Impulsivity and aggressiveness are trait dispositions associated with the vulnerability to suicidal behavior across diagnoses. They are associated with structural and functional abnormalities in brain networks involved in regulation of mood, impulse and behavior. They are also core characteristics of borderline personality disorder (BPD), a disorder defined, in part, by recurrent suicidal behavior. We assessed the relationships between personality traits, brain structure and lethality of suicide attempts in 51 BPD attempters using multiple regression analyses on structural MRI data. BPD was diagnosed by the Diagnostic Interview for Borderline Patients-revised, impulsivity by the Barratt Impulsiveness Scale (BIS), aggression by the Brown–Goodwin Lifetime History of Aggression (LHA), and high lethality by a score of 4 or more on the Lethality Rating Scale (LRS). Sixteen High Lethality attempters were compared to 35 Low Lethality attempters, with no significant differences noted in gender, co-morbidity, childhood abuse, BIS or LHA scores. Degree of medical lethality (LRS) was negatively related to gray matter volumes across multiple fronto-temporal–limbic regions. Effects of impulsivity and aggression on gray matter volumes discriminated High from Low Lethality attempters and differed markedly within lethality groups. Lethality of suicide attempts in BPD may be related to the mediation of these personality traits by specific neural networks.
Personality traits such as impulsivity and aggressiveness are associated with suicidal behavior across diagnoses. In a stress–diathesis model of suicide, they represent vulnerable temperaments, and predispositions to impulsive and aggressive behavior in response to specific trigger events (for review, see Mann et al., 1999 and Mann, 2003). Trait dispositions such as impulsivity and aggressiveness may be heritable (e.g., as endophenotypes), or acquired in the course of development (e.g., through childhood abuse). In neuroimaging studies, they have been associated with variations in the structure and function of brain networks that regulate mood, impulse and behavior. At times of emotional stress, dysfunction in these neural networks may result in interference with executive cognitive functions, such as response inhibition, conflict resolution, and recall of episodic memory (for review, see Fertuck et al., 2006). As a result, problem solving and adaptive coping are impaired, increasing the likelihood of impulsive or aggressive behavior. We study the relationship between personality characteristics, brain function and suicidal behavior in the context of borderline personality disorder (BPD), a personality disorder defined, in part, by recurrent suicidal behavior, impulsivity and aggression. With a suicide rate of 3–10% and a community prevalence estimated at 1% of the population, BPD is a clinically relevant model for the study of suicide (Swartz et al., 1990).
There is a paucity of neuroimaging studies in BPD subjects ascertained specifically for suicidal behavior. In a voxel-based morphometry study (VBM) comparing BPD suicide attempters with BPD non-attempters, we recently reported specific structural differences in BPD subjects associated with suicidal behavior, and differences between High Lethality and Low Lethality suicide attempters (Soloff et al., 2012). BPD attempters had diminished gray matter concentrations in left insular cortex compared with BPD non-attempters. High Lethality attempters had diminished gray matter compared with Low Lethality attempters in an extensive fronto-limbic network including the following regions: right middle-inferior orbital frontal cortex, right middle-superior temporal cortex, right insular cortex, left fusiform gyrus, left lingual gyrus, and right parahippocampal gyrus. These areas are broadly involved in emotion regulation, behavioral control, and adaptive responding to social situations. Suicide researchers have long maintained that suicide attempters and completers represent separate but overlapping populations, with differing clinical characteristics (Maris et al., 2000). High Lethality attempters share many clinical characteristics with patients who complete suicide and may share neurobiological vulnerabilities related to high-risk personality traits such as impulsivity and aggressiveness.
To assess the relationships between personality traits, brain structure, and suicidal behavior, we used a multiple regression analysis of VBM data in High and Low Lethality BPD attempters to map the relationships between impulsivity, aggression and gray matter in key brain structures.
There were 51 BPD attempters subdivided as follows: 16 High Lethality (5 male, 11 female) and 35 Low Lethality attempters (5 male, 30 female), with no significant group differences by gender, race or socioeconomic status (Table 1). The mean (S.D.) age of the sample was 30.1 (8.1) years with a range of 18–47 years. High Lethality attempters were significantly older (36.1 (9.2) years) than Low Lethality attempters (27.4 (5.9) years, t=3.47, d.f.=20.95, P=0.002). The two groups did not differ significantly in proportion of subjects with current or lifetime co-morbid Axis I disorders, including the following: major depressive disorder (MDD), alcohol abuse or dependence, other drug abuse or dependence, any anxiety disorder, or post-traumatic stress disorder. The most frequent current co-morbid diagnosis, MDD, was found in 12 High Lethality (75%) and 21 Low Lethality attempters (60%), with no significant difference between groups in severity of depressed mood (HamD) at the time of the scan ( Table 1). Similarly, there were no significant differences between groups for BIS and LHA scores, and no significant correlation between these scores across all attempters. A history of childhood abuse was found in 7 High Lethality (43.8%) and 13 Low Lethality attempters (37.1%), with no significant difference between groups. Of the 51 subjects, 21 (41.5%) were taking psychoactive medication at the time of the scan, with no proportional difference between High and Low Lethality subjects.
