Borderline Personality Disorder is identified in Cluster B of Axis II of the Multiaxial system. As all personality disorders, it is characterized as a pervasive and inflexible pattern of inner experiences and behavior that cause distress and certain impairment in a person’s life (DSM-IV-R).
Being a mental illness, BPD implies instability in moods, self-image, and behavior, as well as in interpersonal relationships. People suffering from BPD have a hard time regulating their emotions and often have to deal with their impaired sense of self-identity (Linehan M, 2006). Frequently, BPD involves intense outbursts of anger, depression and anxiety that can last for only hours, or a day (Zanarini MC, 1998).
There is a hypothesis that BPD is a trauma-related disorder or a variant of Post Traumatic Stress Disorder (PTSD). A research indicated that people with BPD had significantly higher rates of PTSD when compared to subjects suffering other Personality Disorders (25% versus 13.0%) (Golier J, 2003).
People with BPD have critically unstable patterns of social relationships. This includes intense attachments and attitudes towards friends, family or loved ones that can change rapidly. Strong feelings of love and admiration can be suddenly replaced by anger or dislike. These intense emotional reactions in daily life are out of proportion and often may cause conflicts. Also, people with BPD tend to be extremely sensitive to rejection and separation, reacting with distress, outbursts of anger, episodes of anxiety, depression, and feelings of helplessness, worthlessness, suicide threats and attempts (Golier J, 2003). In addition, subjects with BPD may be at a greater risk of exposure to new traumas, substance abuse and risky behaviors due to their instability and 
impulsivity (Golier J, 2003).
Research shows that BPD is affecting up to two percent of adults in the United Stated (approximately 5.8 to 8.7 million Americans, mostly young women) (Swartz M, 1990). Since self-harm is very common in borderline patients (cutting, burning, suicide attempts), up to nine percent of subjects suffering BPD ultimately kill themselves (Linehan M, 2006). Patients of BPD stand for about 20% of psychiatric hospitalizations (Zanarini MC, Frankenburg FR. Treatment histories of borderline inpatients. Comprehensive Psychiatry, in press).