The short answer is that no definitive set of causes has been identified that results in BPD.

There are, however, a number of factors that seem to play a role in the development of BPD.

As with many psychobiological disorders there are those who believe that biology plays the larger, if not the only, role and there are others who believe that psychology plays a critical role. BPD is not exempt from this debate.

For BPD there are two possible causative agents: a biological one and a psychotraumatic one. The biological agent could be a gene or set of genes which predisposes a person to BPD; it could also be a physical agent that directly leads to a neurotransmitter imbalance. The probable psychological cause is early childhood psychotrauma. Over 75% of people diagnosed with BPD report credible psychotrauma during childhood.

Thus far no specific gene(s) have been isolated that correlate with BPD. Some research shows that families of people who have BPD are more likely to have mood disorders. Neurotransmitter imbalances, particularly catecholamine imbalances, are thought to be correlated with BPD. What causes this possible imbalance is unknown. For more information about the research on the biological causes of BPD see my article on my theory of BPD.

The case for psychotrauma's role in BPD is a bit clearer. A very high percentage of people with BPD have a history of childhood trauma. A researcher by the name of Perry has shown that early childhood trauma effects the way the brain develops causing among other things a chronic "flight or fight" response in affected individuals. The symptoms of BPD overlap with this pattern of behavior. Therefore it seems reasonable to infer that early psychotrauma can lead to a pattern of behavior that is often diagnosed as BPD.

Psychotrauma can occur at many levels of intensity and duration. Nor does it have to occur at only the highest level of intensity such as physical or sexual abuse for it to affect a child. Chronic exposure to lower levels of psychotrauma can also have lasting effects on personality development. The source of the psychotrauma is also an important factor (a trusted person versus an act of nature).

Of course, more research is needed to determine whether or to what degree psychotrauma plays a role in the development of BPD. The same is true of biological research into genetic or other biological agents that may also play a role in the development of BPD.

My own model of BPD (view model), based on over twenty years of clinical work, is called the Equifinality Model of BPD. Simply described it says that BPD is really two, not one, disorders. People who have a history of psychotrauma prior to age 16 and who meet DSM-IV criteria for BPD have what I call type I BPD better described as Psychotraumatized Type. People who do NOT have a psychotraumatic history but who meet DSM-IV criteria for BPD and do NOT meet DSM-IV criteria for bi-polar disorder have type II BPD better described as Cyclothymic Type. In my experience less than 25% of people diagnosed with BPD are type II, cyclothymic. The more severe the symptoms of BPD (such as cutting) are the more likely it is that a history of childhood psychotrauma exists.

Some professionals tend to give people with BPD multiple diagnoses which simply reflect what I have just described. It is not uncommon for them to have substance abuse, PTSD, eating disorder, ADHD, major depression or bi-polar disorder as co-occurring conditions. Many of the symptoms of these conditions overlap with those of BPD making accurate diagnosis of co-occurring conditions very difficult and potentially counterproductive by burdening the individual with many diagnoses where only one may do.

Political considerations also play a role in deciding whether BPD is more biologically caused than psychotraumatically caused. Because people assume that a biological cause eliminates personal responsibility in ways that psychological causes do not their preference is to insist that BPD is a biological disorder. This may relieve some people of guilt feelings or encourage insurance companies to pay for care but may do little to help those who suffer from the disorder especially if psychotrauma does play a significant role. In actual fact we do not have as much control over the psychological influences in our life as we like to think we do. Furthermore, everything that is psychological acts biologically on us. After all we are made up of biological matter and because of this everything we do is biologically executed by our brain and body. When we say that something is psychological we mean that it is informational and experiential as opposed to viral, bacterial or molecular. The simple analogy is the difference between software and the computer that operates it. A computer may malfunction because its software is full of bugs or because its chips are defective or for both reasons. Our psychology is our software and our biological structure is our hardware; the two are not independent of each other but interact and alter one another continuously.

People with BPD do not have a biological disorder and they do not have a psychological disorder. They have a psychobiological disorder whose origins are only beginning to be better understood.

For more information or to dialog about BPD contact me at santoro@slshealth.com.