The Links Between Parasites and the Rage Disorder

Authored by Ailish Delaney

Have you ever heard of intermittent explosive disorder?  Until recently, I hadn’t either. But if studies are to be believed, then the chances are you know someone who has it.

We’ve all seen them – those people who ‘blow up’ at the slightest provocation. The drivers who literally lose their head because a car overtook them. Or the work colleague who explodes with rage at a real (or imagined) slight by a co-worker.

On a day to day basis these people are rational, level headed human beings, but the people around them – friends, family, and co-workers – have all learned to walk on eggshells around them because they know that the slightest provocation can tip the scales and turn them into a rageaholic.

Does any of this ring a bell? It certainly does with me – I can think of several people in my life (mostly past, because let’s be honest, turbulent relationships aren’t easy) who wear this label well.

But it might not be their fault.

cate and angerSure, there are people who are just wired that way, people who like to bully others, shout their way out of a situation and beat their chests to show their alpha male (or female) status.

But others may well be suffering from a latent parasitic infection of the brain, known as toxoplasmosis.

This infection is usually caused by contact with infected cat faeces – failure to wash the hands after emptying a soiled litter tray for instance.

It can also be transmitted through contaminated soil, and undercooked meat.

This parasite (Toxoplasma Gondii), usually goes unnoticed as it rarely causes sickness in people infected by it. But what it does do is cause cysts to develop on the brain, which can remain there for the rest of a person’s life.

Here comes the science bit

According to Emil Coccaro, of the University of Chicago’s Psychiatry Department, the parasite could be responsible for altering the neurotransmitters in the brain, either by overstimulating the part the brain which controls our response to threats, or by dulling the part of the brain which prevents aggressive behaviour.


Emil Coccaro also says that although studies show a direct correlation between Toxoplasma Gondii and aggression, it is not necessarily what causes this behaviour.

He says that it could be that aggressive people are less likely to wash their hands after handling a cat’s litter tray for instance, or are more likely to eat undercooked meat.

This would make sense, I suppose, in that aggressive people tend to have little patience – cooking meat fully requires time, and an impatient, aggressive person might not have the capacity to wait it out, but will eat the meat without it being cooked properly.

The same could be said for emptying a litter tray – it’s easy to just empty it and go, rather than washing hands thoroughly to eliminate any trace of the soiled litter.

I personally have seen a cat owner do exactly that. He became irrationally annoyed at the cat soiling the litter tray (isn’t that what it’s for?) and snatched the tray up, emptied the contents into the bin, refilled it and pretty much threw it down again.

He then carried on eating his sandwich. All without washing his hands.

The poor cat had only done what nature intended, but incurred the completely unwarranted wrath of its owner.

Approximately 30 percent of the human population carries the parasite in their brain, with most of them not knowing anything about their uninvited guests.

According to a study in the Journal of Clinical Psychiatry, sufferers of Intermittent Explosive Disorder are twice as likely to be carriers of the parasite.  358 people were recruited for the study – one third were sufferers of Intermittent Explosive Disorder, one third had been diagnosed with a psychiatric disorder other than IED, and the last third had no behavioural disorders or notable diagnoses.

The results made for interesting reading. Of those with IED, 22 percent were infected with the parasite, compared to 16 percent of those with another psychiatric disorder. Overall, those with any kind of aggression disorder scored significantly higher than the non-aggressive participants.

Ulterior Motive?
Are these parasites cleverer than we give them credit for? It seems that, when rats are infected with the parasite, they becomes more attracted to cat’s urine – they become unafraid of the thing most likely to kill them. As the parasite spends most of its life inside a cat, is this somehow the parasite’s way of completing the circle? A way of getting back to the environment it needs to reproduce?

And if so, what does that mean in the bigger picture, when human brains are infected? What is the parasite’s end goal? That is food for thought, certainly.

The effect on women

While Toxoplasma Gondii can infect both sexes, the effects on women are thought to be much more detrimental.

Two separate studies suggested that mothers who were infected with the parasite were at an elevated risk of self-harm and violent suicide attempts. Although there is still a lot of research to be done, it was thought that maybe the area of the brain that the parasites inhabited was relevant to the effects on behaviour. In the case of self-harm and suicide, was the area of the brain involved that which is responsible for emotional response?

So what can be done?

Sadly, at the moment, there is no known way to rid the brain of Toxoplasma Gondii. The problem is, once it has made its home into the central nervous system, there is no way to reach it without killing the host.

Drugs can be used to manage the infection if it is caught early enough, but as most people don’t even know they are infected, the chances of that happening are slim.

The aggression and rage can sometimes be managed, or at least curtailed somewhat, by counselling and therapy, but until there is an advancement in medicine which can reach the parasites in situ, prevention is the only cure.

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