Given enough frustration, it’s normal and healthy to get angry. But for a subset of the U.S. population — some 7 percent of adults, according to the National Institute of Mental Health — the propensity to fly off the handle is so great that they can be professionally diagnosed with “Intermittent Explosive Disorder,” or IED. The disorder is marked by episodes of outsize anger, with the intensity of the response being way more than whatever the provocation warrants. If someone in your life is given to “road rage, domestic abuse, throwing or breaking objects, or other temper tantrums,” the Mayo Clinic says, then they may have IED.
And they may also, according to new neurological research coming out of the University of Chicago, have brains that predispose them to wrath. In a study in the journal Neuropsychopharmacology, a team lead by psychiatrist and behavioral neuroscientist Royce Lee found that people with IED — yes, that’s the same acronym for improved explosive device, a class of bombs favored by militants and terrorists — have less integrity in the white matter of the superior longitudinal fasciculus, an area of the brain that connects the frontal lobe — associated with emotions and decision-making — with the parietal lobe, which processes sensory information.
The results come from MRI scanning 132 adults: 42 of them had been diagnosed with IED, 50 were “psychiatric controls,” meaning they had other psychiatric disorders but not IED, and 40 were normal controls. They found that people with IED and also borderline personality disorder, which is marked by extremely unstable moods, had those poor brain connections.
“This is another example of tangible deficits in the brains of those with IED that indicate that impulsive aggressive behavior is not simply ‘bad behavior’ but behavior with a real biological basis that can be studied and treated,” Emil Coccaro, a co-author on the paper, said in a statement. In one sense, this is hopeful since treatments include prescriptions and cognitive behavioral therapy. But in another sense, saying that aggressive — and potentially emotionally, physically, and financially destructive — acts aren’t just the result of bad behavior seems to take the agency of the actor out of the situation. Would a claim of “my neural connections made me do it” hold up in a court of law? That’s the deeper question: Are you, the moral agent, responsible for the way your brain is built? It’s an inquiry beyond the realm of this study, but as science discovers more about what’s happening inside people’s skulls, the legal system is going to have to figure it out.