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Borderline personality disorder

There is no single cause of borderline personality disorder (BPD). It is caused by a combination of factors.


There is no evidence for a gene for BPD. But genes you inherit may make you more vulnerable to developing BPD.

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

It has been identified that in many people with BPD, 3 parts of the brain were different than others. They 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 early upbringing.

These parts of your brain are also thought to have a role in mood regulation. 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 one or both parents
  • growing up with a family member who had a mental health condition. For example, bipolar disorder or a substance use problem

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 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.

page last reviewed: 23/09/2018
next review due: 23/09/2021

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