Borderline personality disorder (BPD) is a mental health condition that is caused by a combination of factors. These factors include:

• Genetics: Genes inherited from parents may make a person more vulnerable to developing BPD, as there is evidence that the condition can run in families.

• Brain chemicals: Many people with BPD have something wrong with the neurotransmitters in their brain, particularly serotonin. Altered levels of serotonin have been linked to depression, aggression, and difficulty controlling destructive urges.

• Brain development: Problems with certain parts of the brain, such as the hippocampus and the orbitofrontal cortex, may contribute to symptoms of BPD. These parts of the brain are responsible for mood regulation, behavior, and self-control, and their development is affected by early upbringing.

• Environmental factors: A number of environmental factors seem to be common among people with BPD, including being a victim of emotional, physical, or sexual abuse, being exposed to long-term fear or distress as a child, being neglected by one or both parents, and growing up with another family member who had a serious mental illness or substance use disorder.

Its important to note that not everyone who experiences these factors will develop BPD, and not everyone with BPD has experienced all of these factors. The severity, frequency, and duration of symptoms are unique to each person.