Robert H. Yolken, MD
Robert H. Yolken, MD, professor, pediatric infectious disease, The Johns Hopkins University School of Medicine, director, developmental neurovirology, Johns Hopkins Children’s Center, Baltimore.
My friend, a cat owner, kept seeing news reports about “cat ladies” being at higher risk for suicide because of exposure to a certain parasite that’s carried in cat feces.
It sounded wacky, so I investigated.
The parasitic infection is called toxoplasmosis, and more than 60 million men and women in the US have it, according to the CDC.
Owning a cat can increase your risk for this infection because you can get it by handling cat feces, but lots of other stuff can also increase your risk, including eating or handling undercooked meat…accidentally ingesting contaminated soil, such as from not washing your hands after gardening…eating contaminated, unwashed fruits or vegetables…drinking contaminated water…or receiving an infected organ transplant. And pregnant women can pass the infection to their unborn children.
I had to find out how an infection could be linked to a self-inflicted act such as suicide.
The vast majority of infected people have no symptoms. But the parasite can cause brain and vision problems in those with weak immune systems, and it can be dangerous in fetuses—potentially causing mental disability, blindness or even death, which is why pregnant women are routinely advised to let someone else take over litter box duty.
But now two recent studies reveal a link with suicide.
In one study, researchers discovered that infected women were one and a half times as likely to attempt suicide as women who tested negative—even after controlling for mental illness. In another study, researchers discovered that men and women who had attempted suicide were seven times as likely to be infected with the parasite, compared with people who had never attempted suicide.
Remember, the research hasn’t shown a causal relationship between the infection and suicide—only an association.
Why might the infection make you want to attempt suicide? I posed that question to the senior author of both studies, Teodor T. Postolache, MD. Since the infection rarely causes symptoms, it’s unlikely that most people in the study felt so sick from the infection that they wanted to end their lives, he told me. (He can’t say for sure because this was an epidemiological study that analyzed a population retrospectively.) It could be that the infection causes alterations in brain functioning that leads to suicidal behaviors, Dr. Postolache said.
“But it’s also possible that the reverse is true. Some behaviors associated with suicide—such as poor hygiene, including not washing hands after handling raw meat—may make a person more susceptible to infection,” Dr. Postolache said.
In an otherwise healthy person who is not pregnant, treatment is usually not necessary because the immune system generally prevents the infection from causing symptoms. Those who are pregnant and/or have weak immune systems might be given antibiotics or antimalaria drugs to reduce or eliminate symptoms (at least temporarily) and/or to prevent a baby from becoming infected. But which drugs to use and how effective they will be are still being researched.
One problem is that this infection lives inside you forever—so symptoms may flare up and recede, but the infection can never be cured. Another problem is that the drugs listed above have serious potential side effects, including the suppression of bone marrow growth and liver toxicity.
“Unfortunately,” said Dr. Postolache, “even if you know that you’re infected, it’s not always clear whether you should be treated—or how.” But if you’re experiencing cognitive issues, vision problems or suicidal thoughts—especially if you’re pregnant or have a weak immune system—ask your doctor if you should be tested and/or treated.
The best thing to do, said Dr. Postolache, is take precautions to help prevent yourself from getting infected. Follow his tips…
• Be cautious if you own a cat. Keep your cat in the house as much as possible…feed it only canned or dried cat food or well-cooked meat rather than raw meat…and clean the litter box every day (or ask someone else to, if you’re pregnant), because the parasite needs to sit in the litter box for more than a day to become infectious.
• Peel or wash fruits and vegetables. Wash them in hot, soapy water before eating or cooking them. Also, before using them, wash all cutting boards, utensils, dishes and counters with hot, soapy water.
• Thoroughly cook meat. Don’t just “eyeball it”— use a food thermometer when cooking meat and follow the government’s safety recommendations.
• Wear gloves when gardening. And wash your hands with hot, soapy water after working in soil.
Since this article was published, a new study has come to more reassuring conclusions about the role of toxoplasmosis and mental health in humans.”
