Abstract

The results of recent community epidemiological research are reviewed, documenting that major depressive disorder (MDD) is a highly prevalent, persistent, and often seriously impairing disorder, and that bipolar disorder (BPD) is less prevalent but more persistent and more impairing than MDD. The higher persistence and severity of BPD results in a substantial proportion of all seriously impairing depressive episodes being due to threshold or subthreshold BPD rather than to MDD. Although the percentage of people with mood disorders in treatment has increased substantially since the early 1990s, a majority of cases remain either untreated or undertreated. An especially serious concern is the misdiagnosis of depressive episodes due to BPD as due to MDD because the majority of depression treatment involves medication provided by primary care doctors in the absence of psychotherapy. The article closes with a discussion of future directions for research.