Intermittent explosive disorder is more common than previously thought

A little-known mental disorder marked by episodes of unwarranted anger is more common than previously thought, a study funded by the National Institutes of Health's (NIH) National Institute of Mental Health (NIMH) has found.

Depending upon how broadly it's defined, intermittent explosive disorder (IED) affects as many as 7.3 percent of adults - 11.5-16 million Americans - in their lifetimes. The study is based on data from the National Comorbidity Survey Replication, a nationally representative, face-to-face household survey of 9,282 U.S. adults, conducted in 2001-2003.

People with IED may attack others and their possessions, causing bodily injury and property damage. Typically beginning in the early teens, the disorder often precedes - and may predispose for - later depression, anxiety and substance abuse disorders. Nearly 82 percent of those with IED also had one of these other disorders, yet only 28.8 percent ever received treatment for their anger, report Ronald Kessler, Ph.D., Harvard Medical School, and colleagues. In the June, 2006 Archives of General Psychiatry, they suggest that treating anger early might prevent some of these co-occurring disorders from developing.

To be diagnosed with IED, an individual must have had three episodes of impulsive aggressiveness - grossly out of proportion to any precipitating psychosocial stressor, at any time in their life, according to the standard psychiatric diagnostic manual. The person must have - all of a sudden lost control and broke or smashed something worth more than a few dollars - hit or tried to hurt someone - or threatened to hit or hurt someone.

People who had three such episodes within the space of one year - a more narrowly defined subgroup - were found to have a much more persistent and severe disorder, particularly if they attacked both people and property. The latter group caused 3.5 times more property damage than other violent IED sub-groups. Affecting nearly 4 percent of adults within any given year - 5.9-8.5 million Americans - the disorder leads to a mean of 43 attacks over the course of a lifetime and is associated with substantial functional impairment.

Evidence suggests that IED might predispose toward depression, anxiety, alcohol and drug abuse disorders by increasing stressful life experiences, such as financial difficulties and divorce.

Given its earlier age-of-onset, identifying IED early - perhaps in school-based violence prevention programs - and providing early treatment might prevent some of the associated psychopathology, propose the researchers. Although most study respondents with IED 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.

Although the new prevalence estimates for IED are somewhat higher than previous studies have found, the researchers consider them conservative. For example, anger outbursts in people with bipolar disorder, which often overlaps with IED, were excluded. Previous studies have found little overlap between IED and other mental illnesses associated with impulsive violence, such as antisocial and borderline personality disorders.

Also participating in the study were Dr. Emil Coccaro, University of Chicago, Dr. Maurizio Fava, Massachusetts General Hospital, and Dr. Savina Jaeger, Robert Jin, and Ellen Walters, Harvard University.

In addition to primary funding from the NIMH, the National Comorbidity Survey Replication received supplemental funding from a number of sources, including National Institute on Drug Abuse (NIDA) and the Substance Abuse and Mental Health Services Administration (SAMHSA).