The Role of Impulsive Aggression in a Cohort of Suicide Attempters

Research Objective: This study attempts to understand the role of impulsive aggression in a group of suicide attempters. The study hypothesized that a greater proportion of suicide attempters would meet criteria as impulsive aggressive than would be found among suicide ideators and unintentionally injured controls. The study further hypothesized that levels of impulsive aggression among all study participants would remain stable across time. Methods: Three groups of patients (n = 291) were recruited, with suicide attempters as the experimental group and suicide ideators and traumatic injury patients as control groups. Subjects were evaluated for the presence of impulsivity and aggression during initial treatment for suicidality or unintentional injury and again three months later. Two hundred one of the initial recruits also completed a follow-up assessment. Using a definition of impulsive aggression previously developed by Skodol (2002), study patients identified as "impulsive aggressive" needed to meet three criteria: the presence of significant impulsivity a measured by the Barratt Impulsivity Scale (Barratt, 1994), and significant aggression, measured using two subscales (irritability and assaultiveness) from the Buss-Durkee Hostility Inventory (Buss&Durkee, 1956). Chi-square analyses, one-way ANOVAs, and interclass correlation coefficients were utilized to compare groups, with post hoc tests used as warranted. Covariates that are known to impact impulsivity and aggression (i.e., age, race, gender, depression, borderline personality disorder, and alcohol use/abuse) were controlled. Results: Before controlling for clinical differences between groups (e.g., levels of depression, alcohol use/abuse), chi-square analysis revealed significant differences in the number of impulsive aggressive individuals by group. A post hoc analysis suggested that the percentage of impulsive aggressive individuals was significantly higher among suicide ideators than among traumatic injury patients However, when covarying for age, gender, race, borderline personality disorder, major depressive disorder, and alcohol abuse, no differences were found in the level of impulsivity, irritability, or assaultiveness between groups. There was good consistency in the proportions of individuals by group who maintained their baseline level of impulsivity, irritability, and assaultiveness at follow-up, suggesting that these characteristics function in many individuals as a trait, rather than a state. In an attempt to corroborate the validity of this study's operationalized definition of impulsive aggression, external items that assessed these tendencies were identified and analyses were performed to see if participants who endorsed impulsive aggressive behavior also endorsed these external variables. There was not a good match between groups of individuals who were classified as impulsive aggressive using the traditional BIS-11/BDHI criteria and selected external variables. Conclusions: Findings from this research study do not support an association between impulsive aggression and suicidal behaviors.