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A mental disorder whose symptoms include lashing out in aggressively verbal or violent ways has recently been found to be nearly twice as common as previously thought. The research has sparked debate within the psychological community about the diagnosing of a mental illness whose symptoms overlap with normal, if undesirable, human behaviors, as well with as symptoms of other disorders.

Intermittent explosive disorder (IED), which is characterized by flying off the handle and overreacting to stress, was first recognized by the American Psychiatric Association in 1980. Now, as the Diagnostic and Statistical Manual of Mental Disorders (DSM), which is the book psychologists use when making diagnoses, is undergoing evaluation and revision, some are calling for new criteria to be used in identifying IED and other related disorders.

The next edition of the book, the DSM-V, is planned to be released in May 2013, almost 20 years after the last edition, the DSM-IV, was published in 1994.

"IED is a behavioral disorder that is a medical condition in the same way that depression or panic disorder is — it is not simply 'bad behavior,'" said Emil F. Coccaro, a professor of psychiatry and behavioral neuroscience at the University of Chicago. "Aggressive behavior is under genetic influence and IED runs in families."

How common?

It's not clear how many people have IED. The DSM-IV states that "reliable information is lacking, but Intermittent Explosive Disorder is apparently rare." However, others say IED is much more common than previously thought.

A 2004 study of 253 Baltimore residents estimated that 4 percent of people develop the disorder at some point during their lives. But according to a 2006 study published in the Archives of General Psychiatry, "Depending upon how broadly it is defined, this disorder affects as many as 7.3 percent of adults, or 16 million Americans, in their lifetimes."

The reason one study found IED to be nearly twice as prevalent as the other, Coccaro said, was in part due to gray areas in the diagnosis guidelines.

"The disorder was under-diagnosed," Coccaro said. "The proposed changes will lead to it being diagnosed to a more correct degree."

One problem with the current criteria is that they don't clearly delineate the severity level or the frequency of aggressive outbursts that define IED, said Coccaro.

"Looking at the criteria as written, having only three aggressive outbursts in one’s life could give you the diagnosis," Coccaro said. "However, people with only a few aggressive outbursts in their life do not look that different from other people. You really need to see much more frequent outbursts whether they involve very severe aggression or not."

Coccaro said that the criteria should require that a person has had three episodes involving physical assault against other people or destruction of property within one year, with a degree of aggressiveness "grossly out of proportion" to the situation. Also, the aggressive behavior should not have been committed to achieve a logical goal, such as attaining someone's money.

The criteria should also be written so that doctors diagnosing IED must rule out that the anger attacks, as they are sometimes called, aren't related to other mental disorders that also involve problems of impulse control, such as antisocial personality disorder, conduct disorder and schizophrenia, Coccaro said.

Anger attacks

According to the current criteria, a "blow up" occurs when a person with IED becomes enraged and fails to resist their aggressive impulses. They may strike or otherwise hurt another person, threaten to hurt someone, or destroy property, according to the DSM-IV.

"Typically, these people perceive a slight when none was meant and they 'blow up,' or they get frustrated by something, or by a rejection, and they 'blow up,' "said Coccaro.

During an anger attack, a person with IED expresses a degree of hostility that is grossly out of proportion to any sudden psychosocial stressors. The explosive behavior is often preceded by a sense of tension and is immediately followed by a sense of relief. After the episode, a person with IED may feel upset, remorseful, regretful, or embarrassed about their aggressive behavior, according to the DSM-IV.

Road rage, domestic abuse, and angry outbursts or temper tantrums that involve throwing or breaking objects may be signs of IED, according to the Mayo Clinic. According to Coccaro and other researchers, treatment for IED may involve medication, such as Prozac, and psychotherapy to help control aggressive impulses. People with the disorder have been shown to responds positively to a combination of both.

Improving the criteria, Coccaro said, may further increase the number of people diagnosed with IED.

"The criteria in DSM-III and IV were poorly set up and encouraged clinicians not to make the diagnosis if the patients seemed to be generally impulsive or aggressive,” Coccaro told Life's Little Mysteries.

Beyond IED

Confusing or inaccurate diagnosing guidelines are not as common as they used to be in the DSM, Coccaro said, but still exist. As more research is done on any disorder, it becomes better understood and defined more accurately. While some aspects of anger-related disorders remain mercurial, ongoing research has helped to bring data and awareness to the problems that exist.

How IED and other disorders will be defined in the upcoming edition of the DSM is still in question, as the DSM Task Force considers the comments and opinions of health professionals, patients, professional societies and researchers regarding the current definition, classification and diagnosing standards.

"There have been discussions about whether IED will change in the DSM-V, but no decisions have been made yet," Jaime Valora, a spokesperson for the American Psychiatric Association, told Life's Little Mysteries.

Still, Coccaro is hopeful that those revising the DSM will consider his research's findings so that the latest edition of the manual can be used to more accurately diagnose people.

"Typically, changes are due to better data about a disorder that makes the writers and editors of the DSM make changes in the criteria," Coccaro said.

This article was provided by LifesLittleMysteries, a sister site to LiveScience.