Since this is a condition that is diagnosed by the presence or absence of a group of symptoms rather than any one specific test our understanding continues to change. Some authors have suggested that there are several levels or types of Borderline Personality Disorder. People with milder BPD symptoms can be described as having Borderline traits. It is possible that various levels of BPD symptoms may have different causes.
Like most other mental illnesses, Borderline Personality Disorder (BPD) appears to have both a genetic risk factor and an environmental risk factor. Having a risk factor does not mean that you are going to develop the disorder but the more the risk factors the more the risk.
NIMH (National Institute of Mental Health reported some time back (2008,) that there appears to be a genetic risk factor for BPD. This study found that a particular mutation on chromosome nine created an increased risk for BPD. At some point in the human past the characteristics we think of Borderline traits may have been helpful in certain situations.
Experience has made any one research report linking a particular chromosome and a disorder highly suspect. It would be nice if this study were correct and we could do a simple test for BPD but with other disorders we find that it is not one gene or chromosome that creates mental illness. It is the influences of several or a combination of large numbers of the many possible genes that result in an increase risk.
In this study the contribution of genetics was 40%. Meaning that environment contributed the other 60% or put another way, your relationships and experiences increase the risk of developing BPD 150% as much as your genetics.
One factor seems to contribute a huge amount of this environmental risk.
Growing up in a non-affirming place with people who did not validate you, is a hugely important cause of many of the symptoms that make up BPD and Borderline Personality traits.
Many people with borderline traits report that their family was not supportive. Their caregivers were either absent or constantly frustrating.
Many people with BPD grew up in homes that did not create the feeling of being valued as a human being. People with BPD may have been neglected, abused or simply did not have their emotional needs met. They may have found that direct requests for things did not work and that the only way to get their needs met was too engage in behaviors that forced the family to notice them. In adult life there behaviors will be described as manipulative.
A borderline can be both clingy and distant, wanting a close intimate relationship but also fearful that to let someone get in close to them invites another abandonment.
People with BPD may associate any accomplishment with an increased risk of abandonment. They often quit school a week before finals or fail to show up for a job on the first day.
Borderlines may end up slipping in to a relationship with someone who has difficulty being close. Just like the co-dependent who keeps marrying the alcoholic trying to get it right, someone with BPD may continue to enter relationship with a partner who is unable to provide any warmth and closeness.
The classic expression of this feeling becomes “If I become fully me, will you stop loving me?” The recurring fear is that the significant person in their life will abandon them and they will fall apart without someone to support them.
One issue people with BPD may need to tackle is the inability to have and enjoy happiness or other positive feelings. If you came from an environment that said it was not ok to have or display feelings, it can be terrifying to allow yourself to feel happiness of any sort.
The person with PBD may feel empty, numb or bored without someone else in their life that provides for their needs. The theory here is that the more the person was let down by their support system, the less able they have been at becoming an independent person, the more likely they will be to develop borderline traits.
Those with BPD often come from homes where the caregivers themselves had poorly regulated emotional lives. Parents can and do frequently provide genetic risk factors, environmental factors and learned behavior that support he continuation of BPD.
Is seems likely that living with or around a caregiver with BPD is likely to alter the way in which someone handles emotion.
The take away from all this is that whatever the reason someone has BPD there are treatments available that can help manage, reduce or eliminate the symptoms of Borderline Personality Disorders.