The purpose of the present study is to evaluate the prevalence of intermittent explosive disorder (IED) as well as its comorbidity with other mental disorders in a Japanese community sample. Subjects were 4,134 residents in selected sites in Japan. Diagnoses of mental disorders are based on the World Mental Health Survey Initiative Version of the World Health Organization Composite International Diagnostic Interview. Lifetime and 12-month prevalence of IED were 2.1% and 0.7%, respectively, whereas those of narrow IED were 1.2% and 0.6%, respectively. Male gender and young age were positively associated with an increased prevalence of IED. Mood and anxiety disorders as well as suicidal ideation were shown to be associated with IED in both genders. The overall association between anxiety disorders and IED was stronger in women than in men. Positive association of substance use problems with IED was also observed. Similar findings were observed between those psychosocial factors and narrow IED. These results suggest that people having those mixed complications might have a high suicidal risk. Further research using psychological measures for anger suppression will lead to more thorough understanding of the effects of IED on psychosocial comorbidity and suicidal risk.
Intermittent explosive disorder (IED) is characterized by discrete episodes of aggressive impulses that result in serious assaultive acts towards people or destruction of property, and is classified by the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) as one of the impulse-control disorders (American Psychiatric Association, 2000). This disorder causes major social or familial disruptions to patients, who are sometimes obliged to resign from their position or divorce because of their behavioral problems.
Formerly, few epidemiological studies had been conducted with regard to this disorder, and a lack of reliable clinical evidence regarding diagnosis, treatment, or prognosis was all too common (Olvera, 2002). This was partly due to the instability of the definition of IED, which has changed over the years, resulting in inconsistent findings on IED prevalence (Olvera, 2002). Some studies have assessed the prevalence of IED among psychiatric clinical-based populations (Coccaro et al., 1998, Lejoyeux et al., 1999 and Olvera, 2002). Prevalence estimated at approximately 25% was reported among patients with personality disorders with impulsive-aggressive behavior (Coccaro et al., 1998) or alcohol dependence (Lejoyeux et al., 1999), whereas prevalence among the general population of psychiatric outpatients was reported to be 3.1-6.5% (Olvera, 2002). It was also reported that 2% of all people admitted to a university hospital psychiatric service were diagnosed as IED, among whom 80% were males (Kaplan and Sadock, 1998). Coccaro (2000) indirectly estimated the community rate of IED at 0.9-1.8% based on the previous clinical and population-based studies.
Recently, however, several epidemiological studies of IED were conducted in general populations (Coccaro et al., 2004, Kawakami et al., 2005, Kessler et al., 2006, Ortega et al., 2008 and Fincham et al., 2009). Although the previous clinically based studies have reported a low prevalence of IED, the population-based prevalence of IED in recent reports has been shown to be higher than previously thought (Coccaro et al., 2004, Kessler et al., 2006 and Fincham et al., 2009). In addition, a high level of comorbidity is noted with mood, anxiety, and substance-related disorders (Kessler et al., 2006, Amara et al., 2007, Ortega et al., 2008 and Fincham et al., 2009). Since the former two categories are also strongly associated with substance-related disorders, it is important to evaluate the actual situation of the association between substance use and IED in a general population, so as to establish an effective IED treatment strategy.
Previous studies of IED took no account of the viewpoints of cross-cultural factors, in spite of the fact that behavioral problems related to impulsivity-control are likely to be strongly affected by cultural circumstances. In general, Japanese tend to more readily suppress their emotions, (especially overt anger) than Westerners or other Asian populations. This cultural proclivity may, to some extent, affect plain behavioral problems such as IED among Japanese.
The purpose of the present study is to evaluate both a lifetime and 12-month prevalence of IED as well as the comorbidity of mood, anxiety, and substance-related disorders with IED together with associations with behavioral problems caused by commonly used drugs, and suicidal ideation in a Japanese community sample based on data specific to Japan that were collected between 2002 and 2006 as part of the World Mental Health Surveys (WMH-J 2002-06 Survey) (WHO World Mental Health Survey Consortium, 2004).
