Problems diagnosing bipolar disorder in clinical practice

Bipolar disorder is a serious illness resulting in significant psychosocial morbidity and excess mortality. During the past few years, a series of research reports, reviews and commentaries have suggested that bipolar disorder is under-recognized, and that many patients, particularly those with major depressive disorder, have, in fact, bipolar disorder [1–10]. Even for those patients diagnosed with bipolar disorder, the lag between initial treatment-seeking and the correct diagnosis is often more than 10 years [11,12]. The treatment and clinical implications of the failure to recognize bipolar disorder in depressed patients include the underprescription of mood-stabilizing medications, an increased risk of rapid cycling and increased costs of care [4,13–15]. Recommendations for improving the detection of bipolar disorder include careful clinical evaluations inquiring about a history of mania and hypomania and the use of screening questionnaires [1,7,8,16].

More recently, some reports have suggested that bipolar disorder is also overdiagnosed at times. For example, Hirschfeld and colleagues interviewed 180 depressed primary care outpatients receiving antidepressant medication with the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (SCID) [17]. In total, 43 patients reported a prior diagnosis of bipolar disorder, and this diagnosis was not confirmed by the SCID in 32.6%. Of note, the overdiagnosis rate of 32.6% was higher than the 21.9% underdiagnosis rate in the 137 patients who had not been previously diagnosed with bipolar disorder. Stewart and El-Mallakh evaluated 21 patients with a substance use disorder who were admitted for residential treatment and had been previously diagnosed with bipolar disorder [18]. Based on the results of a SCID interview, only nine (42.9%) were diagnosed with bipolar disorder. The other 12 patients were diagnosed with a substance-induced mood disorder. Goldberg and colleagues evaluated 85 patients admitted to an inpatient dual diagnosis unit specializing in the treatment of mood and substance use disorders who had been diagnosed with bipolar disorder by their outpatient psychiatrist [19]. Similar to the results of Stewart and El-Mallakh, only a minority of the patients (32.9%) had the diagnosis of bipolar disorder confirmed. None of these studies examined the prevalence of personality disorders using standardized assessment measures.

As part of the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, our clinical-research group conducted the largest study of bipolar disorder underdiagnosis and overdiagnosis [20]. We used the SCID to interview 700 psychiatric outpatients presenting for treatment. Prior to the interview the patients completed a self-administered questionnaire that asked them whether they had been previously diagnosed by a healthcare professional with bipolar or manic-depressive disorder. Diagnoses were blind to the results of the self-administered scale. Family history information was obtained from the patients regarding their first-degree relatives. Slightly more than 20% of the sample reported that they had been previously diagnosed as having bipolar disorder (n = 145, 20.7%), significantly higher than the 12.9% rate based on the SCID. More than half (56.6%, n = 82) of 145 patients who reported that they had been previously diagnosed with bipolar disorder were not diagnosed with bipolar disorder based on the SCID. Bipolar disorder was also underdiagnosed in some patients, but three-times as many patients had been overdiagnosed as had been underdiagnosed (82 vs 27). Patients with SCID-diagnosed bipolar disorder had a significantly higher morbid risk of bipolar disorder in their first-degree relatives than patients who self-reported a previous diagnosis of bipolar disorder that was not confirmed by the SCID. Patients who self-reported a previous diagnosis of bipolar disorder that was not confirmed by the SCID did not have a significantly higher morbid risk for bipolar disorder than the patients who were negative for bipolar disorder by self-report and the SCID. Thus, the results of the study suggested that bipolar disorder was often overdiagnosed, and the family history analyses supported the validity of the diagnostic procedures.

In a follow-up to this initial study, we examined whether there was a particular diagnostic profile associated with bipolar disorder overdiagnosis [21]. We compared the diagnostic characteristics of two groups of patients who were not diagnosed with bipolar disorder based on the SCID interview – those who reported previously being diagnosed with bipolar disorder (n = 82) and those who had not been so diagnosed in the past (n = 528). Patients in the overdiagnosed bipolar group were diagnosed with significantly more axis I disorders, in general, and major depressive disorder, post-traumatic stress disorder, any impulse control disorder, any eating disorder and borderline and antisocial personality disorders, in particular. We conducted a logistic regression analysis to examine which diagnoses were independently associated with bipolar disorder overdiagnosis, and found that only borderline personality disorder, post-traumatic stress disorder and any impulse control disorder were independently associated with bipolar disorder overdiagnosis. Nearly 40% (20 out of 52) of the patients diagnosed with DSM-IV borderline personality disorder had been overdiagnosed with bipolar disorder.

We were not surprised that bipolar disorder overdiagnosis was associated with borderline personality disorder because the phenomenological features of the two disorders overlap. Both are characterized by fluctuations in mood. However, the strong and intense emotions of individuals with borderline personality disorder are often time-limited reactions to how they perceive and believe others are treating them, whereas the mood dysregulation in bipolar disorder is more often sustained. Individuals with borderline personality disorder may do impulsive things that can cause problems, such as gambling, excessive spending of money, sexual promiscuity, excess drug and alcohol use, stealing, eating binges or reckless driving. Individuals with bipolar disorder may engage in similar behaviors, although often these occur during distinct mood episodes. Given the overlap in the features characteristic of these two disorders, it is not surprising that they frequently co-occur. Paris, Gunderson and Weinberg comprehensively reviewed studies reporting the rates of comorbidity between bipolar disorder and borderline personality disorder [22]. In 12 studies of the frequency of bipolar disorder in patients with borderline personality disorder, they found that approximately 10% of the patients with borderline personality disorder were diagnosed with bipolar I disorder, and approximately 10% were diagnosed with bipolar II disorder. In 16 studies of borderline personality disorder co-occurrence in patients with bipolar disorder, approximately 10% of the patients with bipolar I disorder and 16% of patients with bipolar II disorder were diagnosed with borderline personality disorder. Elevated rates of co-occurrence have likewise been found in community surveys [23,24]. However, while there is statistical association, the vast majority of individuals with one of these disorders are not diagnosed with the other.

Why might the phenomenon of false-positive bipolar disorder diagnoses be arising at this time? We believe that the increased availability of medications to treat bipolar disorder, and the accompanying marketing efforts, are chiefly responsible. Many continuing medical education programs on bipolar disorder begin with a summary of research suggesting that bipolar disorder is underdiagnosed, and this is followed by a discussion of methods clinicians can use to improve the detection of the disorder. These discussions of diagnostic practice are usually not balanced by a summary of studies demonstrating overdiagnosis and the risks associated with overdiagnosis. Because clinicians are probably inclined to diagnose disorders that they feel more comfortable treating, we hypothesized that in patients with mood instability who do not meet criteria for a hypomanic episode, physicians are nonetheless inclined to diagnose a potentially medication-responsive disorder, such as bipolar disorder, than a disorder such as borderline personality disorder that is less medication-responsive.

Does whether a patient has bipolar disorder or borderline personality disorder have treatment implications? The efficacy of pharmacological interventions is well established for treating bipolar disorder, particularly bipolar I disorder [25], whereas no medications have been approved for the treatment of borderline personality disorder. However, some medications have been found to be of some benefit for different aspects of borderline personality disorder [22], although not for the syndrome as a whole, and this might be responsible for these patients often being prescribed multiple agents [26]. Evidence continues to emerge establishing the efficacy of certain forms of psychotherapy for borderline personality disorder [27–29]; therefore, overdiagnosing bipolar disorder in patients with borderline personality disorder can result in the failure to recommend the most appropriate forms of treatment.

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.