The interrelationship among aggression, impulsivity, auditory P300 and executive function in a clinical population

The heterogeneous nature of aggression can complicate the examination and interpretation of the causes and correlates of violent and aggressive behavior. The current archival study presents one characterization system for classifying chronic aggressive behavior. Personality, neuropsychological, and psychophysiological measures were employed to test the meaningfulness of this system, as well as evaluate a proposed biopsychosocial model of human aggression. Research hypotheses sensitive to aggression subtype were tested for lifetime history of aggression, impulsivity, executive function (composite executive measure index), and auditory P300 amplitude. The aggression model was composed of anger score and the aforementioned variables. Model analyses were performed on the total sample and two subgroups (by referral source). Subjects were 273 consecutive patients from 1997 to 2003 that were clinic-referred, self-referred, or court-referred to a university anger clinic for assessment due to problems with aggressive behavior, as well as 35 nonaggressive community controls. After written and verbal consent, all participants completed a test battery that included similar personality, neuropsychological and psychophysiological measures. Characterization of aggressive subtype was determined by at least two investigators and all DSM diagnoses were made by the same licensed clinical neuropsychologist. Results by aggressive subtype indicate that Impulsive (IA), Premeditated (PM) and Secondary (SEC; secondary to the effects of a psychiatric or medical disorder) aggressors have greater lifetime histories of aggression than Controls. IA and PM score higher on Impulsivity than Controls; and lastly, SEC exhibit a lower executive index than IA, PM, and Controls. Contrary to expectations, there were no differences among the groups on P300 amplitude. Examination of the aggression model in the total sample, clinic-referred sample, and self-referred sample revealed support for a link between impulsivity and aggression, partially mediated by anger, and in one case (self), totally mediated by anger. Also, in the clinic-referred sample, a relationship between executive function and aggression was found to be mediated by impulsivity. There were no significant relationships between auditory P300 and aggression in any of the three samples. Overall, the results provide support for aggressive subtype characterization (personality measures) and demonstrate the strong relationships among anger, impulsivity and aggression in a clinical population.