What Cat Litter & Suicide Have in Common

Toxoplasmosis parasite linked to higher risk of suicide and self violence

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Among the various things pregnant women generally should avoid is changing kitty litter, which may seem oddly random in a list with alcohol, undercooked meat, soft cheeses and smoking.

But toxoplasmosis, a condition caused by a parasite that can be found in cat feces, as well as undercooked meat or unwashed vegetables, is a serious disease.

A recent study has found that women infected with it are at a higher risk for committing suicide.

"Avoid undercooked meats and unwashed vegetables."

Marianne G. Pedersen, MSc, of the Department of Economics and Business at the National Centre for Register-Based Research at Aarhus University in Denmark, looked at the link between the Toxoplasma gondii (T. gondii) parasite and self-directed violence.

The study group included 45,788 women whose babies' antibodies for the parasite were measured when the women gave birth between 1992 and 1995. If a newborn has antibodies, it means the mother was infected.

The researchers followed the women for up to 14 years and found that those who had T. gondii were twice as likely to attempt suicide and about 1.5 times more likely to try to hurt themselves in some other way compared to women who were not infected with the parasite.

The more antibodies a woman had - indicating a higher level of infection from the parasite - the higher the risk for suicide or self-violence was.

These women with toxoplasmosis were also 1.8 times more likely to attempt a violent suicide, such as one involving a gun, knife or high jump rather than an overdose, and 1.5 times more likely to repeatedly injure themselves intentionally.

Toxoplasmosis has already been linked to schizophrenia and other mental illnesses in past studies. This study took into account previous mental illness in the women and their parents and still found the association between toxoplasmosis and self-violence.

The parasite that causes it lives in the brain or muscle cells of about one third of the world's population, though it often causes no symptoms.

The most common ways to contract the T. gondii parasite are by eating undercooked meats, eating unwashed vegetables, drinking contaminated water or coming into contact with cat poop, since the parasite lives in cats' intestines.

Pregnant women who get toxoplasmosis can pass the parasite on to their developing baby, which is the reason for the warnings about cat litter and undercooked meat.

"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," said senior author Teodor T. Postolache, MD, an associate professor of psychiatry and director of the Mood and Anxiety Program at the University of Maryland School of Medicine.

The study was limited by only being able to study pregnant women, by the challenges in determining why someone might be suicidal and by the fact that there may have been suicide attempts that were undetected or unreported in the women's records.

"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," said Dr. Postolache.

The researchers said it's not clear what the connection may be between the parasite and suicide attempts, and it may even be that people who are otherwise predisposed to commit suicide may be more likely to have become infected with T. gondii in the first place.

The study was published July 2 in the Archives of General Psychiatry. The research was funded by the Stanley Medical Research Institute and the American Foundation for Suicide Prevention. The authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
July 2, 2012
Last Updated:
December 5, 2012