Is This Cat Parasite Really Making People Kill Themselves?

The parasite Toxoplasma gondii is already the stuff of whoa crazy! internet lore to a fairly high degree as that thing that you can get from your cat’s crap that might cause schizophrenia, via the disease Toxoplasmosis. Indeed, of you’re reading this site now, there’s a pretty good chance you’ve heard of the fabled cat crazy disease already, either here or elsewhere. And maybe as a result you’ve been a little more conscientious about washing your hands after cleaning the ol’ litter box and/or making sure your cat meat is cooked sufficiently.

Well, here’s some more Toxoplasma gondii news: According to a new study in the Journal of Clinical Psychiatry, researchers at Michigan State University have identified a link between suicide attempts and parasitic infection. So, yes, it would seem that your cat could be causing suicidal thoughts. Sorry.

“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," says Lana Brundin, one of the paper’s authors. "In our study we found that if you are positive for the parasite, you are seven times more likely to attempt suicide." Basically, this conclusion comes as a result of comparing patients testing positive for the parasite — about 10 percent of everyone in the U.S., closer to 20 in Sweden — and patients scoring highly on the Suicide Assessment Scale that had also previously attempted suicide. The researchers took 54 in-patients, the suicide attemptees, at Lund University Hospital in Sweden and 30 people randomly selected from the general Swedish population and tested them for the parasite (and herpes). The resulting statistical model showed a clear correlation.

We still don’t understand a lot about our cat parasite friends, like whether it’s the parasite itself or the body’s reaction to it that causes problems, but we do know that post-infection it tends to hang out in the area of the brain related to impulsivity, where it possibly interferes with the brain’s ability to synthesize the dopamine transmitter. This is quite possibly related to immune reactions to the parasite and related inflammation; past research from Lund University has found links between immune system activity and suicide attempts/suicide.

The cat-brain-parasite is a lot more than a weird-medicine novelty — it points to potential new and crucial treatments for depression and other psychiatric disorders. Mental illnesses tend to be regarded as imbalances in serotonin levels in the brain, and pretty much every depression drug out there acts on serotonin. But drugs work on only about half of depression patients, which is, yes, depressing as hell. But if researchers can get at the core of how and why immune system reactions affect mental health, we’re looking at whole revolutions in treatment.

“I think it's very positive that we are finding biological changes in suicidal patients," Brundin adds. "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."

Also, cat people, wash your damn hands.

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