New Study Finds No Link Between Childhood Cat Ownership and Psychosis

Cats can be manipulative. There's no doubt about that. But are they controlling our minds with their poop? Probably not. Contrary to prior reports, a new study published in the journal Psychological Medicine found that living with a cat in early life did not increase subjects’ risk of psychotic episodes in adolescence.

The premise behind the original idea is less improbable than it sounds. Cats are the host of choice for Toxoplasma gondii, a parasite that has been shown to cause dramatic behavior changes in rodents. (Mice infected with T. gondii lose their fear of cats and become downright friendly, which leads to them getting eaten, which buys the parasite a ticket into its favorite feline hangout.) A few controversial studies have linked cat ownership with schizophrenia and psychotic episodes, but many researchers remain skeptical.

Psychiatrist Francesca Solmi and her co-authors are among those skeptics. They decided to put the theory to the test, focusing specifically on the effects of cat ownership on two vulnerable populations: kids ages 4 to 10 and developing fetuses.

They tapped into a large-scale survey called the Avon Longitudinal Study of Parents and Children (ALSPAC), which has monitored the health of thousands of British kids since the 1990s. For the current study, the researchers compared the mental health of teenagers who had grown up with cats with that of kids in cat-free homes.

At first, it seemed like the psychosis theory might have been at least a little bit correct: The results did suggest a small link between cat ownership and psychotic symptoms at age 13. But once the team adjusted their analysis to consider other variables like family income and crowded home situations, the link disappeared.

"The message for cat owners is clear: there is no evidence that cats pose a risk to children's mental health," Solmi said in a statement. “Previous studies reporting links between cat ownership and psychosis simply failed to adequately control for other possible explanations."

But even if T. gondii has no hand in mental health issues, that doesn’t mean it’s harmless. “There is good evidence that T. gondii exposure during pregnancy can lead to serious birth defects and other health problems in children,” senior author James Kirkbride said. “As such, we recommend that pregnant women should continue to follow advice not to handle soiled cat litter.”