Intermittent explosive disorder (IED) is defined in DSM-IV as several discrete episodes of failure to resist aggressive impulses that result in serious assaultive acts or destruction of property (criterion A). Also, the degree of aggression expressed during an episode is grossly out of proportion to any precipitating psychosocial stressors (criterion B) and the explosive episodes are not better accounted for by another mental disorder or due to the direct physiological effects of a substance or a general medical condition (criterion C). Varying definitions of IED based on the DSM-IV criteria have been proposed and used.^(4,5) One important set of research criteria for IED, for example, allows for less severe aggressive episodes, such as recurrent verbal outbursts against others without physical aggression, but requires that the aggressive episodes be recurrent and associated with distress or dysfunction.⁽⁴⁾ Although ICD-10 lists IED under ‘Other habit and impulse disorders’, it does not provide specific criteria for its diagnosis.

Regarding phenomenology, persons with IED describe their aggressive episodes as explosive, uncontrollable, unpremeditated, and brief; often provoked by minor stimuli; and associated with various psychological and physical symptoms, especially changes in mood, awareness, and autonomic arousal.^(4,6) The frequency of
episodes depends in part on how the disorder is defined. In the National Comorbidity Survey Replication (NCS-R), where the DSM-IV A criteria of ‘several’ episodes was operationalized to be three or more lifetime attacks, persons with IED had a mean of 43 lifetime attacks.

Many persons with IED describe problems with chronic or trait anger and frequent ‘subthreshold’ aggressive episodes in which they manage to resist enacting aggressive impulses or express them with less destructive behaviours (e.g. screaming rather than assault).^(4,6) These subthreshold episodes are similar to the anger attacks (sudden episodes of intense anger with autonomic arousal) often described in patients with mood (bipolar and depressive) disorders.⁽⁷⁾

Of note, the relationship between IED specifically and impulsive aggression in general remains unclear and the two phrases are not necessarily synonymous. In particular, like other impulse control disorders, the aggression of IED usually involves elements of lack of control (e.g. compulsivity) and affect dysregulation (extreme anger, irritability and/or mood instability) as well as impulsivity. Thus, IED may be one form of impulsive aggression.

Once thought to be rare, recent research has shown that IED is common in both clinical and general population samples. In the most rigorous study to date, the NCS-R, lifetime and 12-month prevalence estimates of DSM-IV IED in the general population were 7.3 per cent and 3.9 per cent, respectively.⁽⁵⁾ The lifetime and 12-month prevalences of more narrowly defined IED (in which three episodes in the same year were required for diagnosis) were 5.4 per cent and 3.5 per cent, respectively. The disorder is also likely to be common in forensic populations but data are not available.

IED is probably more common in males than females. In the NCS-R, 9.3 per cent of men versus 5.6 per cent of women met lifetime DSM-IV criteria for the disorder. IED begins in childhood or adolescence; follows a chronic or episodic course; and is associated with distress, morbidity (e.g. injuries), and social and occupational impairment.^{(4, 5 and 6)} For example, in the NCS-R, IED had a mean age of onset of 14 years, was persistent over the life course (with averages of 6.2-11.8 years with attacks), and was associated with substantial role impairment.⁽⁵⁾ However, the prevalence of the disorder was significantly lower among persons 60 years and older (2.1 per cent).

IED often co-occurs with other psychiatric disorders.^{(4, 5 and 6)} In the NCS-R, 81.8 per cent of respondents with lifetime DSM-IV IED met criteria for at least one other lifetime DSM-IV disorder. Specifically, IED was significantly comorbid with all DSM-IV depressive, anxiety, and substance use disorders assessed after controlling for age, sex, and race. It was also significantly comorbid with oppositional defiant disorder, conduct disorder, and attentiondeficit/hyperactivity disorder.

