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If bipolar disorder is over-diagnosed, what are the actual diagnoses?

July 29, 2009

New Rhode Island Hospital research is follow-up to previous study suggesting that bipolar disorder is over-diagnosed

Providence, RI - A year ago, a study by Rhode Island Hospital and Brown University researchers reported that fewer than half the patients previously diagnosed with bipolar disorder received an actual diagnosis of bipolar disorder after using a comprehensive, psychiatric diagnostic interview tool --the Structured Clinical Interview for DSM-IV (SCID). In this follow-up study, the researchers have determined the actual diagnoses of those patients. Their study is published in the July 28 ahead of print online edition of The Journal of Clinical Psychiatry.

Under the direction of lead author Mark Zimmerman, MD, director of outpatient psychiatry at Rhode Island Hospital, the researchers' findings indicate that patients who received a previous diagnosis of bipolar disorder that was not confirmed by a SCID, they were significantly more likely to be diagnosed with borderline personality disorder as well as impulse control disorders.

Their research involved the study of 82 psychiatric outpatients who reported that they received a previous diagnosis of bipolar disorder that was not later confirmed through the use of the SCID. The diagnoses in these patients were compared to 528 patients who were not previously diagnosed with bipolar disorder. The study was conducted between May 2001 and March 2005.

Zimmerman, who is also an associate professor of psychiatry and human behavior at The Warren Alpert Medical School of Brown University, says, "In our study, one quarter of the patients over-diagnosed with bipolar disorder met DSM-IV criteria for borderline personality disorder. Looking at these results another way, nearly 40 percent (20 of 52) of patients diagnosed with DSM-IV borderline personality disorder had been over-diagnosed with bipolar disorder."

The results of the study also indicate that patients who had been over-diagnosed with bipolar disorder were more frequently diagnosed with major depressive disorder, antisocial personality disorder, posttraumatic stress disorder and eating and impulse disorders.

Zimmerman and colleagues note that "we hypothesize that in patients with mood instability, physicians are inclined to diagnose a potentially medication-responsive disorder such as bipolar disorder rather than a disorder such as borderline personality disorder that is less medication-responsive."

In their previously published study that concluded bipolar disorder was over-diagnosed, they studied 700 patients. Of the 700 patients, 145 reported they had been previously diagnosed as having bipolar disorder; however, fewer than half of the 145 patients (43.4 percent) were diagnosed with bipolar disorder based on the SCID. The authors state that the over-diagnosis of bipolar disorder can have serious consequences, because while bipolar disorder is treated with mood stabilizers, no medications have been approved for the treatment of borderline personality disorder. As a result, over-diagnosing bipolar disorder can unnecessarily expose patients to serious medication side effects, including possible impact to renal, endocrine, hepatic, immunologic and metabolic functions.

Zimmerman concludes, "Because evidence continues to emerge establishing the efficacy of certain forms of psychotherapy for borderline personality disorder, over-diagnosing bipolar disorder in patients with borderline personality disorder can result in the failure to recommend the most appropriate forms of treatment."

Lifespan