Individuals with intermittent explosive disorder (IED) — a mental condition characterized by impulsivity, hostility and recurrent aggressive outbursts — have higher levels of two inflammation markers in their blood, according to a new study.
The study, published in the journal JAMA Psychiatry, is the first to show a direct link between inflammatory markers and recurrent, problematic, impulsive aggression in people diagnosed with intermittent explosive disorder, but not in those with good mental health or with other mental health disorders.
“These two markers consistently correlate with aggression and impulsivity but not with other psychiatric problems,” said senior study author Emil Coccaro, M.D., the Ellen C. Manning professor and chairman of the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago.
“We don’t yet know if the inflammation triggers aggression or aggressive feelings set off inflammation, but it’s a powerful indication that the two are biologically connected, and a damaging combination.”
Sufferers of IED overreact to stressful situations, often with uncontrollable anger and rage. IED outbursts are out of proportion to the situation that is triggering them.
Such blow-ups may at first be written off by others as “simple bad behavior,” Coccaro said, “but intermittent explosive disorder goes beyond that. It has strong genetic and biomedical underpinnings.
“This is a serious mental health condition that can and should be treated.”
IED can predispose people to other mental illnesses as well, including depression, anxiety, and alcohol or drug-abuse. Those with IED also have an increased risk for non-behavioral health issues, including coronary heart disease, hypertension, stroke, diabetes, arthritis, ulcers, headaches and chronic pain, according to a 2010 study.
For the study, researchers focused on blood levels of two markers of inflammation — C-reactive protein (CRP) and interleukin-6 (IL-6) — each of which has been associated with impulsive aggressive behaviors in humans, cats and mice.
CRP is produced by the liver in response to an infection or injury and helps focus the immune system’s attention on dead or damaged cells. IL6 is secreted by white blood cells to stimulate immune responses, such as fever and inflammation. It also increases production of CRP.
The researchers measured CRP and IL6 levels in 197 physically healthy volunteer subjects. Sixty-nine of these participants had been diagnosed with IED, 61 had been diagnosed with psychiatric disorders not involving aggression, and 67 had no mental disorder.
On average, both CRP and IL-6 levels were higher in subjects with IED, compared to either psychiatric or normal controls. In fact, average CRP levels were twice as high for those with IED as for normal healthy volunteers.
Both markers were particularly elevated in participants who had the most extensive histories of aggressive behavior. Each marker independently correlated with aggression, the authors said, suggesting that “both have unique relations with aggression.”
Previous research has pointed to connections between an inflammatory response and depression or stress, said Coccaro. Healthy people who have been exposed to endotoxins — which set off a powerful immune reaction — have a much stronger brain reaction to exposure to social threat, such as photographs of an angry or fearful face, than those who were not exposed to endotoxin.
Source: JAMA Psychiatry