Comorbidity of personality disorder with intermittent explosive disorder

There is ambiguity in how recurrent anger and aggression are accounted for by psychiatric nosology. One area of uncertainty is the extent to which Intermittent Explosive Disorder (IED) overlaps with and is distinct from Personality Disorder (PD). Accordingly, we conducted a study of individuals with IED and PD in order to understand the nature of comorbidity relationships seen across these two areas of psychopathology. One-thousand-five-hundred-twenty-one adults were studied (441 Healthy Controls (HC), 430 Psychiatric Controls (PC), and 650 IED subjects) and assessed for DSM-5 psychiatric disorders, life history of aggressive behavior, trait aggression, state and trait anger reactivity, and impulsivity. While nearly half of IED study participants had a comorbid PD diagnosis, nearly half with a Cluster B PD, almost as many had other personality disorders. IED predicted anger symptoms and history of aggressive behavior above and beyond a PD diagnosis. Comorbidity between IED and either Antisocial (AsPD) or Borderline (BPD) PD was associated with the highest levels of aggressive behavior. However, having IED comorbid with either AsPD and/or BPD PD was not associated with higher levels of impulsivity. Underlying personality traits related to anger, affect, and social behavior, but not identity disturbance, contribute to the shared symptom profile of IED and PD. IED is usually comorbid with PD, but does not have a unique relationship with any single PD. When comorbid with PD, a diagnosis of IED predicts more severe anger and aggression, but not necessarily increased impulsivity. These results suggest that IED and PD diagnoses retain clinical utility when made in cases meeting criteria for both.