Clinical characteristics of depressed outpatients previously overdiagnosed with bipolar disorder.

The diagnosis of bipolar disorder in depressed patients requires the ascertainment of prior episodes of mania and hypomania. Several research reports and commentaries have suggested that bipolar disorder is underrecognized and that many patients with nonbipolar major depressive disorder have, in fact, bipolar disorder. In a previous article from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, we reported the opposite phenomenon-that bipolar disorder is often overdiagnosed in psychiatric outpatients. An important question that has not been previously examined is whether there is a particular clinical or demographic profile associated with bipolar disorder overdiagnosis among depressed patients. Forty psychiatric outpatients with current major depressive disorder reported having been previously diagnosed with bipolar disorder, which was not confirmed when interviewed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID). Psychiatric diagnoses, clinical and demographic variables were compared in these 40 patients and 233 depressed patients who were not diagnosed with bipolar disorder. Patients were interviewed by a highly trained diagnostic rater who administered the SCID for DSM-IV Axis I disorders, the Structured Interview for DSM-IV Personality for DSM-IV Axis II disorders, and the Schedule for Affective Disorders and Schizophrenia for clinical features of depression. The depressed patients who were overdiagnosed with bipolar disorder were diagnosed with a significantly higher number of Axis I disorders and were more likely to be diagnosed with specific phobia, posttraumatic stress disorder, and drug abuse/dependence. The patients overdiagnosed with bipolar disorder were also significantly more likely to be diagnosed with a current personality disorder and were more chronically ill with greater psychosocial impairment. Thus, the results suggest that depressed outpatients who had previously been overdiagnosed with bipolar disorder were more chronically and severely ill than depressed outpatients who had not been overdiagnosed.