Owning cat may double schizophrenia risk Researchers find

According to a recent analysis published on Science Alert, owning a cat may significantly increase an individual's risk of developing schizophrenia-related disorders.

Researchers from Australia conducted a comprehensive analysis of 17 studies published over the past 44 years across 11 countries, including the US and the UK. The study, led by psychiatrist John McGrath from the Queensland Centre for Mental Health Research, found a correlation between cat ownership and heightened odds of schizophrenia-related disorders.

This theory was initially proposed in a 1995 study, which suggested that exposure to the parasite Toxoplasma gondii might be a contributing factor. However, previous research on this topic has yielded mixed results. Some studies suggest that exposure to cats in childhood could increase the likelihood of developing schizophrenia, while others have failed to establish a connection. Additionally, certain studies indicate that cat exposure correlates with higher scores on assessments measuring traits related to schizophrenia, as well as psychotic-like experiences; yet, not all research supports this link.

To clarify these findings, McGrath and his team emphasize the need for a thorough review of existing research on the subject. T. gondii is primarily a harmless parasite that can be transmitted through undercooked meat or contaminated water, but it can also be spread through bites or feces from infected cats. It's estimated that around 40 million people in the US may carry this parasite, often without symptoms. Once inside the body, T. gondii can affect the central nervous system and alter neurotransmitter function. While the parasite has been associated with changes in personality and the onset of psychotic symptoms, including schizophrenia, establishing a causal link remains complex. 

The analysis concluded that there is a "significant positive association between broadly defined cat ownership and an increased risk of schizophrenia-related disorders." "After accounting for various factors, we found that individuals exposed to cats were nearly twice as likely to develop schizophrenia," the research team noted. It's important to consider that 15 out of the 17 studies analyzed were case-control studies, which cannot establish direct cause-and-effect relationships and may overlook variables that influence both exposure and outcomes. 

The authors also pointed out that several of these studies had low quality. While the findings varied across different studies, those deemed higher quality suggested that associations found in unadjusted models might have been influenced by confounding factors. One study indicated no significant link between cat ownership before age 13 and later schizophrenia; however, a significant association was found when focusing specifically on cat ownership from ages 9 to 12. 

This inconsistency highlights that the critical timeframe for cat exposure remains unclear. A US study involving 354 psychology students found no correlation between cat ownership and schizotypy scores. Nevertheless, participants who had been bitten by a cat exhibited higher scores than those who had not. Another study, which included individuals with and without mental health disorders, identified a relationship between cat bites and elevated scores on tests measuring certain psychological experiences, but suggested that other pathogens, like Pasteurella multocida, could be responsible. The researchers concur that more comprehensive and high-quality studies are needed before drawing definitive conclusions. 

"In summary, our review supports a connection between cat ownership and schizophrenia-related disorders," the authors stated. "There is a pressing need for more rigorous studies, utilizing large, representative samples to better assess cat ownership as a potential risk factor for mental health issues."

By Naila Huseynova