Over-diagnosis of bipolar disorder and disability payments -- a link?

This study is based on previous work led by Mark Zimmerman, MD, director of outpatient psychiatry at Rhode Island Hospital. The previous research involved 700 psychiatric outpatients who were interviewed using the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (SCID) along with a self-administered questionnaire. The questionnaire asked whether the patient had been previously diagnosed with bipolar or manic-depressive disorder by a health care professional. Of the 700 patients, 145 of those had been previously diagnosed, yet fewer than half of those (43 percent) received a confirmed diagnosis using the SCID. The 82 patients who did not receive a confirmed diagnosis were then classified as the over-diagnosed patients.

In this study, the researchers examined whether a secondary gain such as receiving disability payments might be partially responsible for the over-diagnosis. The 82 over-diagnosed patients from the previous survey were compared to 528 patients who were not diagnosed with bipolar disorder. These patients were interviewed by a diagnostic rater who administered a modified version of the SCID to inquire whether patients had received long-term disability payments because of psychiatric illness in the past five years, and for what length of time they received payments.

Zimmerman says, "We recognize that bipolar disorder is sometimes a severe, chronic illness that interferes with an individual's ability to maintain gainful employment. Yet when we compared patients who had never been diagnosed with bipolar disorder to the group that we consider over-diagnosed, the over-diagnosed group was significantly more likely to have received disability payments, and for a significantly longer period of time."

Zimmerman, who is also an associate professor of psychiatry and human behavior at The Warren Alpert Medical School of Brown University, explains the possible reasons for the association between receiving disability payments and the over-diagnosis of bipolar disorder. The patients may have over-reported symptoms to meet the criteria for a bipolar disorder diagnosis if they thought it would qualify them for disability payments, but this is unlikely because they did not do so in the SCID interview. "We believe it is more likely that clinicians sometimes over-diagnose bipolar disorder in complex, chronically ill patients with long histories of depression with co-morbidities that share features of bipolar disorder." These types of patients are also more likely to be disabled by their psychiatric illness.

The researchers also note that attempts to engage some patients in discussions about alternative diagnostic possibilities or psychotherapeutic interventions instead of pharmacotherapy are sometimes met with resistance. "Not only have we observed bipolar disorder over-diagnosis in our practice, but we have been impressed with some patients' investment in this diagnosis. We propose that this diagnostic label may be embraced because of the secondary gain accrued from receiving disability payments."

The findings are limited in that it was conducted in a single outpatient practice, but the researchers believe they are significant enough to be studied in a larger group.

Other researchers involved in the study with Zimmerman include Janine Galione, BA; Camila Ruggero, PhD, Iwona Chelminski, PhD, Kristy Dalrymple, PhD and Diane Young, PhD, all of Rhode Island Hospital and Brown University. The original study was based on an analysis of data collected as part of the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) Project, for which Zimmerman is the principal investigator. It is a unique integration of research quality diagnostic methods into a community-based outpatient practice affiliated with an academic medical center.