Got Road Rage? There’s a Good Chance You’ve Been Infected By This Parasite

People suffering from "rage" disorder are twice as likely to have been exposed to T. gondii.

Researchers from the University of Chicago found that toxoplasmosis, a parasitic infection in the brain that is carried in about thirty percent of all humans, is associated with intermittent explosive disorder (IED) and increased aggression.  The parasite that causes toxoplasmosis, Toxoplasma gondii, is typically found in undercooked meats, contaminated water, and within infected cat feces. Toxoplasmosis is typically harmless in healthy adults, however because the parasite normally resides within the brain, previous research has linked it to psychiatric conditions like bipolar disorder and schizophrenia.

^{Toxoplasmosis life cycle. Courtesy of the CDC.}

Now, a new study suggests that people suffering from road rage or other impulsive anger disorders are twice as likely to have been exposed to toxoplasmosis.

The study looked at 358 adult subjects, which were evaluated for IED, personality disorders, depression and other forms of psychiatric disorders. The participants were also rated on their traits, including things like, aggression, anger, and impulsivity.  One third of the participants had IED, and one third were healthy controls with no psychiatric problems. The last third of the participants had some form psychiatric disorder which wasn’t IED.  The last group was used as a control, so that a clear conclusion could distinguish IED from other confounding psychiatric problems.

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Blood test revealed that, within the IED diagnosed group, 22 percent tested positive for toxoplasmosis versus only 9 percent within the healthy group of participants. Roughly 16 percent of the psychiatric control group tested positive for toxoplasmosis, but were ranked with aggression and impulsivity scores similar to those in the healthy control group.  The IED group scored a lot higher on both measures.  

Over the whole study, those participants who were toxoplasmosis positive, scored much higher on scores of anger and aggression.  The findings suggested that toxoplasmosis is strongly correlated with increases in aggression. The researchers cautioned that the results do not necessarily address whether toxoplasmosis causes increased aggression or IED but only suggested a correlation between increased aggression in those participants who tested positive for toxoplasmosis.

The co-author of the study, Royce Lee,MD, stated in a press release, “Correlation is not causation, and this is definitely not a sign that people should get rid of their cats.”

“We don’t 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.”

The findings were published in the Journal of Clinical Psychiatry.