Remember the motorist who was so upset at your driving that he pulled up next to you in traffic, blew his horn, pounded on the steering wheel, and cursed?
A lot of people simply might label him a jerk. The psychiatry profession takes a different view.
If the driver yells and pounds often enough, he could have intermittent explosive disorder (IED), a formal mental condition characterized by uncontrolled bouts of verbal or physical anger that are out of proportion to whatever triggered the outburst.
According to some published studies, up to 16 million U.S. adults -- or 7.3% of the population -- have had it at some point in their lives. And the rate in any given year is an estimated 3.9%.
Yet one of the researchers who came up with the figure a decade ago says he now is uncertain about it.
"I think it is very safe to say it is either more or less or the same," said Ronald Kessler, MD, the lead author of the 2006 paper that established the figures and a professor of healthcare policy at Harvard Medical School.
"In other words, who the hell knows?"
Another survey found a dramatically lower rate of the disorder.
Instead of being a condition that affects millions, the National Survey on Drug Abuse and Health found an annual rate of just 0.4%, or 911,000 adults. It was based on diagnostic surveys conducted by clinicians between 2008 and 2012.
Whatever the number, formalizing the condition as a mental disorder is way to rationalize bad behavior, said Joseph Wyatt, PhD, an emeritus professor of psychology at Marshall University.
"It is nothing more than grown-up tantrums," he said. "It is not something that people have. It is something that people do."
Wyatt has written about the medicalization of behavior, which he said can lead to the prescribing of drugs that often don't work well and can have serious side effects.
The FDA has not approved any medicine to treat intermittent explosive disorder, but that may change.
Azevan Pharmaceuticals is testing a drug for the condition in an 8-week trial involving about 100 people ages 21 to 55. The study was started in May 2014 and is expected to be completed this month…
Should the drug ultimately win FDA approval, it has the potential to be a blockbuster, said psychiatrist Emil Coccaro, MD, a consultant to the company. Blockbusters generally are defined as drugs that produce annual sales of more than $1 billion.
Coccaro, a professor of psychiatry at the University of Chicago who has authored more than 30 papers on the condition, said not only is intermittent explosive disorder real, it is as common as many other psychiatric disorders.
He said research shows that people with the condition have different brain structures. The condition also can be passed through genes, he said.
"Any behavior that gets you in trouble like that is a real disorder," he said.
"You see this with all mental disorders," said Joel Paris, MD, a professor of psychiatry at McGill University in Montreal and author of the book Prescriptions for the Mind: A Critical View of Contemporary Psychiatry.
"Every time they revise the manual, if they redefine it at all, they redefine it in a way that more people have it."
Consider what happened with intermittent explosive disorder.
The 1994 definition required at least three instances of physical aggression directed at property or people in an individual's lifetime.
In the 2013 manual, the definition was changed so that verbal aggression alone was enough, provided it occurred at least twice a week over a period of 3 months. But it also reduced the timeframe for physical aggression from a lifetime to three acts in a single year.
It is not known how many people qualify under the new definition; no new survey has been done.