A study published in the July 2012 issue of the Archives of General Psychiatry has found an association between Toxoplasma gondii infections and history of suicide attempts. The study followed 45,788 Danish women who had children between 1992 and 1995. The study lasted for more than ten years.
During that time period, only 78 women tried a violent suicide attempt. That makes infected women 81% more likely to attempt suicide than non-infected women. The risk increases with increasing IgG antibody levels to T. gondii. The study’s authors want to emphasize that the risk of very small, and this study doesn’t prove a link between T. gondii infections and suicide, but means that further studies should be conducted.
Another study found a significant relationship between T. gondii infections, along with other infectious agents, and suicidal self-directed violence in younger patients who had an increased risk of schizophrenia.
Toxoplasmosis gondii infections are typically contracted through coming into contact with infected cat litter, by eating infected raw or undercooked meat, and by drinking water contaminated with the oocysts. In fact, a recent study found that organic meats may carry an increased risk of toxoplasmosis. The infection can be passed from a pregnant women to her fetus, which can lead to brain damage, retardation, and blindness in the baby.
Suicide claims the life of about one million people around the world every year. For each death, 10 to 20 people make suicide attempts. And about one-third of people worldwide are infected with the T. gondii parasite. Most do not know they are infected, since symptoms are rare.
The study’s authors say that there is a “predictive association” between T. gondii IgG antibody levels in the blood of women who have just given birth and self-directed violence in later life. Two previous studies, one conducted in Maryland and another in Turkey, found the same association. A history of mental illness did not alter the study’s findings.
The possible mechanism for this association is through the immune system and the brain. Concentrations of kynurenic acid in the brain and spinal fluid are associated with violent suicide attempts; an increase in that particular acid was found in mice infected with T. gondii. The study’s authors would like to see future studies on this topic that may lead to new types of suicide prevention, including talk therapy and drug therapy.