Misdiagnosed patients with bipolar disorder: comorbidities, treatment patterns, and direct treatment costs.

OBJECTIVE: The purpose of this study was to examine comorbidities, treatment patterns, and direct treatment costs of patients with bipolar disorder who are misdiagnosed with unipolar depression.

METHOD: This study is a retrospective analysis of data from the MarketScan Commercial Claims and Encounters (CCE) database. Logistic regressions and analyses of variance were used to compare the misdiagnosis cohort to 3 age- and gender-matched comparison cohorts (recognized bipolar, depression, and no psychiatric disorders based on ICD-9-CM criteria) during the year 2000.

RESULTS: Each cohort had 769 individuals (68.0% female; mean age of roughly 42 years). The misdiagnosis cohort had higher rates of several psychiatric comorbidities than the depression cohort (e.g., personality disorders, alcohol abuse, psychotic disorder) and the bipolar cohort (e.g., generalized anxiety disorder, panic) but a lower rate of psychotic disorders than the bipolar cohort (p < .05). Compared with the bipolar cohort, the misdiagnosis cohort was more likely to receive antidepressants, but less likely to receive anticonvulsants, antipsychotics, or lithium (all p < .001). Antidepressant rates were similar among the misdiagnosis and depression cohorts. Group differences were found in mean annual costs for anticonvulsants, antipsychotics, lithium, antidepressants, and total treatment costs: bipolar (USD $442, $310, $67, $497, $8600); misdiagnosis (USD $221, $185, $20, $704, $8761); depression (USD $70, $74, $5, $657, $7288).

CONCLUSION: Misdiagnosed bipolar patients received inappropriate and costly treatment regimens involving overuse of antidepressants and underuse of potentially effective medications. Patterns of psychiatric comorbidity suggest one possible strategy for improving recognition of bipolar disorder among patients presenting with depressive symptoms. Patients who present with the observed pattern of comorbidities may benefit from additional screening for bipolar disorder. It is recommended that steps be taken to minimize misdiagnosis in clinical settings.