Mr. P, age 41, has a “problem with anger.” Since age 17, he has had sudden outbursts of screaming and shouting, with occasional minor damage to objects. These outbursts—including episodes of “road rage”—occur once or more per week and almost daily for months at a time.
Mr. P has also had more violent episodes— sometimes every 2 to 3 months—in which he has punched holes in walls, destroyed a computer with a hammer, and assaulted other people with his fists. These events are not premeditated and are typically triggered by Mr. P’s frustration at not being “perfect” or by others breaking what he considers “general rules of conduct.”
The day before his initial visit, while he was stuck in traffic, Mr. P saw a car speeding down the shoulder. Enraged, he pulled in front of the car so that the driver had to slam on the brakes. He jumped out of his car and approached the other driver, shouting obscenities. The other driver locked her door and tried to ignore Mr. P until he returned to his car. Mr. P noted that this episode “ruined” his day because of his lingering anger and irritability.
Intermittent explosive disorder (IED) is more common and complex than was once thought, based on recent evidence. Recurrent, problematic, impulsive aggression is highly comorbid with other psychiatric conditions—including mood and personality disorders—and undermines social relationships and job performance. Typical characteristics of IED are outlined in Table 1.1-3
Table 1
Typical characteristics of intermittent explosive disorder
| Onset in childhood or adolescence (mean age 15), with average duration ±20 years |
| Aggressive outbursts: |
|
| Some episodes may appear without identifiable provocation |
| Male to female ratio 3:1, although some data suggest gender parity |
| Source: Adapted from references 1-3 |
This article offers updated diagnostic criteria and a two-pronged algorithm that can help you diagnose and treat this aggression disorder.
HOW COMMON IS IED?
DSM-IV states that IED is “apparently rare.” This statement is far from surprising, given the limitations of DSM criteria. Surveys of hospitalized patients in the 1980s found that only 1.1% met DSM-III criteria for IED.4 In another study of more than 400 patients seeking treatment for aggression, only 1.8% met DSM-III criteria for IED (although far more would likely have met DSM-IV criteria).5
A more recent survey of 411 psychiatric outpatients6 found that 3.8% met current and 6.2% met lifetime DSM-IV criteria for IED, using the Structured Clinical Interview for DSM-IV Diagnoses (SCID). Reanalysis of a threefold larger data set from the same study site (Coccaro and Zimmerman, unpublished) yielded the same result.
Far from rare. More recently, our findings from a small sample suggested that the community rate of lifetime IED is about 4% by DSM-IV criteria and 5% by research criteria. In the United States, we estimate that the lifetime rate of IED could be 4.5 to 18 million persons using DSM-IV criteria or 6.7 to 22.2 million using IED research criteria. If so, IED is at least as common as other major psychiatric disorders, including schizophrenia or bipolar illness. The ongoing National Comorbidity Study is expected to produce more definitive community data.
PSYCHIATRIC COMORBIDITY
Axis I disorders. IED is highly comorbid with mood, anxiety, and substance use disorders,3,7,8 although no causal relationship has been shown
Mood and substance abuse disorders. IED’s age of onset may precede that of mood and substance use disorders, according to analysis of our unpublished data. If so, comorbid IED may not occur in the context of mood or substance use disorders.
Anxiety disorders. We have noted a similar pattern with IED and anxiety disorders, although phobic anxiety disorders (simple or social phobia) tend to manifest earlier than IED. This suggests that early-onset phobic anxiety might be associated with an increased risk of IED in adolescence or young adulthood.
Bipolar disorder. McElroy9 has suggested a relationship between IED and bipolar disorder. In some samples, as many as one-half of IED patients (56%) have comorbid bipolar disorder when one includes bipolar II and cyclothymia.3 Moreover, some subjects’ aggressive episodes appear to resemble “microdysphoric manic episodes.”9 Other studies,8 however, find a much lower rate (10% or less) of IED comorbidity with bipolar illness.
Bipolar disorder overall may not be highly comorbid with IED, although rates may be higher in specialty clinic samples. In individuals with any kind of bipolar disorder, mood stabilizers— rather than selective serotonin reuptake inhibitors (SSRIs)—are probably the better choice as first-line treatment of IED.9