Most who brave the Los Angeles freeways have experienced the warm, fuzzy ministry of another motorist cutting into their lane while waving the international friendship sign. This can render even the most laid-back, Prius-driving, yoga master a bit testy.
But for a small number of people, this minor driving altercation will spark rage so profound, so visceral, that it leads to car chases, fisticuffs and maybe even a few nights in the slammer. Now researchers say these people may be suffering from a seldom-studied condition known as intermittent explosive disorder, a condition that could be twice as prevalent as thought.
New research suggests that, depending on how it is defined, the disorder may affect 7.3% of the adult population, or as many as 16 million Americans, in their lifetimes, according to a study led by Ronald Kessler, a professor of healthcare policy at Harvard Medical School. In a given year, nearly 4% of the population, or as many as 8.5 million Americans, may experience the disorder, says Kessler.
The findings, derived from a nationwide household survey of 9,282 adults conducted between February 2001 and April 2003, was reported in the June issue of Archives of General Psychiatry.
As characterized by the Diagnostic and Statistical Manual of Mental Disorders -- the standard diagnostic reference book for psychotherapists -- a person with intermittent explosive disorder has on several occasions been unable to resist aggressive impulses that result in serious harm to individuals or property; the degree of aggressiveness is "grossly out of proportion" to the situation; and the episodes are not better accounted for by another condition, such as ADHD, and are not due to the physiological effects of a drug or a general medical condition, such as head trauma or Alzheimer's.
In some cases, the episode may be preceded by heart palpitations, head pressure or hearing an echo.
In short, true intermittent explosive disorder leaves garden-variety freeway altercations in the dust. In fact, even bona fide road rage -- which tends to get the most air-time in the nightly news -- isn't how the disorder most often manifests itself.
More typical, says Kessler, is the person who gets furious at a spouse or child for a minor disagreement over something as mundane as dinner not being served on time or neglected chores.
"It's true that periodically you hear about someone beating someone up at a baseball game," says Kessler. "But much more common are the hidden cases where the victims are the spouse and kids."
Kessler and colleagues found that the disorder tends to appear in late childhood, or early teens, and that it is 40% more prevalent in males than in females.
Older respondents to the questionnaire were less likely to report having experienced it than respondents in their 20s. But because the study was based on self-reports, or remembrances of the participants, the disparity could be the result of faulty or selective memories, says Kessler.
Not everyone is convinced that the disorder is more common than previously believed.
Dr. Darrel Regier, director of research for the American Psychiatric Assn., believes that the questions in the survey may have teased out memories of relatively low-level episodes of violence or aggression. "This is an exceptional disorder with criteria that are hard to meet," he said. "The likelihood that 7% of the population would meet the criteria is not very high."
And further, some suggest that clinicians need to be careful about labeling clients with the disorder.
"I'm uneasy with the medicalization of this misbehavior," says Dr. Leonard Sax, a family physician and psychologist in Montgomery County, Md. The author of "Why Gender Matters," Sax believes that society is increasingly applying psychological labels to what he believes could be better characterized as bad behavior.
"Instead of saying, 'Hey, these people are misbehaving, they need to make better choices and take responsibility for their decisions,' we now say, 'Ah, this person has IED.' "
Nevertheless, other researchers say the problem is serious, underreported and under treated. "There are many people who have been struggling with violent outbursts and anger attacks and don't know why," says Maurizio Fava, professor of psychiatry at Harvard Medical School and coauthor of the study.