Household Infection Leads to Suicide?
By on July 3rd, 2012

Scientists at the University of Maryland have observed the association of a curious factor with suicidal behaviour in women- infection by the parasite Toxoplasma gondii.

Identifying ‘Hosts’ for the Parasite

This study involved some deep digging into the past. These researchers looked up 45,700 Danish women who were known to have been infected with the virus during childbirth. They then scoured nationwide health registries in Denmark to investigate suicidal rates amongst these women. The free health-care offered by the government made such medical histories available. Shockingly, they found that suicide rates among women who had been infected with the virus were one and a half times higher than amongst women who were uninfected.

The reasoning behind this study was that victims of suicide are found to have a higher immune system activity than normal. This led Dr. Postolache, who led this research, to wonder if an infection might be involved in any way.

The ‘Cat Lady’ Parasite is Quite Prevalent

This discovery is making news, particularly because about one-third of the world’s population plays host to the parasite. It is spread by cat faeces and unwashed vegetables and meat. Once inside the host, the parasite hides in cysts of the brain and muscles and patients often don’t suffer any symptoms.  This parasite, in fact, has also been linked to schizophrenia.

Image sourced from

This parasite may not be as innocuous as it looks.

Not a Conclusive Link

The research team behind this discovery is warning everyone against jumping the gun. More research has to be done to validate this putative link. This study only focussed on women with children (because of the availability of data) and couldn’t take cases of attempted suicide. Moreover, there are no studies that confirm presence of T.gondii in individual cases of suicides until now.

There is also the possibility of mixing up correlation with causation. “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,” Dr. Postolache says.

This link will likely set off a hunt for the intermediate molecular mechanisms linking infection by the virus, suicide risk factors and suicide itself. Neuroimmunology could bring a new dimension to the psychological study of suicidal behaviour.


Author: Shweta Ramdas
Beginning life as a grad student studying human genetics.

Shweta Ramdas has written and can be contacted at

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