Background: Bipolar disorder is a highly prevalent mood disorder, frequently misdiagnosed as unipolar major depressive disorder.
Methods: In order to summarize the historical and clinical features that may distinguish bipolar disorder and major depressive disorder, a MedLine search was conducted of all English-language articles published between 1996 and 2006 using the key search terms bipolar disorder and manic-depression cross-referenced with major depressive disorder.
Results: Better methods for arriving at the correct diagnosis of bipolar disorder include a clinical history that evaluates symptoms beyond narrow DSM-IV criteria and the use of self-reported screening tools. Twenty-six separate features were identified that are believed to aid in the differentiation of bipolar disorder from unipolar major depressive disorder.
Conclusions: It is estimated that as many as 1 in 5 depressed outpatients may have undeclared bipolar disorder. Recognition of bipolar disorder can be improved by increasing the clinical acumen of diagnosticians and through the use of screening tools.