Importantly, the boundaries between IED and other conditions characterized by episodic and/or impulsive aggression have not been clearly delineated. Indeed, the comorbidity between IED and both bipolar disorders and Axis II disorders was not assessed in the NCS-R.⁽⁵⁾ Comorbidity with Axis II disorders was not determined because the prevalence of these disorders was not evaluated. Comorbidity with bipolar disorders was not assessed because of how IED was defined; cases of IED with lifetime mania or hypomania were excluded from analysis (number not specified) so that the prevalence of IED was not overestimated by cases of bipolar disorder with anger attacks. Of note, although the relationships between IED and both bipolar and cluster B personality disorders remain unclear, clinical studies suggest that patients with IED have high rates of these conditions.^(4,6)

Family studies suggest that relatives of probands with IED have high rates of impulsive violent behaviour, substance abuse, and possibly mood and other impulse control disorders.^(4,6,8,9) In a family history study of patients with temper outbursts meeting the first two DSM-III criteria for IED, non-adopted patients were significantly more likely than adopted patients to have a family history of temper outbursts.⁽⁹⁾ Of 25 subjects with DSM-IV IED evaluated via the family history method, 8 (32 per cent) of subjects had a first-degree relative with probable IED, 20 (80 per cent) had at least one first-degree relative with a substance use disorder, 14 (56 per cent) a mood disorder, and 14 (56 per cent) an impulse control disorder.⁽⁶⁾ A blinded, controlled family history study using broadly-defined IED criteria found a significantly increased morbid risk of the condition in relatives of affected probands (26 per cent) compared with relatives of control probands (8 per cent).⁽⁴⁾

Persons with impulsive aggression have been consistently found to have abnormalities in serotonergic function.⁽⁴⁾ Although most studies included subjects with impulsive aggression and personality disorders, a few included persons with IED or possible IED. Thus, in a study of 58 violent offenders and impulsive fire-setters, 33 (57 per cent) of whom had DSM-III IED, lower cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA) were found in the impulsive offenders and fire-setters than in the non-impulsive offenders and normal control subjects.⁽¹⁰⁾

In a functional magnetic resonance imaging (MRI) study of response to social threat, 10 subjects with IED showed exaggerated amygdala reactivity and diminished orbitofrontal cortex activation to faces expressing anger compared with controls.⁽¹¹⁾ The authors noted these findings were similar to other disorders characterized by impulsive aggression, including borderline personality and bipolar disorders, and that they supported a link between a dysfunctional frontal-limbic network and aggression.

Clinical experience suggests that IED may be less responsive to insight-oriented and more responsive to cognitive behavioural therapies, particularly those stressing anger management.^(4,6,12) Medications reported effective in definite or probable IED, some in controlled trials, include antiepileptics (e.g. phenytoin, carbamazepine, oxcarbazepine), antidepressants (e.g. tricyclics, serotonin reuptake inhibitors), mood stabilizers (e.g. lithium, valproate), β-blockers, psychostimulants, and even antiandrogens. Mood stabilizer monotherapy and antidepressant augmentation of mood stabilizers have both been reported to successfully treat IED and/or anger attacks in patients with bipolar disorders.^(6,7) Antidepressants have been reported to be effective in anger attacks associated with
major depression.⁽¹²⁾ Finally, serotonin reuptake inhibitors, mood stabilizers, antiepileptics, and antipsychotics may be effective for impulsive-aggressive behaviour in personality-disordered patients.⁽¹³⁾

Kleptomania is defined in DSM-IV as follows:

In ICD-10, kleptomania (or pathological stealing) is defined as the repeated failure to resist impulses to steal objects that are not acquired for personal use or monetary gain.

An increasing number of studies have systematically examined the phenomenology of groups of people with DSM-defined kleptomania.^{(14, 15, 16 and 17)} In these studies, most subjects described irresistible impulses or urges to steal, tension with the impulses, and tension relief either during or shortly after the act of theft (as required by the DSM criteria). Many subjects described the impulses as senseless, intrusive, uncomfortable, and uncontrollable. Many tried to resist the impulses with varying degrees of success. Some reported pleasurable feelings during the act of theft, often described as ‘a rush,’ ‘a high,’ or ‘a thrill.’ Most patients reported instances of impulsive stealing, but some also described premeditated stealing, the aim of which was sometimes to relieve the impulses to steal. Many subjects reported that they had lied to conceal their stealing. Some subjects developed rules for their stealing behaviour—for instance, stealing only from work or from certain types of shops (e.g. drug stores but not department stores), or stealing certain items but not others (e.g. jewellery but not clothing). Many subjects considered their stealing to be wrong, and many, but not all, reported guilt or remorse after stealing. Subjects who had been arrested for shoplifting reported that it had varying effects on their symptoms—some stopped stealing completely, some stopped for a limited amount of time, while others reported that their stealing was unaffected. Some stated they continued to steal once incarcerated.

