Evidence Tentative for Links Between Cat Parasite and Schizophrenia


The balance of evidence “suggests” some kind of association between T. gondii, a common parasite found in cats, and schizophrenia, bipolar, obsessive-compulsive disorder and addiction, according to a meta-analysis in Acta Psychiatrica Scandinavica. However, the relationship does not seem to be as strong as has been argued by other researchers such as E. Fuller Torrey, the authors wrote.

A team of researchers in The Netherlands reviewed 50 studies looking at the potential association of T. gondii to psychiatric disorders. There did seem to be significant associations especially with schizophrenia, they reported, but there was also significant publication bias, including many unpublished studies.

“After controlling for evidence of publication bias, the association of Toxoplasma gondii infection with schizophrenia seems to be smaller than previously estimated,” the authors wrote. Furthermore, other moderating factors, such as the level of existing infection in a general population, “accounted for 56% of the observed variance in study effects.”

“We hypothesize that there is a limited population at risk, by which T. gondii infection plays a role,” wrote the researchers. They also noted that being diagnosed with, developing, or being treated for schizophrenia seemed to be associated with a recurrence of a latent infection. “These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia reactivation of latent T. gondii infection may occur,” they wrote.

The researchers argued that “uncertainty concerning the support for a causal etiology still remains.”

Sutterland, A. L., G. Fond, A. Kuin, M. W. J. Koeter, R. Lutter, T. van Gool, R. Yolken, A. Szoke, M. Leboyer, and L. de Haan. “Beyond the Association. Toxoplasma Gondii in Schizophrenia, Bipolar Disorder, and Addiction: Systematic Review and Meta-Analysis.” Acta Psychiatrica Scandinavica, April 1, 2015, n/a – n/a. doi:10.1111/acps.12423. (Abstract)


    • Toxoplasmosis and Encephalitis can cause inflammation of the brain. Inflammation of the brain can cause psychosis. We know toxoplasmosis can be dangerous during pregnacy. The toxoplasmosis parasite remains in the brain for life. Therefore , all psychiatrist should test for the toxoplasmosis.
      Furthermore, in my opinion, cat owners are more likely to have had a cat during their childhood. So you could say cats run in families.
      I’m sure there are many different causes of psychosis, however, toxoplasmosis could possibly be one of them.

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  1. How do we know the most common cause of schizophrenia is not psychiatrists misdiagnosing people as “psychotic,” then putting people on neuroleptics. Which are known to cause psychosis / schizophrenia symptoms:

    “neuroleptics … may result in … the anticholinergic intoxication syndrome … Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures.”

    Perhaps almost all schizophrenia is actually misdiagnoses of the central symptoms of neuroleptic induced anticholinergic intoxication syndrome.

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  2. Psychosis has been documented in human populations for thousands of years, long before neuroleptics or any other types of drugs were prescribed. Although it is certainly possible to become psychotic from taking these drugs, there are many other known causes. Bacterial and viral infections certainly can cause psychosis as well.

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    • HIV is the most well known example.

      However, one has to remember that “schizophrenia” is not a valid diagnostic entity – it’s like saying that fever and headache are caused by this or that. There may well be some forms of psychosis that are caused or precipitated by T. gondii but it’s clearly not a causative in the majority of cases.

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  3. Everybody can feel right about something scientifically determined–even when that result is a new question. But these days psychiatry causes the most behaviors and experiences to get called brains diseases compared to any other set of causes. No matter how deservedly the particular phenomena might sometimes be thought pathological, that is the true major factor in having the pathological misidentified or not identified, or the non-pathological labelled and stigmatized. What else is there to get at about this? Most adult persons have experienced psychosis, just not for very long, and mainly after staying up for way too long and working too hard (See Allan Hobson in “Out of its Mind”, although I think he’s not very critical at all of the fields in question….) Everyone has experienced some extremes of emotional distress or seen them before age six, and our exposure to such phenomena never stops during our lifetimes. Or look at the recent report published here on MIA–


    This was a help for suggesting the normalcy inherently retained by implication of equal humanity for anyone “getting way out there”. But whatever the message from studies like this one on a cat parasite, the wrong response is to believe in saying–See how carefully and devotedly psychiatrists work on these real and important problems of human suffering! Let’s help them out!

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  4. Even if the correlation is real there are still many ways that could potentially explain it like existence of common risk factors (like living in neighbourhoods where you’re exposed to stray cats as a child) or lower immune system function associated with prolonged stress. The latter one is very well known to be strongly associated with “schizophrenia”. Btw, in some regions of the world up to 95% of the people are infected – should they not have higher rates of psychosis?

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