The biology of impulsivity and suicidality

Abnormalities of serotonergic and noradrenergic functioning have been assoc iated with aggressive impulsivity, self-injurious behavior, and suicidal be havior. The role of dopamine and gamma-aminobutyric acid in human studies o f these behaviors requires additional investigation. Most studies suggest t hat impulsive aggression is related to lower serotonergic activity, perhaps at the level of the amygdala or orbital prefrontal cortex. Some studies de monstrate that increasing norepinephrine correlates with more aggression. S elf-injurious behavior also seems to be mediated by the neurotransmitter sy stems previously mentioned. For example, lower levels of serotonin and abno rmalities in the dopaminergic system are related to self-injurious behavior in patients with borderline personality disorder or depression. Self-injur ious behavior severity also seems to be influenced by neglect (severe isola tion during rearing). Animal studies suggest that increasing the amount of isolation and an earlier onset of isolation increases the severity of self- injurious behavior. Suicidal behaviors and lethality of suicide attempts ca n also be linked to the abnormalities in neurotransmitter systems similar t o those found in impulsive aggression or self-injurious behaviors, namely l owered serotonergic transmission and enhanced dopaminergic and noradrenergi c function. Understanding the biologic triggers of impulsive aggression or self-injurious behaviors may eventually help early prediction and preventio n of suicidal behaviors. Additional studies of live subjects and postmortem brains will assist in clarifying the neurobiology of suicidal behaviors th at are common to many disorders but clinically are relevant to borderline p ersonality disorder.