APA: Bipolar Disorder Both Under- and Overdiagnosed

By John Gever
WASHINGTON, 09 may 2008-- More than half the patients who were told they have bipolar disorder may have been misdiagnosed, even as it goes unrecognized in a substantial number of those who really do have it, a researcher said here.
In 145 psychiatric outpatients who said they had been previously diagnosed with bipolar disorder, the condition was ruled out in 56.6% after they underwent the Structured Clinical Interview for DSM-IV, the diagnostic "gold standard," said Mark Zimmerman, M.D., of Brown University in Providence, R.I.
The structured evaluation also revealed that, of 555 other patients who had not previously received a diagnosis of bipolar disorder, 27 actually did have the condition, Dr. Zimmerman told attendees at the American Psychiatric Association meeting.
All told, out of 700 psychiatric outpatients, 90 were diagnosed with bipolar disorder with the structured interview. The disorder had gone unrecognized in nearly one-third of them, Dr. Zimmerman said.
The research was also published simultaneously online in the Journal of Clinical Psychiatry.
Dr. Zimmerman blamed the overdiagnosis of bipolar disorder on drug companies and others seeking to reduce under-diagnosis, which he said was also a real problem.
"I think there has been a marketing campaign and it has had an impact," Dr. Zimmerman said.
Noting the frequency with which patients ask if they are bipolar, he added, "I've never had a patient come into my office and ask, 'Do I have borderline personality disorder?'"
The study was part of a larger investigation in which 2,500 patients presenting at an outpatient psychiatric clinic filled out questionnaires. For the most recent 700 patients, the questionnaire asked whether the patient had previously received a diagnosis of bipolar disorder.
Dr. Zimmerman acknowledged that the reliance on self-reports, without review of clinical records, was a limitation of the study.
All patients were subsequently evaluated with the Structured Clinical Interview for DSM-IV and other validated instruments.
The evaluation confirmed the diagnosis of bipolar disorder in only 63 of the 145 patients reporting a previous bipolar diagnosis.
The investigators examined family histories of those who did not have a bipolar diagnosis. They found no differences in the prevalence of bipolar disorder in first-degree relatives between those never diagnosed with the condition and those whose initial diagnosis was overturned in the structured interview.
Dr. Zimmerman said the finding confirmed the validity of the structured evaluation process.
He said that overdiagnosis of bipolar disorder leads to over-treatment with mood stabilizers, putting patients at risk for liver, kidney, and metabolic side effects. Patients with such diagnoses may also be more likely to receive drug therapies than counseling.
Although Dr. Zimmerman's presentation was titled "Is Bipolar Disorder Overdiagnosed?", he said the study also supported the more prevalent view that it is under-diagnosed, given that bipolar disease had been missed in 27 of 90 genuinely bipolar patients.
He said bipolar disorder may go unrecognized for a variety of reasons. Depression symptoms typically last much longer than mania, hypomanic patients usually don't seek treatment, and clinicians often fail to ask enough questions to arrive at a correct diagnosis.
The study's single-center design was a limitation, Dr. Zimmerman said. Patients were predominantly white and female, and 40% were college graduates, so it may not be entirely generalizable to other populations.
Funding information was not provided. No potential conflicts of interest were reported.
Primary source: Journal of Clinical PsychiatrySource reference:Zimmerman M, et al "Is bipolar disorder overdiagnosed?" Journal of Clinical Psychiatry 2008; 69:e1-e6/pii: ej07m03888.