Genetics. Some studies of twins and families suggest that personality disorders may be inherited.
Environmental factors. Many people with borderline personality disorder have a history of childhood abuse, neglect and separation from caregivers or loved ones.
Brain abnormalities. Some research has shown changes in certain areas of the brain involved in emotion regulation, impulsivity and aggression. In addition, certain brain chemicals that help regulate mood, such as serotonin, may not function properly.
Hereditary predisposition. You may be at a higher risk if a close family member — a mother, father or sibling — has the disorder.
Childhood abuse. Many people with the disorder report being sexually or physically abused during childhood.
Neglect. Some people with the disorder describe severe deprivation, neglect and abandonment during childhood.