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Common Parasite May Increase Suicide Risk

(Image credit: Boumenjapet | Dreamstime)

Women infected with a common parasite called toxoplasma gondii may be more likely to attempt suicide, a new study suggests.

Researchers looked at the health records of more than 45,000 Danish women and concluded that over a 14-year period, women with toxoplasmosis, as infections with the parasite are called, were 53 percent more likely to attempt suicide than their uninfected counterparts. The likelihood of making a suicide attempt increased with the levels of parasite-fighting antibodies, suggesting that the stronger the infection, the larger the risk, the researchers said.

The link between the parasite and suicide attempts held when the researchers took into account other factors that may have affected the results, such as the women's mental health and socioeconomic class.

The study showed an association, but does not prove that toxoplasmosis infections might cause women to attempt suicide, the researchers said.

But if a causal relationship was found, researchers might be able to predict who is at an increased risk for attempting suicide, and find ways to intervene, study author Dr. Teodor Postolache, an associate professor of psychiatry at the University of Maryland School of Medicine.

Further research on the topic could lead to a new vaccination against the parasite, avenues for treating people with toxoplasmosis, or increased efforts to teach people how to reduce transmission, Postolache told MyHealthNewsDaily.

A common infection

Toxoplasma parasites affect a third of people worldwide, and healthy people may develop no symptoms. The parasite is spread through undercooked meat, unwashed vegetables or contact with fecal matter from cats, as the feline family is the only animal host that allows the parasite to reproduce.

The parasite attacks the brain and muscles, but a strong immune system keeps it in check. Infections are more concerning when they happen to people with weakened immune systems, such as pregnant women, people undergoing cancer treatments, and people with HIV.

In the new study, the researchers looked at the records of the Danish women, all of whom gave birth between 1992 and 1995. The infants’ blood was sampled for antibodies against toxoplasma, which indicates an infection in the mother, because babies can't develop their own antibodies until they are 3 months old.

The researchers found that not only was toxoplasmosis infection linked with an increased risk of attempting suicide, but also that womenwith toxoplasmosis were more 81 percent likely to attempt to commit suicide violently, with a gun, sharp object or by jumping. In total, 488 women in the study attempted suicide, 78 violently.

One possible explanation for the link to the increased violence could be an increased level of aggression that comes with infection, Postolache said. In order to attempt suicide, one must "be ready to die and have a capability to kill," he said.

Additionally, the researchers found that women with toxoplasmosis were 25 percent more likely to attempt suicide than women who had previously experienced mental health problems.

A parasite that affects the brain

The new findings are in line with past research suggesting links between toxoplasmosis and schizophrenia and brain cancer, the researchers said.

While the idea of screening people for the parasite may have been "scoffed at 10 years ago," today, the parasite has been shown to be associated with such a wide array of health conditions, and screening is so inexpensive that this may become a viable option, said Kevin Lafferty, a parasite researcher with the U.S. Geological Survey who was not involved in the study.

Lafferty said the link between the parasite and suicide may stem from the parasite's effect on the brain. The infection may make the brain more vulnerable to mental illness and predispose people to suicide. (It's less likely that people with existing mental illnesses are more likely than others to contract the infection, he said.)

"The chemistry of the brain is the underlying common thread here," Lafferty said.

 The research was published today (July 2) in the journal Archives of General Psychiatry.

Pass it on: Women carrying the parasite toxoplasma may be more likely to attempt suicide.

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