Coccaro told Live Science he was intrigued by the body of scientific literature linking toxoplasmosis with psychiatric disorders. For this study, his research team recruited 358 adults. About one-third had IED, defined by the Diagnostic and Statistical Manual of Mental Disorders as recurrent, impulsive, problematic outbursts of verbal or physical aggression disproportionate to the situations that trigger them. Another one-third were individuals diagnosed with another psychiatric disorder (not IED). And the remaining third were healthy controls with no psychiatric history.
The research team found that 22 percent of the people with IED tested positive for toxoplasmosis exposure, compared with only 9 percent of the healthy control group. About 16 percent of the group with other psychiatric disorders tested positive for toxoplasmosis, too.