Signs and symptoms of borderline personality disorder may include:

• Difficulty controlling emotions or impulses

• Frequent emotional ups and downs

• Impulsive actions

• Mood swings

• Stormy relationships

• Intense anger, possibly involving physical fights

• Casting others in terms of good or bad

• Feeling of emptiness inside

• Fear of being alone

Unlike the mood changes in disorders such as depression and bipolar disorder, which may last for weeks or months, the mood swings in BPD generally last just hours.

People affected with BPD are terrified of being alone, yet they push others away with their erratic behavior. They often get into repetitive, rather predictable crises often related to the fear of abandonment, while in reality their behaviors often lead to just that.

Common occurrences, such as a spouse being a few minutes late, may prompt sudden fury or despair. People with BPD are likely to believe this "abandonment" implies that their partners don't love them anymore or that they're "bad." When a loved one is perceived as uncaring, a person with BPD may react with extreme sarcasm, lingering bitterness or verbal abuse. These outbursts may be followed by feelings of guilt.

People with BPD may idolize a new lover and demand lots of time together. This switches quickly to devaluing that person and feeling that the person doesn't care enough or isn't dependable. As a result, relationships often are stormy and unstable.

Affected people may also experience sudden and dramatic shifts in their self-image, which can be expressed in a shift of their goals and values. They may quickly change their opinions and plans about their career, sexual identity and types of friends.

The term borderline comes from the thinking of psychiatrists in the 1940s and 1950s that the disorder bordered on and shared features of psychotic and neurotic disorders. But that view doesn't reflect current thinking.

Doctors don't know for sure what causes borderline personality disorder, but there are clues. Most likely, no single factor explains its development. Instead, it may be a combination of:

• Hereditary predisposition. You may be at a higher risk of BPD if a close family member — mother, father or sibling — has it.

• Childhood abuse. Some people with BPD may have been physically or sexually abused as children.

• Neglect. Some people with BPD describe severe deprivation, neglect and abandonment during childhood.

• Neurologic injury in early childhood. There appears to be a high prevalence of childhood head injuries in people with BPD.