Intermittent Explosive Disorder (IED)

Intermittent Explosive Disorder (IED) is an impulse control disorder characterized by aggressive outbursts that has a rapid onset and, typically, with little to no warning.^[1] Outbursts typically last for less than 30 minutes, and usually occur in response to a minor provocation (usually by a friend or family member).^[2]

• In the United States, the 1-year prevalence data for IED is 2.7%.^[3]
  • In Asia, the Middle East, Romania, and Nigeria, rates are much lower, suggesting cultural factors as well in the presentation of IED.^[4]
• It is more prevalent in younger individuals (e.g. - <35-40 years), compared with older individuals (>50 years), and more common in individuals with a high school education or less.^[5]
• Some studies have shown males outnumber females for IED.^[6]

• The onset of IED symptoms usually develop late childhood or adolescence and rarely begins for the first time after age 40.
• The core symptoms of IED are usually chronic, persistent, and continue for many years.^[7]
  • IED may be episodic, punctuated by recurrent periods of impulsive aggressive outbursts.
• Individuals will often have social (e.g. - loss of friends, marriage), occupational (e.g. - loss of employment), financial (e.g. - due to value of objects destroyed), and legal (e.g. - lawsuits as a result of aggressive behaviour against person or property; criminal charges for assault) impairment.

• Depressive disorders, anxiety disorders, and substance use disorders are associated with IED.^[8]
• Individuals with antisocial or borderline personality disorder, ADHD, conduct disorder, and oppositional defiant disorder are also more likely to have IED.^[9]

• Individuals with a history of adverse childhood events are at increased risk for IED.^[10]
• First-degree relatives of individuals with IED are also at increased risk for IED themselves
  • Twin studies have shown a significant genetic influence for impulsive aggression.^[11]

Recurrent behavioural outbursts representing a failure to control aggressive impulses as manifested by either of the following:

1. Verbal aggression (e.g. - temper tantrums, tirades, verbal arguments or fights) or physical aggression toward property, animals, or other individuals, occurring twice weekly, on average, for a period of 3 months. The physical aggression does not result in damage or destruction of property and does not result in physical injury to animals or other individuals.
2. 3 behavioural outbursts involving damage or destruction of property and/or physical assault involving physical injury against animals or other individuals occurring within a 12-month period.

The magnitude of aggressiveness expressed during the recurrent outbursts is grossly out of proportion to the provocation or to any precipitating psychosocial stressors.

The recurrent aggressive outbursts are not premeditated (i.e. - they are impulsive and/or anger-based) and are not committed to achieve some tangible objective (e.g. - money, power, intimidation).

The recurrent aggressive outbursts cause either marked distress in the individual or impairment in occupational or interpersonal functioning, or are associated with financial or legal consequences.

Chronological age is at least 6 years (or equivalent developmental level).

The recurrent aggressive outbursts are not better explained by another mental disorder (e.g. - major depressive disorder, bipolar disorder, disruptive mood dysregulation disorder, a psychotic disorder, antisocial personality disorder, borderline personality disorder) and are not attributable to another medical condition (e.g. - head trauma, Alzheimer’s disease) or to the physiological effects of a substance (e.g. - a drug of abuse, a medication). For children ages 6 to 18 years, aggressive behaviour that occurs as part of an adjustment disorder should not be considered for this diagnosis.

• Regardless of the nature of the aggressive outburst, it is the failure to control impulsive and aggressive behaviour in response to a subjectively experienced provocation (i.e. - a psychosocial stressor) that defines IED.
• Furthermore, the aggressive outbursts are generally impulsive and/ or anger-based, rather than premeditated or instrumental (e.g. - as might be seen in conduct disorder).

• Serotonergic changes in the limbic system (anterior cingulate) and orbitofrontal cortex are seen in IED.^[12]
• On fMRI, the amygdala responses to anger stimuli are greater in individuals with IED.^[13]

• A diagnosis of IED should not be made when Criteria A1 and/or A2 are only met during an episode of another mental disorder (e.g. - major depressive disorder, bipolar disorder, psychotic disorder), or when the outbursts are attributable to another medical condition or to the physiological effects of a substance or medication. This diagnosis also should not be made, particularly in children and adolescents ages 6 to 18 years, when the impulsive aggressive outbursts occur in the context of an adjustment disorder. Other examples in which recurrent, problematic, impulsive aggressive outbursts may, or may not, be diagnosed as IED include the following:
  • Disruptive mood dysregulation disorder (DMDD)
    • In contrast to IED, DMDD is characterized by a persistently negative mood state (i.e. - irritability, anger) most of the day, nearly every day, even between impulsive aggressive out bursts. DMDD can only be diagnosed when the onset of recurrent, problematic, impulsive aggressive outbursts is before age 10 years. Finally, a diagnosis of DMDD should not be made for the first time after age 18 years. Otherwise, these IED and DMDD are mutually exclusive diagnoses.
  • Antisocial personality disorder or borderline personality disorder
    • Individuals with antisocial or borderline personality disorder often have recurrent, problematic impulsive aggressive outbursts. However, the level of impulsive aggression in individuals with antisocial or borderline personality disorder is lower than that in individuals with IED.^[14]
  • Delirium, major neurocognitive disorder, and personality change due to another medical condition, aggressive type
    • IED should not be diagnosed when aggressive outbursts are a result from the physiological effects of another medical condition (e.g. - traumatic brain injury associated with a change in personality characterized by aggressive outbursts; complex partial epilepsy). Nonspecific abnormalities on neurological examination (e.g. - “soft signs”) and nonspecific electroencephalographic (EEG) changes are compatible with a diagnosis of IED unless there is a diagnosable medical condition that better explains the outbursts.
  • Substance intoxication or substance withdrawal
    • IED should not be diagnosed when impulsive aggressive outbursts are nearly always associated with intoxication or withdrawal from substances (e.g. - alcohol, phencyclidine, cocaine, barbiturates, inhalants). When a number of outbursts also occur in the absence of substance intoxication or withdrawal, and these warrant independent clinical attention, an additional diagnosis of IED may be given.
  • Attention-deficit/hyperactivity disorder, conduct disorder, oppositional defiant disorder (ODD), or autism spectrum disorder (ASD)
    • Individuals with any of these childhood-onset disorders may exhibit outbursts. Individuals with ADHD are typically impulsive and, as a result, may also exhibit impulsive aggressive outbursts. While individuals with conduct disorder can exhibit impulsive aggressive outbursts, the aggression is proactive and predatory. Aggression in ODD is typically characterized by temper tantrums and verbal arguments with authority figures, whereas outbursts in IED are in response to a broader array of provocation and include physical assault.
    • The level of impulsive aggression in individuals with these above disorders are typically lower than that of IED. If the impulsive aggressive outbursts warrant independent clinical attention, then a diagnosis of intermittent explosive disorder may be given.

• Behavioural interventions are an important part of the treatment of IED.
• There are no approved pharmacological treatments for IED.
  • Mood stabilizers, antipsychotics, beta-blockers, alpha(2)-agonists, phenytoin and antidepressants may be useful.