Cats Might Be the Reason Some People Are So Terrible

By Susan Rinkunas
03.24.2016

Sassy cat. Photo: Vladimir Godnik/Getty Images

Cat haters are gonna love this one: A new study found that carrying the toxoplasma gondii (t. gondii) parasite — which is best-known for being transmitted through the feces of infected cats — is associated with increased aggression and intermittent explosive disorder (IED), a psychiatric condition characterized by recurrent, very angry outbursts like road rage. It affects as many as 16 million people.

Toxoplasmosis infection is very common — about 30 percent of the population has it — but the authors note that it doesn’t cause aggression problems in everyone. In fact, it’s usually asymptomatic and harmless in otherwise healthy people. You can get it from undercooked meat or contaminated water and soil, but many people know it as a litter-box parasite.

For a study published in Journal of Clinical Psychiatry, researchers at the University of Chicago looked at blood samples from 358 adults and then looked at how they scored on traits like aggression, anger, and impulsivity. About a third of them had IED, another third had some other psychiatric disorder, and the last group included people with no psychiatric history.

They found that people with IED were more than twice as likely to have toxoplasmosis compared to the healthy control group (22 percent versus 9 percent). About 16 percent of people with a non-IED psychiatric disorder had the infection, but their aggression and impulsivity scores were similar to the control group. IED subjects had higher scores in both measures and, overall, people with toxoplasmosis ranked higher in aggression than those without it.

Before you freak out, researchers aren't saying you should put your fur ball up for adoption. As the co-author said in a release, "Correlation is not causation, and this is definitely not a sign that people should get rid of their cats." Though they believe that the parasite takes up residence in the brain in some people, they don’t quite understand how this all works. It’s even possible that aggressive people are more likely to have more cats or eat more undercooked meat than chiller humans.

Cats have a bad rap when it comes to toxoplasmosis because they're the only host in which the parasite can reproduce sexually, but the good news is that indoor cats seem unlikely to get infected in the first place. The Centers for Disease Control and Prevention says that cats get the bug after eating rodents, birds, or raw meat from other animals that are infected.

If you have an outdoor cat and you're pregnant or have a weakened immune system, you should probably try to get out of litter-box duty, the CDC says, but if you can't, disposable gloves and a good hand-washing will keep you safe.

Thus ends your guide to defending a much-maligned cat problem to dog people.


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