More than 80 studies, including those led by Dr. Torrey and co-investigator and Johns Hopkins University neurovirologist Dr. Robert Yolken, detail links between Toxoplasma gondii and schizophrenia, including four studies reporting "that individuals with schizophrenia, compared to controls, have had more contact with cats during childhood." A 2015 study at the Academic Medical Center in Amsterdam reported by CBS News found that "an individual infected with T. gondii was almost twice as likely to develop schizophrenia."
Scientists are quick to caution against jumping to conclusions that these scientific studies yield definitive evidence of the crazy cat lady theory in action. "Well, first of all, we haven't proven anything," says Dr. Torrey. "What we've shown is that there are certain aspects of Toxoplasma gondii that would be consistent with some of the symptoms of schizophrenia, but none of us would say that we've shown Toxoplasma gondii causes schizophrenia, or Toxoplasma gondii causes crazy cat ladies, etc."
Schizophrenia is a serious and chronic mental illness, affecting 1% of the general population. "Crazy" is an insensitive word for describing individuals afflicted with mental illness. No matter the probability of a parasite found in cat poop leading to schizophrenia, the label "crazy" can and should be scrubbed from the lexicon surrounding Toxoplasma gondii.
But what about the "crazy cat lady" stereotype?
Women are not at greater risk for infection by Toxoplasma gondii, by the way. While Flegr maintains that the parasite yields different behavioral manifestations for men versus women, there's no data indicating that one sex is more likely than the other to contract the infection. On top of that, Flegr's observed personality distinctions contradict much of the classic "crazy cat lady" personality type that such women are antisocial recluses. As reported in The Atlantic's 2012 profile of Flegr, "[...] males who had the parasite were more introverted, suspicious, oblivious to other people's opinions of them, and inclined to disregard rules. Infected women, on the other hand, presented in exactly the opposite way: they were more outgoing, trusting, image-conscious, and rule-abiding than uninfected women."
Not only is the stereotype both inaccurate and offensive; it also diminishes the seriousness of the disease theorized to explain it.
"It's a very significant source of damage to people in a way that matters," says Dr. McLeod of toxoplasmosis. "There's a lot of hype about things it might do, but we know the things that it can do. [An infected] baby can end up without sight, without cognition, all the things that Zika can do, this virus can do, and it's here with us right now."
And despite the fact that the parasite is specific to cat feces, the indoor house cat is, more than likely, not at fault, says the Cornell Feline Health Center at Cornell University's College of Veterinary Medicine. Feral cats and outdoor cats are the more probable culprits; even still, you can get toxoplasmosis whether you interact with cats regularly or not.
"It's a very common parasite, it's in the environment," says Dr. McLeod. "You just have to live in the world to get it."
"Cats can make nice pets," adds Dr. Torrey. "But there are some aspects to what has come out so far that makes some of us uneasy, and would suggest that, especially for children, you may want to take certain precautions" -- such as covering sandboxes when not in use. Otherwise, he says, cat companionship is not cause for alarm or panic.
"I think it's important to stress that nobody should go home and shoot their cat or whatever."
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