A relatively harmless parasite infection may play a role in causing some people to lash out with impulsive anger, such as in cases of road rage.
Toxoplasmosis is found in around 30 per cent of all people and has been usually dismissed as insignificant. But now, scientists at the University of Chicago have linked the parasite to increased aggression.
“Our work suggests that latent infection with the toxoplasma gondii parasite may change brain chemistry,” said Professor Emil Coccaro.
The parasite is transmitted through the faeces of infected cats, undercooked meat or contaminated water. People diagnosed with intermittent explosive disorder (IED) were more than twice as likely to have been exposed to toxoplasmosis than people without the disorder.
IED affects more people than bipolar and schizophrenia combined and is characterised by recurring and impulsive outbursts of verbal or physical aggression that far outweigh the triggers.
But the researchers warn against rushing to judgement.
“Correlation is not causation, and this is definitely not a sign that people should get rid of their cats,” said study co-author Royce Lee. “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.”