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Does a Common Parasite Play a Role in Rage Disorder?

April 15, 2016

Teodor Postolache, MD

University of Maryland School of Medicine Study Finds Link Between Rage Disorder and Exposure to a Common Parasite


In recent years, a common parasitic infection has been linked to a range of psychiatric disorders, including schizophrenia and bipolar disorder, as well as suicide attempts. Now a new study has linked it to repeated bouts of rage, a disorder known as intermittent explosive disorder (IED).

The study, released recently in the Journal of Clinical Psychiatry, found that people with IED are more than twice as likely to have been exposed to a common parasite than healthy individuals with no psychiatric diagnosis.

“This is the first time we’ve confirmed this idea in humans,” said the senior author of the study, Teodor Postolache, MD, a Professor of Psychiatry at the University of Maryland School of Medicine (UM SOM). “It indicates that this parasite could be having significant effects on anger-related emotions and behavior in people with mental illness.”

The study was based on the combined expertise of the main authors, Emil Coccaro, MD, Chairman of the Department of Psychiatry at the University of Chicago, who is an expert on rage, and Dr. Postolache, who is an expert on T. gondii and neuroimmunology.

The study looked at 358 adults, and found that chronic latent infection with T. gondii is associated with intermittent explosive disorder and increased aggression. Those with IED have recurrent, impulsive, problematic outbursts of verbal or physical aggression that are disproportionate to the situations that trigger them. It affects as many as 16 million Americans.

Transmitted through the feces of infected cats, undercooked meat or contaminated water, chronic toxoplasmosis is typically latent and harmless for healthy adults. As many as a third of the world’s population may have it. However, Toxoplasma it is known to reside in slow growing forms in brain tissue, and has the potential to intermittently reactivate.

Subjects in the study were analyzed for personality traits, including anger, aggression and impulsivity. Participants fell into one of three groups: about a third had IED. A third were healthy controls with no psychiatric history. The remaining third were individuals diagnosed with some psychiatric disorder, but not IED. This last group served as a control to distinguish IED from other psychiatric factors.

The study found that the IED group was more than twice as likely to test positive for toxoplasmosis, compared to the healthy control group. Around 16 percent of the psychiatric control group tested positive for toxoplasmosis, but had similar aggression and impulsivity scores to the healthy control group. IED-diagnosed subjects scored much higher on both measures than either control group.

Dr. Coccaro and Dr. Postolache caution that the study results do not address whether Toxoplasma infection actually cause increased aggression or IED

Dr. Postolache and his colleagues are continuing their work on the relationship between Toxoplasma gondii, impulsivity and aggression in collaborations with researchers from Sweden (people who have recently attempted suicide) and Germany (aggression, impulsivity, and the neurotransmitter dopamine. If better understood, this connection may inform new strategies to predict and manage aggression and impulsivity, major factors implicated in violence towards self and others.

“Dr. Postolache’s work is a great example of how we are increasingly conducting translational research – where scientific inquiry informs us in a way that has relevant and direct clinical value,” said UM SOM Dean E. Albert Reece, MD, PhD, MBA, who is also the vice president for Medical Affairs, University of Maryland, and the John Z. and Akiko K. Bowers Distinguished Professor. “As we understand more and more about the brain, we can discover new ways to treat psychiatric disorders affecting large numbers of the population.”

About the University of Maryland School of Medicine

The University of Maryland School of Medicine was chartered in 1807 and is the first public medical school in the United States and continues today as an innovative leader in accelerating innovation and discovery in medicine. The School of Medicine is the founding school of the University of Maryland and is an integral part of the 11-campus University System of Maryland. Located on the University of Maryland’s Baltimore campus, the School of Medicine works closely with the University of Maryland Medical Center and Medical System to provide a research-intensive, academic and clinically based education. With 43 academic departments, centers and institutes and a faculty of more than 3,000 physicians and research scientists plus more than $400 million in extramural funding, the School is regarded as one of the leading biomedical research institutions in the U.S. with top-tier faculty and programs in cancer, brain science, surgery and transplantation, trauma and emergency medicine, vaccine development and human genomics, among other centers of excellence. The School is not only concerned with the health of the citizens of Maryland and the nation, but also has a global presence, with research and treatment facilities in more than 35 countries around the world.


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