Background. Impulsiveness, hostility and aggressiveness are traits associated with suicidal behavior, but also with borderline personality disorder (BPD). The presence of large numbers of BPD subjects in past attempter samples may distort the relative importance of each of these traits to predicting suicidal behavior, and lead to prospective, biological and genetic models that systematically misclassify certain subpopulations of suicidal individuals.
Method. Two hundred and seventy-five subjects with major depressive disorder (MDD), including 87 with co-morbid BPD (69 past suicide attempters, 18 non-attempters) and 188 without BPD (76 attempters, 112 non-attempters) completed standard impulsiveness, hostility and aggressiveness ratings. Differences between past suicide attempters and non-attempters were examined with the sample stratified by BPD status.
Results. As expected, BPD subjects scored significantly higher than non-BPD subjects on all three trait measures. Stratifying by BPD status, however, eliminated attempter/non-attempter differences in impulsiveness and hostility in both patient subgroups. Past suicide attempters in each of the two subgroups of patients were only distinguished by higher levels of aggressiveness.
Conclusions. Once BPD is accounted for, a history of aggressive behavior appears to be the distinguishing trait characteristic of suicide attempters with major depression, rather than global personality dimensions such as impulsiveness or hostility. Aggressiveness, and not these related traits, may be the ideal target for behavioral, genetic and biological research on suicidal behavior, as well as for the clinical assessment of suicide risk.