The onset of recurrent, problematic, impulsive aggressive behavior is most common in late childhood or adolescence and rarely begins for the first time after age 40 years. The core features of intermittent explosive disorder, typically, are persistent and continue for many years.
The course of the disorder may be episodic, with recurrent periods of impulsive ag— gressive outbursts. Intermittent explosive disorder appears to follow a chronic and persis— tent course over many years. It also appears to be quite common regardless of the presence or absence of attention-deficit/hyperactivity disorder (ADHD) or disruptive, impulse- control, and conduct disorders (e.g., conduct disorder, oppositional defiant disorder).
Environmental. Individuals with a history of physical and emotional trauma during the first two decades of life are at increased risk for intermittent explosive disorder.
468 Disruptive, Impulse-Control, and Conduct Disorders
Genetic and physiological. First-degree relatives of individuals with intermittent ex- plosive disorder are at increased risk for intermittent explosive disorder, and twin studies have demonstrated a substantial genetic inﬂuence for impulsive aggression.
Research provides neurobiological support for the presence of serotonergic abnormal- ities, globally and in the brain, specifically in areas of the limbic system (anterior cingulate) and orbitofrontal cortex in individuals with intermittent explosive disorder. Amygdala responses to anger stimuli, during functional magnetic resonance imaging scanning, are greater in individuals with intermittent explosive disorder compared with healthy indi- viduals.
The lower prevalence of intermittent explosive disorder in some regions (Asia, Middle
East) or countries (Romania, Nigeria), compared with the United States, suggests that in- formation about recurrent, problematic, impulsive aggressive behaviors either is not elic- ited on questioning or is less likely to be present, because of cultural factors.
In some studies the prevalence of intermittent explosive disorder is greater in males than in females (odds ratio = 1.4—2.3); other studies have found no gender difference.
Social (e.g., loss of friends, relatives, marital instability), occupational (e.g., demotion, loss of employment), financial (e.g., due to value of objects destroyed), and legal (e.g., civil suits as a result of aggressive behavior against person or property; criminal charges for as- sault) problems often develop as a result of intermittent explosive disorder.
A diagnosis of intermittent explosive disorder 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 impulsive aggressive 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 ado- lescents ages 6—18 years, when the impulsive aggressive outbursts occur in the context of an adjustment disorder. Other examples in which recurrent, problematic, impulsive ag- gressive outbursts may, or may not, be diagnosed as intermittent explosive disorder in- clude the following.
Disruptive mood dysregulation disorder. In contrast to intermittent explosive disorder, disruptive mood dysregulation disorder is characterized by a persistently negative mood state (i.e., irritability, anger) most of the day, nearly every day, between impulsive aggressive out- bursts. A diagnosis of disruptive mood dysregulation disorder can only be given when the on- set of recurrent, problematic, impulsive aggressive outbursts is before age 10 years. Finally, a diagnosis of disruptive mood dysregulation disorder should not be made for the first time after age 18 years. Otherwise, these diagnoses are mutually exclusive.