It Is Time to Stop Denigrating the Domestic Cat with Spurious Links between Toxoplasmosis and Human Mental Health

It has happened before (e.g a link with schizophrenia which fizzled out). Now we have an article in the online newspapers about a so-called “link” between toxoplasmosis and a human psychiatric condition known as intermittent explosive disorder (IED).

I would like to comment on this in defence of the cat. Firstly, it is important to state that one of the co-authors of the study carried out at the University of Chicago said:

“Correlation is not causation and this is not a sign that people to get rid of their cats. We don’t yet understand the mechanisms involved. It could be an increased inflammatory response, direct brain modulation by the parasite, or even reverse causation where aggressive individuals tend to have more cats or eat more undercooked meat. Our study signals the need for more research and more evidence in humans.”

If you want to summarise that it would be this: cats cannot be said to be the cause of anger in humans such as road rage which has been referred to in the Times newspaper. They say that “road rage and other acts involving a sudden loss of self-control could be linked to a parasite spread by cats”.

The Times author goes on to say that, “Toxoplasma gondii doubles the chances of suffering bouts of uncontrollable anger, a study found…”. This is misleading when referring to the researcher’s quote above.

The first point I’d like to make is that the so-called psychiatric condition described as IED is a human construct by which I mean somebody at some stage, probably a medically qualified scientist, coined the phrase “Intermittent Explosive Disorder”. Before that it would have been described as a person who became unjustifiably angry and out of proportion to the cause of the anger.

There are many reasons why people become angry, the most likely of which is that they are frustrated, irritable or under stress and pressure. They may be in a psychological corner and trapped. They may be depressed; all of which are compounding factors. Also, I would challenge the human construct of IED. I’m sure that somebody has challenged it before. It could be argued that it does not exist. There are other examples of debatable “human created illnesses” such as ADHD in children.

Secondly, studies such as this one can be highly misleading and they are often picked up by reporters of online newspapers who emphasise certain aspects of the study to dramatise their article at the expense of the domestic cat. This is unethical, quite obviously.

The study in question, led by Emil Coccaro of the University of Chicago, involved the participation of the 358 US adults. Twenty-two percent of participants diagnosed with IED also tested positive for Toxoplasma gondii. In non-infected individuals only 9% had the condition. That is the supposed link; hardly convincing.

The lead researcher reinforces the fact that they do not know whether there is a causal link. He said:

“We do not know if this relationship is causal, and not everyone that tests positive for toxoplasmosis will have aggressive issues.”

IED has been linked to psychiatric conditions including schizophrenia, bipolar disorder and suicidal behaviour. It is believed that IED affects up to 16 million Americans.

Toxoplasma gondii is a parasite which is found in cat faeces and contaminated food. Many people carry the parasite without realising it. Some people suggest that up to a third of UK citizens will be infected at some point in their lives. Click on this link for the truth about toxoplasmosis.

All right, I have provided a bit of background information about this parasite but the important issue that I wish to raise is that there journalists and newspaper reporters must take a more responsible attitude especially with respect to their headlines. They write headlines which are highly provocative. Then somewhere in the article they may refer to information and facts which tell a different story but this information is often not read because readers of online newspapers tend to skim the articles and read the first dozen lines and then move onto the next article.