Borderline personality disorder and the misdiagnosis of bipolar disorder

Abstract

Recent reports suggest bipolar disorder is not only under-diagnosed but may at times be over-diagnosed. Little is known about factors that increase the odds of such mistakes. The present work explores whether symptoms of borderline personality disorder increase the odds of a bipolar misdiagnosis. Psychiatric outpatients (n = 610) presenting for treatment were administered the Structured Clinical Interview for DSM-IV (SCID) and the Structured Interview for DSM-IV Personality for DSM-IV axis II disorders (SIDP-IV), as well as a questionnaire asking if they had ever been diagnosed with bipolar disorder by a mental health care professional. Eighty-two patients who reported having been previously diagnosed with bipolar disorder but who did not have it according to the SCID were compared to 528 patients who had never been diagnosed with bipolar disorder. Patients with borderline personality disorder had significantly greater odds of a previous bipolar misdiagnosis, but no specific borderline criterion was unique in predicting this outcome. Patients with borderline personality disorder, regardless of how they meet criteria, may be at increased risk of being misdiagnosed with bipolar disorder.

Introduction

For years, a consensus had emerged that bipolar disorder was being under-diagnosed (e.g., Akiskal et al., 2000, Bowden, 2001, Ghaemi et al., 1999, Ghaemi et al., 2000, Hirschfeld, 2001, Lish et al., 1994, Manning et al., 1997, Perugi et al., 1998). A recent report, however, showed a dramatic shift in this trend, with the rate of bipolar diagnosis among outpatient office-based visits doubling in the last decade among adults and rising nearly 40-fold among children and adolescents (Moreno et al., 2007). A subsequent study from our group provided evidence of potential misdiagnosis of bipolar disorder (Zimmerman et al., 2008).

Little work has considered factors associated with the possible overdiagnosis of bipolar disorder. One source of error may involve confusing symptoms of borderline personality disorder with bipolar disorder. Although the disorders are clearly distinct as defined by the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 2000), a number of shared phenomenological features make the latter hypothesis plausible. Affective instability is a core feature of both disorders, albeit the nature and course of this instability may differ (Henry et al., 2001, Koenigsberg et al., 2002). The difficulty controlling anger often seen in patients with borderline personality disorder might be confused with the irritability of a manic episode (American Psychiatric Association, 2000). Impulsivity is a hallmark of borderline personality disorder, but is also common in patients with bipolar disorder even outside of episodes (Links et al., 1999, Swann et al., 2003, Zanarini, 1993). Both disorders are also often characterized by recurrent suicide attempts (Fyer et al., 1988, Ruggero et al., 2007, Zanarini et al., 2008) and problematic social functioning (American Psychiatric Association, 2000, Bauwens et al., 1991, Dion et al., 1988, Fagiolini et al., 2005, Weinstock and Miller, 2008). Similarities between the two disorders have even prompted some to question whether they belong to the same spectrum, although evidence for this hypothesis remains mixed (Akiskal et al., 1985, Akiskal, 2002, Benazzi, 2008, Deltito et al., 2001, Gunderson et al., 2006, Koenigsberg et al., 2002, Mackinnon and Pies, 2006, Magill, 2004, Paris et al., 2007, Smith et al., 2004, Wilson et al., 2007).

In this report from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project (Zimmerman, 2003) we assess the extent to which specific features of borderline personality disorder may put a patient at risk of being misdiagnosed with bipolar disorder. Based on the similar phenomenological features discussed above, we hypothesized that the borderline criteria reflecting affective instability, anger, impulsivity, recurrent suicidal behavior, and interpersonal instability would be most associated with bipolar misdiagnosis.