By GRAHAM SMITH
PUBLISHED: 03:52 EST, 3 July 2012 | UPDATED: 03:52 EST, 3 July 2012
- Women infected with Toxoplasma gondii are one-and-a-half times more likely to attempt suicide
- Third of world’s population is infected with parasite, which hides in cells in the brain and muscles, often without producing symptoms
Female cat owners are more likely to suffer mental health problems and commit suicide because they can be infected with a common parasite that can be caught from cat litter, according to a study.
Women infected with the Toxoplasma gondii – or T. gondii – parasite, which is spread through contact with cat faeces or eating undercooked meat or unwashed vegetables, are at increased risk of suicidal thoughts.
About a third of the world’s population is infected with the parasite, which hides in cells in the brain and muscles, often without producing symptoms.
Risk? Female cat owners are more likely to commit suicide because they can be infected with a common parasite that can be caught from cat litter
The infection, which is called toxoplasmosis, has been linked to mental illness, such as schizophrenia, and changes in behaviour.
Scientists from the U.S., Denmark, Germany and Sweden looked at more than 45,000 Danish women who gave birth between 1992 and 1995.
Babies don’t produce antibodies to T. gondii until three months after they are born, so the antibodies present in their blood represented infection in the mothers.
The scientists scoured Danish health registries to determine if any of women diagnosed as infected later attempted suicide, including cases of violent suicide attempts which may have involved guns, sharp instruments and jumping from high places.
They found that women infected with T. gondii were one-and-a-half times more likely to attempt suicide compared to those who were not infected, and the risk seemed to rise with increasing levels of the T. gondii antibodies.
Lead researcher Dr Teodor Postolache, from the University of Maryland, said: ‘We can’t say with certainty that T. gondii caused the women to try to kill themselves, but we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies.’
Toxoplasma gondii thrives in the intestines of cats and is spread through oocysts passed in their faeces
The study is the largest ever to try and ascertain a link between T. gondii and attempted suicide and the first prospective study to document suicide attempts that occurred after the infection was discovered.
Dr Postolache’s research team at the University of Maryland was the first to report a connection between T. gondii and suicidal behaviour in 2009.
The parasite thrives in the intestines of cats and is spread through oocysts passed in their faeces.
All warm-blooded animals can become infected through ingestion of these oocysts. The organism spreads to their brain and muscles, hiding from the immune system within ‘cysts’ inside cells.
Humans can become infected by changing their infected cats’ litter boxes, eating unwashed vegetables, drinking water from a contaminated source or, more commonly, by eating undercooked or raw meat that is infested with cysts.
Not washing kitchen knives after preparing raw meat before handling another food item also can lead to infection.
Pregnant women can pass the parasite directly to their unborn babies and are advised not to change cat litter boxes to avoid possible infection.
Dr Postolache noted the study’s limitations, such as the inability to determine the cause of suicidal behaviour.
He added: ‘T. gondii infection is likely not a random event and it is conceivable that the results could be alternatively explained by people with psychiatric disturbances having a higher risk of becoming T. gondii infected prior to contact with the health system.’
The findings are published online in the Archives of General Psychiatry.