A new scientific review has raised concerns about a possible link between owning a cat and a higher risk of developing schizophrenia-related conditions. The findings, drawn from four decades of global research, suggest that cat ownership could potentially double a person’s chances of experiencing schizophrenia-related symptoms — but experts say more high-quality studies are urgently needed.
What the New Review Found
A team led by psychiatrist Professor John McGrath at the Queensland Centre for Mental Health Research in Australia reviewed 17 studies from 11 countries, including the UK and the US, published over the past 44 years.
Key Findings
The researchers reported “a significant positive association” between cat ownership (broadly defined) and a higher risk of schizophrenia-related disorders.
The review suggests individuals exposed to cats may have twice the odds of developing schizophrenia.
However, most available studies are not high-quality, and many cannot prove cause and effect.
The authors stressed the need for better-designed research to understand this relationship more clearly.
Why Cats Might Be Linked to Schizophrenia Risk
The idea that cats could be connected to schizophrenia first emerged in 1995, with scientists pointing to a parasite called Toxoplasma gondii (T. gondii).
What Is Toxoplasma Gondii?
A common parasite found in undercooked meat, contaminated water, and cat faeces.
Estimated to infect around 40 million people in the US alone, often without causing symptoms.
Known to reach the central nervous system, possibly influencing neurotransmitters and brain function.
Potential Effects of T. gondii Exposure
Researchers have linked T. gondii infections to:
Subtle personality changes
Psychotic-like symptoms
Certain neurological conditions, including schizophrenia
But experts warn that association does not equal causation. There is still no proof that the parasite directly causes schizophrenia — or that transmission from cats is the main source.
Mixed Results Across Global Studies
While some studies found a link between childhood cat ownership and later schizophrenia, others did not. The review highlights major inconsistencies in the existing research.
Examples of Conflicting Results
One study found no link between owning a cat before age 13 and later schizophrenia — but did find a significant association when focusing on ages 9 to 12.
A US study of 354 psychology students found no connection between cat ownership and schizotypy scores.
However, the same study noted that students who had been bitten by a cat had higher schizotypy scores.
Another study also linked cat bites to unusual psychological experiences but suggested the culprit might be other bacteria, such as Pasteurella multocida.
These inconsistencies suggest that:
The timing of exposure may matter.
Other infections besides T. gondii could play a role.
Many studies suffer from limitations such as small sample sizes or poor-quality methodologies.
Why More Research Is Needed
Most of the studies covered were case-control studies, a type of research that:
Cannot establish cause and effect
Often struggles to adjust for other influencing factors
Is prone to bias
The authors of the review emphasise that:
Many of the higher-quality studies showed weaker associations.
Some results might be explained by confounding factors that weren’t properly accounted for.
What Experts Conclude
Despite the mixed evidence, the review found overall support for an association between cat ownership and schizophrenia-related disorders. But the authors strongly caution against drawing firm conclusions at this stage.
The Researchers’ Final Message
Cat ownership might be a risk-modifying factor for mental health.
The link is not proven, and the quality of existing evidence varies widely.
Larger, better-designed studies using representative samples are essential before any definite claims can be made.
Should Cat Owners Be Worried?
At present, there is no clear evidence that owning a cat directly causes schizophrenia. The findings are only observational and need stronger confirmation.
Experts advise:
Practising good hygiene when handling litter boxes
Cooking meat thoroughly
Taking standard precautions against infections
For now, cats remain beloved companions, and researchers simply call for more scientific clarity on this long-standing question.
Sources
Queensland Centre for Mental Health Research
Review findings published in 2023
Studies from the US, UK, and nine other countries over 44 years
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