The seldom-studied psychiatric condition called intermittent explosive disorder, characterized by recurrent episodes of angry and potentially violent outbursts?seen in cases of road rage or spousal abuse?has been found to be much more common than previously thought, according to an article in the June issue of the Archives of General Psychiatry.

Depending upon definition, the disorder affects as many as 7.3 percent of adults, or 16 million Americans, in their lifetimes, and 4 percent, or 8.6 million Americans, per year, according to study coauthor Ronald Kessler, PhD, professor of health care policy at Harvard Medical School. The study also found that Intermittent Explosive Disorder may predispose people to other mental illnesses and substance abuse.

Intermittent Explosive Disorder attacks are out of proportion to the social stressors triggering them and are not due to another mental disorder or the effects of drugs or alcohol, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). People with this disorder overreact to situations with uncontrollable rage, feel a sense of relief during the angry outburst, and then feel remorseful about their actions.

The current study is based on data from the National Comorbidity Survey Replication (NCS-R), a nationally representative face-to-face household survey of 9,282 American adults, conducted from 2001 to 2003. The NCS-R is carried out in conjunction with the World Health Organization World Mental Health Survey Initiative.

Among people with this disorder, 81.8 percent also were diagnosed with depression, anxiety, and alcohol or drug abuse disorders, although the age of onset of Intermittent Explosive Disorder was usually much earlier than that of these other disorders.

“This suggests that people with this disorder may be more susceptible to other disorders because of increased stressful life experiences as a result of their disorder, such as financial difficulties or divorce,” said Kessler, noting this raises the possibility that Intermittent Explosive Disorder may be a risk factor for other mental disorders.

To be diagnosed with broadly-defined Intermittent Explosive Disorder, a person must have had three major episodes of impulsive aggressiveness at any time in his life where, according to the study, the person was significantly more angry than most people would have been in the same situation. These outbursts are sudden and include damage to property and/or physical harm (or threat of physical harm) to others.

A narrow definition of Intermittent Explosive Disorder includes three or more of these attacks in one year. In the study, people with narrow Intermittent Explosive Disorder had a more persistent and severe illness, particularly if they attacked both people and property, causing 3.5 times more property damage than other violent Intermittent Explosive Disorder subgroups.

The study shows that for both broad and narrowly-defined Intermittent Explosive Disorder, the first episode of rage occurred in early adolescence, around age 13 for males and age 19 for females. “Given its age of onset, identifying Intermittent Explosive Disorder early, determining its causes, and providing treatment might prevent some of the associated secondary disorders, such as anxiety or alcohol abuse,” noted Kessler.

Although most study respondents with the disorder had seen a professional for emotional problems at some time in their lives, only 11.7 percent had been treated for their anger in the 12 months prior to the study interview.

Effective treatment for Intermittent Explosive Disorder includes both behavioral and pharmacological interventions (selective serotonin reuptake inhibitors and mood stabilizers), said Emil Coccaro, MD, coauthor. “Ideally, people should be treated with both medicine and cognitive-behavioral therapy. Medicines increase the threshold at which people will explode, and cognitive-behavior therapy teaches people how to handle feelings of frustration or threat that often lead to explosive episodes.”