Writing last week for Scientific American, Yale School of Medicine research fellow Jack Turban waded into the controversy surrounding cat ownership, Toxoplasma gondii, and the parasite’s alleged role in mental illness—asking (and answering) the question, “are cats really to blame for psychotic behavior?” As it turns out, not so much.*
“In the largest and best-controlled study to date, the researchers showed that those exposed to cats were at no increased risk of psychosis after controlling for a number of other variables (including ethnicity, social class, and dog ownership—to control for exposure to animal stool).”
But wait—what about all those scary headlines…?
As the study’s lead author Francesca Solmi explains, “previous reports of positive associations between cat ownership and schizophrenia” might be attributable to “small sample sizes and lack of control for confounders inherent to some studies.”
“Earlier studies also relied on retrospective recall, and hence the potential of recall bias, of cat exposure and did not distinguish between ownership in infancy v. later childhood, making it impossible to attribute risk to specific periods of cat ownership over the early life-course.” 
All of which ought to come as welcome news to the American Bird Conservancy, given that organization’s very public “concern” for “the likelihood of infection with Toxoplasma gondii.” And The Wildlife Society, whose recommendation (PDF) for the “removal of free-ranging cats and elimination of feral cat colonies” rests in part on the parasite’s potential for “significant effects on the health of humans.”
And let’s not forget about Peter Marra, who considers toxoplasmosis “perhaps one of the most significant” of all zoonotic diseases—sufficient to warrant unprecedented action from the Centers for Disease Control and Prevention.
“Advertising campaigns underwritten by various government entities have helped discourage smoking. Perhaps billboards warning of the potential maladies brought on by cats carrying Toxoplasma gondii could similarly impact public behavior. As free-ranging cats become recognized as a serious threat to public health—and thus become viewed as a public-health issue—there is hope that more resources can be devoted to managing the problem.” 
Or, you know, maybe not.
*Unfortunately, readers have to drill down five paragraphs before they find the answer to the question posed by the article’s headline, “Are Cats Responsible for ‘Cat Ladies’?” (“your cat friends are just fine”). It’s disappointing to see Scientific American resort to the sort of click-bait move Ryan Holiday describes in Trust Me, I’m Lying: Confessions of a Media Manipulator. (“When you take away the question mark, it usually turns their headline into a lie… After the reader clicks, they soon discover that the answer to the ‘question’ in their headline is obviously, No, of course not.”)
- Solmi, F., Hayes, J. F., Lewis, G. & Kirkbride, J. B. Curiosity killed the cat: no evidence of an association between cat ownership and psychotic symptoms at ages 13 and 18 years in a UK general population cohort. Psychological Medicine. 1–9 (2017).
- Marra, P. P. & Santella, C. Cat Wars: The Devastating Consequences of a Cuddly Killer. (Princeton University Press, 2016).