A Primer on Intermittent Explosive Disorder

Intermittent explosive disorder (IED) is characterized by recurrent, problematic, impulsive aggression. IED is now understood as being more common than previously thought.

According to the National Comorbidity Survey Replication, the lifetime prevalence of IED is 7.3% by “broad [DSM-IV] criteria” and 5.4% by “narrow criteria.”² “Narrow” IED requires at least three aggressive outbursts during a year, and is more severe than “broad” IED, which stipulates at least three aggressive outbursts during the course of a lifetime.³ Age of onset for males is typically earlier than for females, although women are as likely as are men to develop IED.⁴

IED has many comorbidities, including mood disorders, lifetime prevalence of anxiety disorders, personality disorders (especially antisocial and borderline), and substance abuse disorders.⁴ A significant percentage of individuals with IED have a history of childhood trauma.^5,6

Neurophysiologic Correlates of IED

The core behavior in IED is impulsive aggression, which is modulated by limbic brain structure — especially the amygdala and hippocampus. In borderline personality disorder and antisocial personality disorder, amygdala and hippocampal volume are reduced.

A recent study¹ using high resolution structural 3T magnetic resonance (MR) scans found that IED was associated with “localized, inwardly directed deformation in both the amygdala and hippocampus” and “significant loss of neurons in these brain regions” The authors concluded that these changes “may play a role in the functional abnormalities observed in previous fMRI studies and the pathophysiology of impulsive aggressive behavior.” Additionally, some studies suggest that individuals with IED have altered serotonin function, compared to individuals without IED.^7,8

Categorizing and Diagnosing IED

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) includes IED among impulse control disorders, marked by problems controlling emotions and behavior, which violate social norms as well as the rights of others.⁹

Table 1.

DSM-5 Diagnostic Criteria for Intermittent Explosive Disorder

Failure to control aggressive impulse that leads to behavioral outbursts, as manifested by either: Verbal aggression (eg, temper tantrums, tirades, arguments, or fights) or physical aggression directed toward property, animal or other individuals that does not result in physical damage or injury, with outbursts occurring on average at least twice weekly for three months Physical assaults that damage property or injure animals or other people, occurring at least three times in a 12-month period Aggressive behavior grossly out of proportion to the provocation or precipitating psychosocial stressors Behavior outbursts are not premeditated (ie, are impulsive or anger-based) and are not committed to achieve some tangible objective (eg, money, power, intimidation) Marked distress in the individual or impairment in occupational or interpersonal functioning, or associated with financial/legal consequences Chronological age ≥ six years Aggression not accounted for by another disorder.