Borderline personality disorder alters your self-concept, how you behave and how you relate to others.
The interpersonal relationships are usually in trouble. You often have a love-hate relationship with others. You may idealize someone one moment and then abruptly and dramatically shift to fury and hate over perceived slights or even minor misunderstandings. This is because people with the disorder have difficulty accepting things that are not that good — things are either black or white. For instance, in the eyes of a person with Borderline Personality Disorder, someone is either good or evil. And that same person may seem good one day and evil the next.
When you have Borderline Personality Disorder, you often have an insecure sense of who you are. That is, your self-image or sense of self often rapidly changes. You may view yourself as evil or bad, and sometimes may feel as if you don’t exist at all. An unstable self-image often leads to frequent changes in jobs, friendships, goals, values and gender identity.
Some signs and symptoms of borderline personality disorder can be:
Fear of being alone
Impulsive and risky behavior, such as risky driving, unsafe sex, gambling sprees or taking illicit drugs
Inappropriate anger, sometimes escalating into physical confrontations
Strong emotions that wax and wane frequently
Intense but short episodes of anxiety or depression
Suicidal behavior
Difficulty controlling emotions or impulses

Despite the fact that definitive data are lacking, it’s estimated that 1 percent to 3 percent of American adults have borderline personality disorder. As with other mental disorders, the causes of borderline personality disorder are complex. The name came out because of theories in the 1940s and 1950s that the disorder was on the border between neurosis and psychosis. But that view doesn’t reflect current thinking. The truth is, some advocacy groups have pressed for changing the description, such as calling it emotional regulation disorder.
Nevertheless, the cause of BPD is still yet to be uncovered, and there’s no known way to prevent it. Possible causes include:
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.
Environmental factors. Many people with borderline personality disorder have a history of childhood abuse, neglect and separation from caregivers or loved ones.
Genetics. Some studies of twins and families suggest that personality disorders may be inherited.
It is thought that a combination of these issues results in BPD.