Discriminating Between Bipolar Disorder and Major Depressive Disorder.

Rates of misdiagnosis between major depressive disorder and bipolar disorder have been reported to be substantial, and the consequence of such misdiagnosis is likely to be a delay in achieving effective control of symptoms, in some cases spanning many years. Particularly in the midst of a depressive episode, or early in the illness course, it may be challenging to distinguish the 2 mood disorders purely on the basis of cross-sectional features. To date, no useful biological markers have been reliably shown to distinguish between bipolar disorder and major depressive disorder.