As if parents of young children didn’t have more than enough things to worry about, here’s another: A few scientists say they think pet cats might increase a kid’s risk of developing schizophrenia.
However, there’s now good news out of this growing field of research, which focuses on the links between a cat-borne parasite that causes toxoplasmosis and mental health disorders. A brand new study of about 5,000 children in Britain found no evidence that cat ownership during gestation or childhood was associated with psychotic experiences that can be early signs of mental illness — such as hallucinations or delusions of being spied on and watched — when they were teenagers.
The new study, which was published in the journal Psychological Medicine, is the latest in a field that’s yielded many alarmist headlines based on various correlations, but not concrete conclusions, about cats making people crazy. And it amounts to a big “not so fast.”
“Many people own cats, which are an important part of the life of many families,” co-author James Kirkbride, a psychiatric epidemiologist at University College London, stated in an email. “Our findings should reassure people that owning a cat in pregnancy or childhood is not related to later risk of psychotic symptoms.”
The cat-toxoplasmosis-psychosis nexus has gotten a lot of attention over the years, but it’s hardly well understood.
It’s clear that the parasite that causes toxoplasmosis infections in people, T. gondii, depends entirely on cats because it reproduces only in cat intestines and is spread through feline feces. And there’s “good evidence,” the study’s authors write, that T. gondii infections are linked to psychosis. So some researchers hypothesize that owning cats in childhood increases the risk of developing mental illnesses, particularly schizophrenia, and a handful of studies in the past have supported this idea. However, people can also become infected with T. gondii from undercooked meat or contaminated water.
The brand new study is much larger than previous ones, and it’s based on data which was collected from children born in the early 1990s and tracked for decades as part of a longitudinal birth cohort study in the area of Bristol, England. That meant the authors could feel certain whether a child grew up with a cat, whereas past research depended much on adults recalling whether they had cats as kids — a method which “can often lead to results that are biased,” said co-author Francesca Solmi, also an epidemiologist.
What the new research doesn’t answer is whether cat ownership during pregnancy and childhood is somehow linked to later schizophrenia, because the participants haven’t yet reached the age of onset of that disorder, which typically develops between ages 18 and 25. However, Solmi added, that if there’s a cat-mental illness connection, the first signs would be detectable when the participants were screened for psychotic experiences at ages 13 and 18.
E. Fuller Torrey, who is a psychiatrist and prominent researcher on the links between T. gondii and mental illness, cited that as one weakness of the study.
“The measuring of unusual experiences and beliefs at age 13 is somewhat controversial. I’ve raised two children, and both had unusual thinking at age 13,” stated Torrey, who was one of the paper’s reviewers. “I think this will become much more important when they’re measuring who developed schizophrenia out of this database.”
Torrey also went on to note that living with a kitty is not the only way cats might pass T. gondii to children.
“Even if we are suggesting that you get it at, say, age 4 when you’re playing in a sandbox, you don’t have to own a cat to have a cat go to the bathroom in it. The cat next door will go to the bathroom in it,” Torrey stated, adding that he doesn’t think families with children should own cats. “I am not reassured by their findings that there’s no relationship.”
However, Solmi went on to say, the findings indicate that owning a cat doesn’t amount to an additional risk for developing psychotic symptoms — in other words, if we assume T. gondii is a driver of mental health disorders, then having a cat around doesn’t seem to be more dangerous than other sources of infection, such as dirty vegetables. (Pregnant women, they specified, should continue to avoid the litter box, because T. gondii infections can cause serious birth defects and complications.)
At the very end of the study, the authors appended an unusual conflict-of-interest statement: They all own or have owned cats, but that did not affect their work, it stated.