The prevalence and burden of bipolar depression

BACKGROUND: Bipolar disorder is characterized by debilitating episodes of depression and mood elevation (mania or hypomania). For most patients, depressive symptoms are more pervasive than mood elevation or mixed symptoms, and thus have been reported in individual studies to impose a greater burden on affected individuals, caregivers, and society. This article reviews and compiles the literature on the prevalence and burden of syndromal as well as subsyndromal presentations of depression in bipolar disorder patients. METHODS: The PubMed database was searched for English-language articles using the search terms "bipolar disorder," "bipolar depression," "burden," "caregiver burden," "cost," "costs," "economic," "epidemiology," "prevalence," "quality of life," and "suicide." Search results were manually reviewed, and relevant studies were selected for inclusion as appropriate. Additional references were obtained manually from reviewing the reference lists of selected articles found by computerized search. RESULTS: In aggregate, the findings support the predominance of depressive symptoms compared with mood elevation/mixed symptoms in the course of bipolar illness, and thus an overall greater burden in terms of economic costs, functioning, caregiver burden, and suicide. LIMITATIONS: This review, although comprehensive, provides a study-wise aggregate (rather than a patient-wise meta-analytic) summary of the relevant literature on this topic. CONCLUSION: In light of its pervasiveness and prevalence, more effective and aggressive treatments for bipolar depression are warranted to mitigate its profound impact upon individuals and society. Such studies could benefit by including metrics not only for mood outcomes, but also for illness burden.