Research on intermittent explosive disorder (IED) has been hindered by vague and restrictive DSM-IV diagnostic criteria. Integrated research criteria have been developed for IED (IED-IR) that address the DSM-IV criteria’s shortcomings. The purpose of this study was to examine the convergent and discriminant validity of the IED-IR criteria set by comparing adults meeting these criteria (n = 56) to healthy controls (n = 56) and to individuals with an Axis I major mental disorder (n = 33) or an Axis II personality disorder (n = 22) diagnoses on measures of aggression (self-report and behavioral) and global functioning. IED-IR individuals demonstrated higher levels of aggression compared to the other three groups, and were rated as more impaired than the healthy control and Axis I individuals. Subgroup analyses showed that IED-IR subjects who did not meet DSM IED criteria did not differ from DSM IED subjects on self-report measures of aggressiveness or global functioning. Furthermore, the IED-IR subjects evidenced more behavioral aggression than their DSM-IED counterparts.
Aggression, defined as verbal or physical acts intended to cause emotional, psychological, or physical harm, is a major public health concern. Approximately 77 million adults have engaged in at least one serious act of physical aggression (Robbins and Reiger, 1991), and these numbers do not include acts of serious verbal aggression (e.g., screaming, threatening and cursing), which are even more ubiquitous (Newton et al., 2001). In the US alone, aggression costs hundreds of billions of dollars in annual healthcare expenditures, law enforcement expenses, and lost workplace productivity (US Department of Health and Human Services, 2000). The human costs of aggression are also substantial and include the intergenerational transmission of aggression from caregiver to child (Conger et al., 2003). The scope of aggression is sufficiently vast for the World Health Organization to proclaim violence as a leading worldwide public health problem (Krug et al., 2002).
Most definitions of aggression reflect the notion that aggression is multi-determined and can be expressed along a continuum of severity, from minor verbal assaults (yelling and cursing) to lethal physical aggression (Solari and Baldwin, 2002). Although aggressive acts across the spectrum of severity are quite common, the consensus of most clinicians and theorists is that some forms of aggression reflect psychopathology, whereas others merely constitute uncivil behavior (Stone, 1995). Furthermore, in some contexts, even severe acts of aggression are considered normal and adaptive (e.g., fighting back when physically attacked). Specific acts of aggression may be situational, but the tendency to behave aggressively represents a trait that begins early in life and continues through adulthood (Olweus, 1979). Identifying behavior sets that reflect psychopathological aggression has been a significant challenge to the field (Coccaro, 2003). However, the existence of valid formal diagnostic criteria sets to categorize pathological aggression would be of great benefit for both epidemiological and treatment research (Coccaro and Kavoussi, 1997 and Coccaro et al., 1998). In fact, diagnostic heterogeneity across subjects has been cited as one reason that effect sizes for anger/aggression treatments are smaller than those for depressive and anxiety disorders (DiGiuseppe and Tafrate, 2003).
Intermittent explosive disorder (IED) is the sole Diagnostic and Statistical Manual-4th Edition (DSM-IV-TR; American Psychiatric Association, 2000) psychiatric diagnostic category for which recurrent acts of aggression are a cardinal symptom (Table 1). Unfortunately, there are several significant limitations and ambiguities to this diagnostic entity. For example, DSM-IV IED sets no minimum requirement for how frequently the aggressive behaviors must occur, the time period demarketing the occurrence of these behaviors, or the severity of the behaviors that can be included (Coccaro, 2003). Likewise, despite the label “Intermittent Explosive Disorder,” the DSM-IV does not explicitly require that the aggressive behavior be “impulsive” or “explosive” in nature. Volitional, well-planned, and goal-directed violence arguably reflects social deviance, sociopathy, or criminal behavior rather than pathological impulsive aggression, and thus individuals who exhibit predominately non-impulsive forms of aggression should not be “captured” by the criteria set.
