Owning a cat may double schizophrenia risk, study finds

A major review of decades of research found that people exposed to cats had roughly twice the odds of developing schizophrenia-related disorders compared to those who weren't. Before you start side-eyeing their furry roommates, note that the study found an association, not proof that cats cause schizophrenia. Let’s look further into the study.

What the researchers found

The research comes from a 2023 review led by scientists at the Queensland Centre for Mental Health Research in Australia. The team analyzed 17 studies conducted across 11 countries over the past four decades, looking for possible links between cat ownership and schizophrenia-related conditions.

After reviewing the data, the researchers found a significant association between cat exposure and an increased likelihood of schizophrenia-related disorders.

According to the authors, people exposed to cats had approximately twice the odds of developing these conditions. That sounds dramatic, but it's important to understand what the study does and doesn't show.

Why cats entered the conversation in the first place

The theory is not actually about cats themselves. It's about a parasite called Toxoplasma gondii, often shortened to T. gondii. Cats can carry the parasite and spread it through infected feces. Humans can also pick it up from undercooked meat or contaminated water.

The parasite is surprisingly common, as the Centers for Disease Control and Prevention estimate that more than 40 million people in the U.S. carry it, often without showing any symptoms. 

Researchers have long been interested in T. gondii because it can persist in the nervous system and may influence brain chemistry. Some studies have linked the parasite to personality changes, psychotic symptoms, and certain neurological conditions. The keyword here is linked, as scientists still don't know whether the parasite directly causes these effects.

The evidence is far from settled

Not every study found the same result. Some research suggested childhood exposure to cats was associated with a higher risk of schizophrenia-related traits later in life. Other studies found no meaningful connection at all.

One study reviewed by the researchers found no association between cat ownership before age 13 and schizophrenia. However, it did find a connection when focusing on a narrower age range between 9 and 12 years old.

Another study involving psychology students found no relationship between cat ownership and schizophrenia-related traits, although people who had been bitten by cats scored higher on certain psychological measures. In short, the findings are all over the place.

Should cat owners be worried?

The researchers themselves caution against jumping to conclusions. Most of the studies included in the review were case-control studies, which are useful for spotting patterns but cannot prove cause and effect. There are also many other factors that could influence the results, including genetics, environment, family history, health conditions, and socioeconomic factors.

The authors also noted that several of the studies they reviewed were considered low quality.

That means the apparent connection could weaken or disappear entirely as better research becomes available. So, you do not have to get rid of your cat over this information. Keep in mind that scientists are still trying to understand the many factors that contribute to complex brain disorders and that process is rarely as simple as a headline makes it sound.

Source: ScienceAlert