What are the borders of borderline personality disorder?

It is argued that the usefulness of borderline personality disorder in clinical and research practice is largely because the borders of the diagnosis are so flexible. The diagnosis overlaps with other personality disorders, disturbances of mood and intermittent abnormal behavior. As almost all behavior likely to lead to consultation with mental health professionals is included among the elements of personality disorder, it is not surprising that it is almost the most common condition seen by specialists in the field. An attempt is made to define the borders of the condition in this review. It is concluded that these are so far-reaching that they negate the notion that borderline conditions are personality disorders. It is argued that the borderline state is a coaxial diagnosis of personality and mental state disorder and to continue to describe the concept as a personality disorder is wrong and misleading.