I got the information below from the National Institute of Mental Health Web site.
Note: Some of these things may not apply to everyone! I just think NIMH had the best description I am in no way endorsing any certain website, just putting some useful information out there!
What is Borderline Personality Disorder?
Borderline Personality Disorder is a serious mental illness marked by unstable moods, behavior, and relationships. In 1980, the Diagnostic and Statistical Manual for Mental Disorders, Third Edition (DSM-III) listed Borderline Personality Disorder as a diagnosable illness for the first time. Most psychiatrists and other mental health professionals use the DSM to diagnose mental illnesses.
Because some people with severe borderline personality disorder have brief psychotic episodes, experts originally thought of this illness as atypical, or borderline, versions of other mental disorders.1 While mental health experts now generally agree that the name “borderline personality disorder” is misleading, a more accurate term does not exist yet.
Most people who have borderline personality disorder suffer from:
Problems with regulating emotions and thoughts
Impulsive and reckless behavior
Unstable relationships with other people.
People with this disorder also have high rates of co-occurring disorders, such as depression, anxiety disorders, substance abuse, and eating disorders, along with self-harm, suicidal behaviors, and completed suicides.
According to data from a subsample of participants in a national survey on mental disorders, about 1.6 percent of adults in the United States have borderline personality disorder in a given year.2
Borderline personality disorder is often viewed as difficult to treat. However, recent research shows that borderline personality disorder can be treated effectively, and that many people with this illness improve over time.1,3,4
What are the symptoms of borderline personality disorder?
According to the DSM, Fourth Edition, Text Revision (DSM-IV-TR), to be diagnosed with borderline personality disorder, a person must show an enduring pattern of behavior that includes at least five of the following symptoms:
Extreme reactions—including panic, depression, rage, or frantic actions—to abandonment, whether real or perceived
A pattern of intense and stormy relationships with family, friends, and loved ones, often veering from extreme closeness and love (idealization) to extreme dislike or anger (devaluation)
Distorted and unstable self-image or sense of self, which can result in sudden changes in feelings, opinions, values, or plans and goals for the future (such as school or career choices)
Impulsive and often dangerous behaviors, such as spending sprees, unsafe sex, substance abuse, reckless driving, and binge eating
Recurring suicidal behaviors or threats or self-harming behavior, such as cutting
Intense and highly changeable moods, with each episode lasting from a few hours to a few days
Chronic feelings of emptiness and/or boredom
Inappropriate, intense anger or problems controlling anger
Having stress-related paranoid thoughts or severe dissociative symptoms, such as feeling cut off from oneself, observing oneself from outside the body, or losing touch with reality.
Seemingly mundane events may trigger symptoms. For example, people with borderline personality disorder may feel angry and distressed over minor separations—such as vacations, business trips, or sudden changes of plans—from people to whom they feel close. Studies show that people with this disorder may see anger in an emotionally neutral face5 and have a stronger reaction to words with negative meanings than people who do not have the disorder.
Source: National Institute of Mental Health Web site.