an impact on human behaviour was not totally surprising.

According to Postolache and his team, who published their findings in the Archives of General Psychiatry, it is hard to infer a causal link between toxoplasmosis and self-harming or suicidal behaviour.

But it is possible, he said, that the parasite could directly affect brain chemistry, changing the composition of neurotransmitters that govern mood and behaviour.

Inflammation caused by the chronic infection could also cause brain inflammation, which might affect brain chemistry in a subtle way.

He said people should not shun cats as a result, as many infections came from the outdoor environment and were passed on by cats roaming freely and not under anyone's control.


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