Your Cat’s Parasite Won’t Make You Psychotic, Study Says

A handful of previous studies offered quite a literal take on the idea of a "crazy cat lady." Some researchers have suggested that felines put their owners at greater risk to developing psychotic symptoms because they commonly carry Toxoplasma gondii, a parasite that's been linked with schizophrenia and hallucinations.

A team of epidemiologists from the University College London set out to test that theory by analyzing data from the Avon Longitudinal Study of Parents and Children (ALSPAC), which followed children born in 1991 and 1992 until they were 18 years old. For this study, researchers specifically focused on participants with complete data on psychotic experiences in early adolescence, when they were 13 years old (6,705 in total) and in late adolescence at age 18 (4,676 in total). From questionnaires filled out by participants' mothers, researchers gathered information about the children's exposure to cats during pregnancy, at 47 months old and at 10 years old—"since T. gondii infection is proposed to increase psychosis risk by affecting early life neurodevelopment," the study notes. They also took into account other variables, such as maternal marital status in pregnancy and the number of moves the child endured before turning four.

Ultimately, the study found that there was no evidence that cat ownership during pregnancy or while growing up was linked with the onset of psychotic symptoms later in life. While "cat ownership in pregnancy was associated with higher odds of [psychotic experiences] at age 13 years in all models, as was cat ownership at age 4 years," the study's authors note, once they factored in other variables, the cats were off the hook.

There were a number of reasons why their results differed from past studies, the authors note. "Our study was based on [psychotic experiences] in early and late adolescence, unlike other studies which were based on a clinical diagnosis of schizophrenia," they write. Previous work also had smaller sample sizes and didn't consider other possible explanations.

Because of those methodological limitations, the current study's results weren't that surprising, says Francesca Solmin, a psychiatric epidemiologist and lead author on the study.

Solmin says that she and her team became interested in investigating the link between cat ownership and psychosis partly because most of the authors on the work actually have a furball of their own. "We were naturally curious about the poor quality of science until now on the link between cat ownership and psychotic outcomes," she tells Broadly. "One day we were talking about this in our research group, and we said, 'Wouldn't it be great if we had better data on this?' At that moment we realized we did—and we used the data to answer that question."

The biggest takeaway of this new research is for the average person, Solmin says. It's "reassuring, considering that many people own and care for their cats."

But, she adds, "there is some evidence that maternal infection with T-Gondii is associated with a child's long-term risk of having psychotic disorders like schizophrenia. Future research should therefore focus on better understanding the mechanisms by which these types of infection might lead to mental illness, and many researchers are currently investigating this."

Interestingly, this isn't the only recent study to shed light on the potential effects of cat ownership: Another study that came out last year in the Journal of Evolutionary Psychology found that individuals infected with toxoplasmosis, caused by the cat parasite Toxoplasma gondii, "expressed higher attraction to bondage, violence, zoophilia, fetishism, and, in men, also to masochism."