These studies have also found that some subjects with apparent kleptomania report varying degrees of amnesia surrounding the act of stealing.⁽¹⁷⁾ Many of these subjects deny impulses, tension, or relief with their thefts. Other subjects who are not amnesiac for their stealing episodes may also deny experiencing impulses, tension, relief, and/or pleasure. For these subjects, stealing appears to have become automatic or habit-like.⁽¹⁷⁾

Kleptomania is presumed to be rare but its prevalence is unknown. Available studies suggest that only a small portion of shoplifters (from none to 8 per cent) represent true cases of kleptomania.⁽¹⁴⁾ However, it has been argued that these rates may be spuriously low because psychiatric evaluations may not have always been sufficiently thorough, operational diagnostic criteria were rarely used, and kleptomania may have been under-represented in the samples due to selection bias (i.e. people with repeated apprehensions were more likely to be legally rather than psychiatrically referred). Also, kleptomania may be relatively common in clinical populations; it was the second most common lifetime impulse control disorder in a group of adult psychiatric inpatients assessed with a structured interview, present in 9.3 per cent of the sample.⁽¹⁸⁾

Kleptomania is probably more common in women than in men.^{(14, 15, 16 and 17)} Many cases begin in adolescence or early adulthood, and often follow an episodic or a chronic course.

Clinical studies show that kleptomania often co-occurs with other Axis I psychiatric disorders, including mood, anxiety, substance use, eating, and impulse control disorders.^{(14, 15, 16, 17 and 18)} In the only controlled study,⁽¹⁶⁾ 10 patients with kleptomania had significantly higher rates of comorbid psychiatric disorders, particularly mood disorders, other impulse control disorders, and substance abuse or dependence (mainly nicotine dependence), than 29 psychiatric comparison patients and 60 patients with alcohol abuse or dependence. Several studies, including the one controlled study, found especially high rates of bipolar disorders.^{(15, 16 and 17)} Conversely, high rates of kleptomania have been found in women with eating disorders⁽¹⁴⁾ and patients with depressive disorders.⁽¹⁹⁾

Preliminary data suggest patients with kleptomania may also have high rates of certain Axis II disorders.⁽¹⁷⁾ However, the relationship between kleptomania and antisocial personality disorder is not understood.

Uncontrolled studies suggest kleptomania may be associated with increased familial rates of mood, substance use, anxiety, and possibly impulse control disorders.⁽¹⁷⁾ For example, of 103 first-degree relatives of 20 patients with DSM-IIIR-defined kleptomania evaluated blindly by the family history method, 22 (21 per cent) had a major mood disorder, 21 (20 per cent) had a substance use disorder, and 13 (13 per cent) had an anxiety disorder, including seven (7 per cent) with obsessive compulsive disorder⁽¹⁵⁾ Also, two (2 per cent) had apparent kleptomania. However, a controlled family study found similar rates of kleptomania in first-degree relatives of probands with obsessive compulsive disorder and those of control probands.⁽²⁰⁾

Preliminary research suggests kleptomania may be associated with serotonergic and frontal lobe dysfunction. In one study, the number of platelet serotonin transporters, evaluated via [3H] paroxetine binding, was lower in 20 patients with obsessive-compulsive related disorders, including five patients with kleptomania, than in 20 healthy control subjects.⁽¹⁷⁾ In another study, 10 females with DSM-IV kleptomania were more likely than controls to have decreased white matter microstructural integrity in inferior frontal brain regions when evaluated with diffusion tensor imaging.⁽²¹⁾

Although no controlled psychological treatment studies of kleptomania have been published, various types of cognitive behavioural therapy may be effective.^(12,17) There are also successful reports of the use of psychodynamic psychotherapies, but there are negative reports as well.^(12,15)

Medical treatments with antidepressant, mood-stabilizing, or anxiolytic properties have been reported to be effective in kleptomania, primarily in case reports and case series. These treatments include tricyclics, serotonin reuptake inhibitors, trazodone, lithium, valproate, electroconvulsive therapy, and benzodiazepines.^(12,15,17) There are also reports of patients with kleptomania responding to the opioid antagonist naltrexone and the antiglutamatergic agent topiramate.^(12,17)

However, in the only controlled pharmacotherapy study of kleptomania published to date, an open-label trial of escitalopram treatment in 24 subjects followed by double-blind discontinuation in 15 of 19 responders, there was no difference in response rate (defined as greater than a 50 per cent decrease in theft episodes per week) between subjects receiving escitalopram (3 [43 per cent]) and those receiving placebo (4 [50 per cent]).⁽²²⁾