According to Time
, the latest finding that Toxoplasma infection increases risk of violent suicide attempt in women comes from a study of 45,788 Danish women who gave birth between May 15, 1992 and January 15, 1995. In the study titled "Toxoplasma gondii Infection and Self-directed Violence in Mothers,"
the University of Maryland School of Medicine researchers tested the women's babies for T. gondii antibodies which they could only have acquired from their mothers, and then compared infection rates to the women's suicide rates reported in the Danish health resgistry. The study also checked the mental health registry to see if the same women had been previously diagnosed with mental illness.
The team of researchers led by Dr. Teodor T. Postolache, associate professor of psychiatry and director of the Mood and Anxiety Program at the University of Maryland School of Medicine, found from a study
of the data obtained from Danish registries that women infected with T. gondii were one-and-half times more likely to attempt suicide than those who were not infected. The suicides involved violent attempts with guns, sharp instruments and jumping from a height. The study found that the risk of suicide appeared to increase with increasing levels of T. gondii antibodies.
reports that the illness resulting from infection with Toxoplasma gondii, called toxoplasmosis, has been linked to mental illnesses such a schizophrenia in previous studies. The Time
reports that previous studies on T. gondii infection in humans and animals linked infection with changes in brain chemistry.
According to Time
, Czech scientist, Jaroslav Flegr, had studied T. gondii‘s effect on human personality and mental illness for decades. His findings suggested that infection with the parasite changes psychological response to a variety of situations. NPR
reports that a study of rats found that infection caused them to lose their fear of cats and become attracted to the odor of cat urine. The behavioral change increased the chance that a rat would be eaten by a cat. This allows the parasite to get into the cat's intestine, which is the only place it can reproduce sexually.
Flegr also suggested that infection with the organism contributes to car crashes, suicides, and mental disorders such as schizophrenia. According to Time
, Fleg said: “Toxoplasma might even kill as many people as malaria, or at least a million people a year.”
Stanford neuroscientist Robert Sapolsky, however, said that "the effects on humans are not gigantic. If you want to reduce serious car accidents, and you had to choose between curing people of Toxo infections versus getting people not to drive drunk or while texting, go for the latter in terms of impact.”
Experts say that the result of the new study is important because about a third of the world's population is infected with the parasite that hides in brain and muscle cells, and very often does not produce symptoms.
reports that Dr. Albert Reece, vice president of medical affairs at the University of Maryland, said: “T. gondii infection is a major public health problem around the world, and many people don’t realize they’re infected. Dr Postolache is a leading expert on suicide neuroimmunology. Suicide is a critically important mental health issue. About one million people commit suicide and another 10 million attempt suicide worldwide each year. We hope that this type of research will one day help us find ways to save many lives that now end prematurely in suicide.”
According to The Telegraph
, Postolache's study is the largest so far to document suicide attempts in connection with infection with Toxoplasma parasite. Postolache's research team at the University of Maryland first reported a connection betwen suicide attempt and T. gondii infection in 2009. He carried out the research in collaboration with scientists from Denmark, Germany and Sweden.
According to scientists, T. gondii is found in the intestines of cats and is spread to human beings through the oocytes cats pass out in their feces. When a human being is infected with the parasite through contact with infect cat feces, it spreads to the brain and muscles where it hides in "cysts" from the host's immune system.
Pregnant women, especially, are advised to avoid all contact with cat feces because they can easily pass the infection to their unborn babies. Babies are unable to produce T.gondii antibodies during the first three months of life.
Postolache, however, noted the limitations of the study which includes inability to determine the cause of suicidal behavior. The Inquisitr
reports that according to Postolache, “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. We plan to continue our research into this possible connection.”
The research scientist posed the question: “Is the suicide attempt a direct effect of the parasite on the function of the brain or an exaggerated immune response induced by the parasite affecting the brain? We do not know. In fact, we have not excluded reverse causality as there might be risk factors for suicidal behavior that also make people more susceptible to infection with T. gondii. If we can identify a causal relationship, we may be able to predict those at increased risk for attempting suicide and find ways to intervene and offer treatment.”
He said: “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.”
reports that although the study found a link between suicide rates and Toxoplasma infection, the absolute risk of suicide is still quite small. Over the 30-year long study, fewer than 1,000 of the participants attempted suicide, and only seven women actually killed themselves. According to Jezebel
, Postolache said the result of the study does not warrant people getting rid of their cats.
The study was published in the Archives of General Psychiatry