A new study published in the American Journal of Psychiatry has given some insight into the biological underpinnings of BPD.  For those who do not know what BPD is, I'll go over it quickly.  BPD is characterized by "a pervasive pattern of instability of interpersonal realationships, self-image, and affects, and marked impulsivity that begins by early adulthood and is present in a variety of contexts (APA, 2000, pp. 706)*".  BPD can have difficult diagnostic considerations since some of the aspects of BPD also fit with other disorders such as schizotypal personality disorder and it often is co-morbid with another personality disorder.

For those who are curious, the DSM-IV-TR diagnostic criteria for BPD are as follows:

A pervasive pattern of instability of interpersonal relationships, self-image, and affects, and marked impuslivity beginning by early adulthood and present in a variety of contexts, as indicated by five (or more) of the follow:

(1)  frantic efforts to avoid real or imagined abandonment.  NOTE: Do not include suicidal of self-mutilating behavior covered in Criterion 5.

(2)  a pattern of unstable and intense interpersonal relationships characterized by alternating between extremes of idealization and devaluation.

(3)  identity disturbance: markedly and persistently unstable self-image or sense of self

(4)  impulsivity in at least two areas that are potentially self-damaging (e.g., spending, sex, substance abuse, reckless driving, binge eating).  NOTE: Do not include suicidal or self-mutilating behavior covered in Criterion 5.

(5)  recurrent suicidal behavior, gestures, or threats, or self-mutilating behavior

(6)  affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability, or anxiety usually lasting a few hours and only rarely more than a few days)

(7)  chronic feelings of emptiness

(8)  inappropriate, intense anger or difficulty controlling anger (e.g., frequent displays of temper, constant anger, recurrent physcial fights).

(9)  transient, stress-related paranoid ideation or severe dissociative symptoms.

Okay, still with me?  Good.  Within the criteria a pattern of inability for inhibition of emotions, especially negative ones, seems to be present.  This is explained in the paper by Silbersweig et al. as a dysfunction in key areas of the prefrontal cortex.

The prefrontal cortex, along with other tasks, performs what is called the "executive function" - it filters, so to speak the signals from other areas of the brain, especially the limbic system (the seat of our emotions).  Silbersweig et al found decreased activity in a portion of the PFC called the ventromedial prefrontal cortex.  This area has been associated with inhibition of emotional responses in particular situations that would normally elicit an emotional response.  In a group of BPD patients, the researchers found disinhibition in that area when compared to healthy controls.  They also say increased activity in limbic areas, especially the amygdala - the limbic structure associated with fear and aggression.

This study is important as it provides specific anatomical areas to focus on for further study and may lead to more effective treatments for those who suffer from this disorder.

* American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text Revision).  Washington, D.C.: American Psychiatric Association