People who are prone to rage attacks have smaller “emotional brains,” according to a new study based on brain scans.

Researchers concluded that people with this condition, called intermittent explosive disorder, have less “gray matter”—brain tissue made of nerve cells—in the so-called frontolimbic regions of the brain, structures that regulate emotions.

These brain areas play an important role in the biology of aggressive behavior, according to scientists. An article on the new findings is published in the inaugural issue of the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.

The findings “suggest that disrupted development of the brain’s emotion-regulating circuitry may underlie an individual’s propensity for rage and aggression,” said the journal’s editor, Cameron Carter of the University of California, Davis.

Intermittent explosive disorder is defined as “recurrent, problematic, impulsive aggression,” explained Emil Coccaro of the University of Chicago, the article’s lead author.

“While more common than bipolar disorder and schizophrenia combined, many in the scientific and lay communities believe that impulsive aggression is simply ‘bad behavior’ that requires an ‘attitude adjustment.’”

But the new data confirm that the condition is “a brain disorder and not simply a disorder of ‘personality,’” he added. More generally, smaller frontolimbic gray matter volume correlates to more aggression, he said.

The investigators collected high-resolution brain scans in 168 people, including 57 subjects with the disorder, 53 healthy control subjects, and 58 psychiatric control subjects. Using the scans, taken with the technique known as magnetic resonance imaging, the researchers said they found a direct link between history of actual aggressive behavior and smaller gray matter volume.