Sunday 17 December 2023

"Link" between cat ownership and schizophrenia DOES NOT PROVE CAUSE AND EFFECT

As usual, from time to time the news media like to claim that owning a cat can cause schizophrenia. They cite studies and a new one has recently been published. But the news media reporters tend or always miss a very important point which I'll explain.

In broad terms you can categorise scientific studies into two groups: those that are observational and those that prove cause and effect.

Observational studies

These simply observe what is going on and report on it. So in the study referred to (see citation at base of this post) they found the following: "Our findings support an association between cat exposure and an increased risk of broadly defined schizophrenia-related disorders" and this: "We found that individuals exposed to cats had approximately twice the odds of developing schizophrenia". But this does not prove that owning a cat increases the chances of the owner developing schizophrenia.

It might but it is not proved scientifically through a detailed scientific analysis of the transference of the zoonotic disease T. Gondii from the cat to the person. The argument is that T. Gondii causes schizophrenia. But the observed cat owners might be predisposed to schizophrenia for any number of reasons and they just happen to own a cat.

Or the results might be explained by the fact that people who have fragile minds are more likely to adopt a cat for support and company as they find it harder to find a partner who accepts them. That last point is probably the most likely reason for this link between exposure to cats and schizophrenia-related disorders.

Cause and effect

I have touched on this above. The study would have to prove through hard science that cats caused these illnesses and as far as I know they have not. The study in question reviewed 17 early studies over 44 years.

I have done a lot of work on this topic and I have never seen it proved that cats cause schizophrenia-related illnesses.

One last point: often scientists have an axe to grind. They might dislike cats. Or they are funded by businesses who dislike cats. Or governments who have an agenda such as to keep cats inside the home full-time to protect native species or protect native species by reducing the domestic cat population. This kind of study might put people off adopting a cat for instance.

Click the following link to read another article about cat poop causing mental illness: Inconclusive study does not find Toxoplasma gondii infection causes schizophrenia in people.


Beware studies in general. Many are excellent and very useful but some are not. A recent story from the UK reported that one online journal deleted 40,000 studies as they were dubious. It is believed that they were churned out to boost the scientists' CV. They were fake and the journal had not been rigorous enough in vetting them.

RELATED: Beware of "bad science" research papers published online.

The study

John J McGrath, Carmen C W Lim, Sukanta Saha, Cat Ownership and Schizophrenia-Related Disorders and Psychotic-Like Experiences: A Systematic Review and Meta-Analysis, Schizophrenia Bulletin, 2023;, sbad168,

P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.

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