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Research suggests relationship between Toxoplasma gondii parasite, aggression

Recent findings provide further evidence of an association between Toxoplasma gondii — a parasite found in undercooked meat and cat feces — and aggression.

“Our work suggests that latent infection with the Toxoplasma gondii parasite may change brain chemistry in a fashion that increases the risk of aggressive behavior,” study researcher Emil F. Coccaro, MD, of the Pritzker School of Medicine, University of Chicago, said in a press release. “However, we do not know if this relationship is causal, and not everyone that tests positive for toxoplasmosis will have aggression issues.”

Emil Coccaro

To assess associations between latent T. gondii infection and aggression, researchers collected immunoglobulin G (IgG) antibodies to T. gondii from 358 adults with DSM-5 intermittent explosive disorder, psychiatric disorders other than intermittent explosive disorder and healthy controls. Antibodies were collected between 1991 and 2008.

T. gondii seropositive status — defined by researchers as IgG greater than 12 IU — was associated with higher aggression (P = .022) and impulsivity (P = .05).

When controlling for aggression and impulsivity scores, only aggression scores were higher in seropositive participants (P = .011).

T. gondii seropositive status and marginal mean aggression scores increased from healthy controls (9.1%; –0.66) to participants with non-intermittent explosive disorder psychiatric disorders (16.7%; –0.27) to participants with intermittent explosive disorder (21.8%; 1.15; P .05).

These findings were not accounted for by other syndromal/personality disorders or by states or traits related to depressive or anxious moods, according to researchers.

“It will take experimental studies to see if treating a latent toxoplasmosis infection with medication reduces aggressiveness,” Coccaro said in the release. “If we can learn more, it could provide rationale to treat [intermittent explosive disorder] in toxoplasmosis-positive patients by first treating the latent infection.” – by Amanda Oldt

Disclosure: Coccaro reports being a consultant, serving on the scientific advisory board and having stock options at Azevan Pharmaceuticals. Please see the full study for a list of all authors’ relevant financial disclosures.