Borderline personality disorder (BPD) is part of a group of mental illnesses known as personality disorders. It is a condition characterized by long term patterns of unstable emotions. These emotions often result in impulsive actions and an inability to form stable relationships causing significant problems for the sufferer. It results in a person being unable to function in a stable and effective manner. Assessment of BPD based on all the symptomatic criteria can only be made once a person is an adolescent or an adult.
Historically, the symptoms associated with BPD include both mood problems, known as neuroses and distortions of reality, known as psychoses. For this reason it was thought to be on the borderline between mood problems and schizophrenia. Today, despite having symptoms that fall between these two illnesses, BPD is considered to be closely related to other personality disorders when looking at how these illnesses develop within families. It occurs equally in men and women and affects nearly 6% of all adults over the course of their life.