Although the cause of BPD is unknown, both environmental and genetic factors are thought to play a role in predisposing patients to BPD symptoms and traits. Studies show that many, but not all individuals with BPD report a history of abuse, neglect, or separation as young children.8 Forty to 71 percent of BPD patients report having been sexually abused, usually by a non-caregiver.9 Researchers believe that BPD results from a combination of individual vulnerability to environmental stress, neglect or abuse as young children, and a series of events that trigger the onset of the disorder as young adults. Adults with BPD are also considerably more likely to be the victim of violence, including rape and other crimes. This may result from both harmful environments as well as impulsivity and poor judgment in choosing partners and lifestyles.

NIMH-funded neuroscience research is revealing brain mechanisms underlying the impulsivity, mood instability, aggression, anger, and negative emotion seen in BPD. Studies suggest that people predisposed to impulsive aggression have impaired regulation of the neural circuits that modulate emotion.10 The amygdala, a small almond-shaped structure deep inside the brain, is an important component of the circuit that regulates negative emotion. In response to signals from other brain centers indicating a perceived threat, it marshals fear and arousal. This might be more pronounced under the influence of drugs like alcohol, or stress. Areas in the front of the brain (pre-frontal area) act to dampen the activity of this circuit. Recent brain imaging studies show that individual differences in the ability to activate regions of the prefrontal cerebral cortex thought to be involved in inhibitory activity predict the ability to suppress negative emotion.11

Serotonin, norepinephrine and acetylcholine are among the chemical messengers in these circuits that play a role in the regulation of emotions, including sadness, anger, anxiety, and irritability. Drugs that enhance brain serotonin function may improve emotional symptoms in BPD. Likewise, mood-stabilizing drugs that are known to enhance the activity of GABA, the brain's major inhibitory neurotransmitter, may help people who experience BPD-like mood swings. Such brain-based vulnerabilities can be managed with help from behavioral interventions and medications, much like people manage susceptibility to diabetes or high blood pressure.7

References:

7Siever LJ, Koenigsberg HW. The frustrating no-mans-land of borderline personality disorder. Cerebrum, The Dana Forum on Brain Science, 2000; 2(4).

8Zanarini MC, Frankenburg. Pathways to the development of borderline personality disorder. Journal of Personality Disorders, 1997; 11(1): 93-104.

9Zanarini MC. Childhood experiences associated with the development of borderline personality disorder. Psychiatric Clinics of North America, 2000; 23(1): 89-101.

10Davidson RJ, Jackson DC, Kalin NH. Emotion, plasticity, context and regulation: perspectives from affective neuroscience. Psychological Bulletin, 2000; 126(6): 873-89.

11Davidson RJ, Putnam KM, Larson CL. Dysfunction in the neural circuitry of emotion regulation - a possible prelude to violence. Science, 2000; 289(5479): 591-4.

NIH 2001