There is no one single cause of borderline personality disorder (BPD). It is caused by a combination of things.
Genetics
There is no evidence for a gene for BPD. But genes you inherit may make you more vulnerable to developing it.
Brain chemicals
Neurotransmitters may be involved in the development of BPD. But more research is needed to know how much of a factor they play.
Brain development
Research has shown that in many people with BPD, 3 parts of the brain were were either smaller than expected or had unusual levels of activity.
These are the:
- amygdala – plays an important role in regulating emotions
- hippocampus – helps regulate behaviour and self-control
- orbitofrontal cortex – helps planning and decision making
Problems with these parts of the brain may contribute to symptoms of BPD.
The development of these parts of the brain is affected by your experiences during childhood.
These parts of your brain are also thought to have a role in regulating your mood. They may account for some of the problems people with BPD have in close relationships.
Environmental factors
Some environmental factors seem to be common among people with BPD.
These include:
- being a victim of emotional, physical or sexual abuse
- being exposed to chronic fear or distress as a child
- being neglected by 1 or both parents
- growing up with a family member who had a mental health condition - for example, bipolar disorder, or a problem with substance use
Your relationship with your family has a strong influence on how you come to see the world. It influences what you believe about other people.
Unresolved childhood fear, anger and distress can lead to certain thinking patterns, such as:
- idealising others
- expecting others to be a parent to you
- expecting other people to bully you
- behaving as if other people are adults and you're not
Content supplied by the NHS and adapted for Ireland by the HSE