Borderline personality disorder can be a difficult diagnosis because of similarities to other conditions, particularly mood disorders. It is a common presentation in both psychiatric and general practice, with accurately diagnosed cases seen in 10% of psychiatric outpatients, 20% of psychiatric inpatients1,2 and 6% of family medicine patients.3 These values are higher than would be expected given a prevalence of about 1% in the general population.4 Women account for 70% of patients with this disorder in clinical settings,5and the most common age at first presentation is in late adolescence.6 Unfortunately, a large proportion of patients with the disorder are not identified in practice.3
Patients with borderline personality disorder are frequently encountered in the emergency department, where they present following threatened suicide or a suicide attempt. More than 500 000 such visits to emergency departments occur each year in the United States.7 The incidence of suicide attempts among patients with borderline personality disorder is highest among those in their twenties, but mortality peaks in the thirties, with a 10% lifetime rate of completed suicide.8
Retrospective studies have shown that symptoms resolve over time, with 75% of patients at 15-year follow-up and 92% of patients at 27-year follow-up no longer having the disorder.8,9 One large, well-conducted 10-year prospective study found that 93% of those with borderline personality disorder had at least a 2-year period of remission, but only 50% also attained good psychosocial functioning.10
In this article, we focus on the current diagnostic criteria for borderline personality disorder, as presented in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR),11and how these criteria can be used to differentiate it from other disorders that may share symptoms. A summary of the evidence used in this review is found in Box 1. We based our review primarily on findings from a relatively small body of experimental studies that used the very similar DSM-III12 and DSM-IV13definitions of borderline personality disorder and its symptoms. Recent research, which was the focus of our review, was generally of high quality and used sophisticated assessment and measurement strategies to differentiate the disorder from other psychiatric disorders.