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Borderline personality disorder

Unstable emotions, thoughts and behaviour are symptoms that can be associated with borderline personality disorder, a mental health condition that can have distressing effects on the person's life.

What is borderline personality disorder?

A personality disorder is a condition in which a person's feelings, thoughts, perceptions and behaviour are significantly different from those of an average person. The World Health Organisation (WHO) classifies personality disorders into ten different types, separated into three clusters. Borderline personality disorder – also known as unstable personality disorder in Europe – is one of the 'Cluster B personality disorders', where a person struggles in regulating their feelings and thoughts, often changing between positive and negative views of others that can lead to dramatic, unpredictable and even disturbing behaviour. A person with borderline personality disorder will have strong emotions, feelings and mood swings, may feel unable to cope easily and may often feel stressed.

The term 'borderline' personality disorder is inaccurate. It comes from a previously held belief that someone with the condition was bordering between two different conditions: neurosis (when a person is under mental stress but still knows the difference between reality and perception) and psychosis (where a person cannot determine the difference between reality and perception – a psychotic person may have delusions and hallucinations).

Health-care professionals now consider borderline personality disorder (BPD) to be a condition that has a significant impact on a person's moods and ability to interact with others.

How does borderline personality disorder develop?

BPD is a common personality disorder that usually emerges in adolescence but is not normally diagnosed until adulthood. About 75% of those diagnosed with BPD are women, and about one in 100 people from the general population has the disorder. The causes for BPD are unclear, but experts believe that a combination of factors is likely to be responsible and these include:

  • Neurotransmitters: There is limited evidence that indicates people with BPD have altered functioning of neurotransmitters; one of them is serotonin, which has been linked to depression, aggression and difficulty in managing destructive urges, and two others are dopamine and noradrenaline, both associated with emotional instability.
  • Neurobiology: Research has shown that parts of the brains of people with BPD may have unusual levels of activity or may be smaller than normal, in particular the amygdala (the region that helps regulate emotions), the hippocampus (which helps regulate self-control and behaviour) and the orbitofrontal cortex (which is involved in decision making and planning); early childhood upbringing can have an impact on the development of these areas of the brain.
  • Environmental factors: Traumatic childhood events have occurred in an estimated 8 out of 10 people with BPD – these include parental neglect, being exposed to chronic fear or distress as a child, growing up with a family member with a mental health problem (such as alcohol or drug misuse or bipolar disorder), and emotional, physical or sexual abuse.
  • Genetic: Inheriting certain genes from a parent could make someone more likely to develop BPD, however scientists have not found evidence of a gene linked to BPD and there has been limited research in this area.

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