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Brain Parasite Linked to Suicide Attempts

Inflammation may cause changes in brain chemistry (Aug. 16)

Researchers at Michigan State University (MSU) reported on August 16 that a parasite thought to be harmless and found in many people may actually cause subtle changes in the brain, leading to suicide attempts.

New research appearing in the August issue of the Journal of Clinical Psychiatry adds to the growing work linking an infection caused by the Toxoplasma gondii parasite to suicide attempts.

About 10% to 20% of the U.S. population has T. gondii in their bodies, but in most people it was thought to lie dormant, said Dr. Lena Brundin, an associate professor of experimental psychiatry in MSU’s College of Human Medicine. In fact, it appears the parasite can cause inflammation over time, which produces harmful metabolites that can damage brain cells.

The work by Dr. Brundin and her colleagues is the first to measure scores on a suicide assessment scale from people infected with the parasite, some of whom had attempted suicide.Those infected with T. gondii scored significantly higher on the scale, indicating a more severe disease and a greater risk for future suicide attempts.

Dr. Brundin stresses, however, that the majority of people with the infection will not 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 ingesting 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.

Dr. Brundin has been looking at the link between depression and inflammation in the brain for a decade. Typically, selective serotonin reuptake inhibitors (SSRIs) have been the preferred treatment for depression. SSRIs are believed to increase the level of the neurotransmitter serotonin but are effective in only about half of depressed patients.

Dr. Brundin’s research indicates that 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.

For more information, visit the MCU Web site.

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