September 19, 2025, 8:53 am | Read time: 4 minutes
Cats are popular pets—but could they also be a risk factor for mental illnesses? A systematic review with meta-analysis has examined exactly that: the connection between cat ownership in childhood and the later risk of schizophrenia or similar disorders. The results shed new light on an underestimated topic—and call for more research.
Can Cat Ownership Promote Schizophrenia?
The idea that cat ownership could be a risk factor for schizophrenia is not new—it is based on the suspicion that the parasite Toxoplasma gondii plays a role. This single-celled organism lives, among other places, in the intestines of cats and can infect humans through direct contact or contaminated food. In animals, it is known that an infestation with the parasite makes them more daring and less able to assess risks. Toxoplasmosis can be particularly dangerous for pregnant women. Additionally, T. gondii can affect the central nervous system and is suspected of causing psychological changes, especially in individuals with weakened immune systems.
Previous individual studies have yielded mixed results. Some showed a connection between early cat ownership and an increased risk of schizoid behaviors, while others did not. A possible link was also suspected for so-called psychosis-like experiences, such as perceptual disturbances or social anhedonia. The aim of the present study was therefore a comprehensive, systematic evaluation of all available original studies with a statistical overall evaluation (meta-analysis) to enable reliable statements. The existing research on the question should be consolidated and also clarify whether there is a connection between cat ownership and schizophrenia-related disorders or so-called psychosis-like experiences (PLE).
Study Finds Cat Ownership Doubles Risk of Schizophrenia
The study was conducted by John J. McGrath and colleagues from the Queensland Brain Institute (University of Queensland, Australia) in collaboration with the Queensland Centre for Mental Health Research. It was published in the journal “Schizophrenia Bulletin” (Volume 50, Issue 3, 2023).
The researchers conducted a systematic literature search in five scientific databases (Medline, Embase, CINAHL, Web of Science, and gray literature) for the period from 1980 to May 2023. The meta-analysis included only studies that contained data on cat ownership (before the age of 25) and the later occurrence of schizophrenia-like disorders or PLE.
A significant association was found between early cat ownership and an increased risk of schizophrenia-related disorders. Ten studies showed that individuals with cat contact were about twice as likely to have a risk of schizophrenia as those without.
For psychosis-like experiences (PLE), the researchers could not conduct a pooled analysis due to a lack of comparable measurement methods. Individual studies showed mixed results: some found a connection between cat experiences (e.g., cat bites or contact with hunting cats) and increased PLE scores, while others did not. High-quality cohort studies showed no clear connection in the adjusted analyses.
Did the Cats Really Have Toxoplasmosis?
The results support the hypothesis that contact with cats—especially in childhood—could be a possible risk factor for schizophrenia-like disorders. The results of the adjusted meta-analysis are particularly relevant as they consider various confounding factors (e.g., socioeconomic status, other pets, familial risk factors).
Despite the striking associations, the study also advises caution in interpretation. The quality and consistency of the evaluated studies vary. It is also unclear at what age contact with cats might be particularly decisive, possibly between the ages of nine and twelve.
For PLE experiences, the evidence was inconsistent. The connection with potential Toxoplasma gondii infection remains a central issue: serological evidence for T. gondii was collected in some studies, supporting the biological plausibility of the hypothesis. However, it is unclear whether contact with cats is the decisive risk factor or merely an indirect indication of other environmental or infection risks.
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Other Potential Pathogens in Focus
Even though T. gondii is at the center, scientists are considering alternative explanations. The bacterium Pasteurella multocida, found in the oral flora of cats, is also coming into focus, as it could also have psychological effects.
However, the researchers emphasize that cat owners should not panic. The majority will never develop schizoid personality patterns. Rather, further research is now necessary, particularly large-scale, representative studies that examine how environmental factors and pathogens may be related to mental illnesses. 1, 2
Recommendations for Cat Owners
Despite the inconclusive state of research so far, cat owners can be advised to take the following precautions in everyday life:
- Regularly clean litter boxes (with gloves)
- Wash your hands thoroughly after contact with cats
- Do not feed raw meat
- Attend regular veterinary visits
- Have cats tested for T. gondii infection
The results of this study show how complex the interplay between humans, animals, and the environment truly is—and what role previously overlooked biological factors might play in our mental health.