By Eleanor McDermid, Senior medwireNews Reporter
Researchers say that there are clear clinical differences between depressed patients with bipolar II disorder and those with borderline personality disorder, which supports the two being treated as distinct conditions.
The 62 bipolar II disorder patients in the study were distinguished mainly by a significantly higher likelihood for having first-degree relatives with bipolar disorder, at 5.9% compared with 3.0% of the 206 patients who had major depressive disorder with borderline personality disorder (MDD-BPD).
“During the past few years, our clinical-research group has identified a problem with the overdiagnosis of bipolar disorder that is at least as frequent as the problem with underdiagnosis,” say lead researcher Mark Zimmerman (Rhode Island Hospital, Providence, USA) and team.
They admit that their claim has been disputed, but say that those patients they considered to have been overdiagnosed had a family risk for bipolar disorder that was similar to that of patients without the disorder, but markedly lower than that seen for patients considered to genuinely have the condition.
“The results of the present study extend our prior findings and support the validity of distinguishing between bipolar disorder and BPD,” they comment in the Journal of Clinical Psychiatry.
Patients with MDD-BPD had a number of distinguishing factors. They had an average of 2.7 Axis I disorders, compared with 1.8 in the bipolar disorder patients, and 38.4% versus 25.8% had three or more disorders. Of the individual disorders, posttraumatic stress disorder was the only one that was significantly more common in MDD-BPD than bipolar patients, at 30.1% versus 9.7%.
The MDD-BPD patients also had more personality disorders than the bipolar patients (56.7 vs 38.5%) and had more severe depressive symptoms, including higher scores for anger, anxiety, paranoid ideation, and somatization. MDD-BPD patients had poorer social functioning than patients with bipolar II depression, and had made more suicide attempts.
Zimmerman et al note that they diagnosed bipolar II disorder according to the DSM-IV criteria, which require hypomania to last at least 4 days. They say that if a more relaxed definition was applied, as some have advocated, “[i]t is likely that the transient periods of affective instability characterized by anger and irritability that are typical of borderline personality disorder would be more often misinterpreted as indicative of a hypomanic episode.”
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