Suicidal subtypes, stress responsivity and impulsive aggression.

While prominent models of suicidal behavior emphasize the hypothalamic- pituitary-adrenal (HPA) axis dysregulation, studies examining its role have yielded contradictory results. One possible explanation is that suicide attempters are a heterogeneous group and HPA axis dysregulation plays a more important role only in a subset of suicidal individuals. HPA axis dysregulation also plays a role in impulsivity and aggression. We hypothesize subgroups of attempters, based on levels of impulsivity and aggression, will differ in HPA axis dysregulation. We examined baseline cortisol, total cortisol output, and cortisol reactivity in mood disordered suicide attempters (N = 35) and non-attempters (N = 37) during the Trier Social Stress Test. Suicide attempters were divided into four subgroups: low aggression/low impulsivity, high aggression/low impulsivity, low aggression/high impulsivity, and high aggression/high impulsivity. As hypothesized, attempters and non-attempters did not differ in any cortisol measures while stress response differed based on impulsivity/aggression levels in suicide attempters, and when compared to non-attempters. Specifically, attempters with high impulsive aggression had a more pronounced cortisol response compared with other groups. This is the first study to examine the relationship between cortisol response and suicidal behavior in impulsive aggressive subgroups of attempters. These findings may help to identify a stress responsive suicidal subtype of individuals.