Testing positive for a common parasite that lives in the bodies of 10 – 20% of Americans is linked to a sevenfold higher risk of attempted suicide according to new research.

This was the main finding of a study appearing in the August issue of The Journal of Clinical Psychiatry that supports growing evidence linking infection by the Toxoplasma gondii parasite to suicide attempts.
A Common Parasite
T. gondii is a common protozoa (parasite) that once ingested travels to the brain, where it can cause subtle changes over time. It reproduces in the cells of its primary host, which is any member of the cat family.

Human sources of infection include any food or water contaminated with eggs from the parasite. Cat litter is another source, hence why it is often referrred to as the “cat litter parasite”. T. gondii can also be picked up from eating undercooked food or raw meat from animals that carry the parasite.
Inflammation in the Brain
Lena Brundin, of Michigan State University, co-led the new study. She told the press that between one in ten and one in five people in the US carry the parasite, and while it was thought to lie dormant, it in fact appears to cause inflammation that produces metabolites that accumulate over time and can harm the brain.

“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,” said Brundin, an associate professor of experimental psychiatry in the College of Human Medicine at MSU.

For example, last month saw the publication of a study that linked higher suicide risk in new mothers to T. gondii.