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‘Harmless’ Parasite May Trigger Suicide Attempts

'Harmless' Parasite May Trigger Suicide AttemptsA parasite thought to be harmless and found in many people may actually cause subtle changes in the brain, leading to suicide attempts, according to new research.

In a new study, scientists were able to link an infection caused by the Toxoplasma gondii (T. gondii) parasite to suicide attempts.

About 10 to 20 percent of people in the United States have T. gondii in their bodies, but in most it is thought to lie dormant, said Lena Brundin, M.D., one of the lead researchers on the study and associate professor of experimental psychiatry at Michigan State University.

But in some people, it appears the parasite can cause inflammation, which produces harmful metabolites that can damage brain cells, she said.

“Previous research has found signs of inflammation in the brains of suicide victims and people battling depression, and there also are previous reports linking Toxoplasma gondii to suicide attempts,” she said.

“In our study we found that if you are positive for the parasite, you are seven times more likely to attempt suicide.”

T. gondii is a parasite found in cells that reproduces in its primary host, any member of the cat family.

It is transmitted to humans primarily through water and food contaminated with the eggs of the parasite, or, since the parasite can be present in other mammals as well, through consuming undercooked raw meat or food.

Brundin has been looking at the link between depression and inflammation in the brain for a decade, beginning with work she did on Parkinson’s disease. Typically, a class of antidepressants called selective serotonin re-uptake inhibitors, or SSRIs, have been the preferred treatment for depression. SSRIs are believed to increase serotonin levels but are effective in only about half of depressed patients, said Brundin.

She noted her research indicates a reduction in the brain’s serotonin might be a symptom, rather than the root cause, of depression.

Inflammation, possibly from an infection or a parasite, likely causes changes in the brain’s chemistry, leading to depression and, in some cases, thoughts of suicide, she said.

“I think it’s very positive that we are finding biological changes in suicidal patients,” she said. “It means we can develop new treatments to prevent suicides, and patients can feel hope that maybe we can help them. It’s a great opportunity to develop new treatments tailored at specific biological mechanisms.”

Source: Michigan State University

‘Harmless’ Parasite May Trigger Suicide Attempts

Janice Wood

Janice Wood is a long-time writer and editor who began working at a daily newspaper before graduating from college. She has worked at a variety of newspapers, magazines and websites, covering everything from aviation to finance to healthcare.

APA Reference
Wood, J. (2018). ‘Harmless’ Parasite May Trigger Suicide Attempts. Psych Central. Retrieved on December 5, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 17 Aug 2012)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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