This is because the DSM-IV describes a mixed episode as a period of at least one week when the standards are met for both a manic (not hypomanic) and a major depressive episode, and the mood disturbance is severe enough to impair job performance, social activities or relationships, or to require hospitalization, or there are psychotic features, and the symptoms are not caused by drug use or a medical condition.
This definition leaves out anyone with bipolar II or cyclothymia, and anyone with bipolar I disorder who experiences both manic and depressive symptoms at the same time but with less severity. It also leaves all those patients who have a combination of symptoms of mania/hypomania and depression with no name for what they're going through.
Understandably, there is pressure both within the psychiatric and psychological community and among people with bipolar disorder to relax the DSM-IV definition.
As long ago as 1921, Dr. Emil Kraepelin described several kinds of mixed states, including excited or agitated depression and depression with isolated manic symptoms1. In 2000, noted bipolar researcher Dr. Hagop Agiskal reported that mania with few depressive symptoms represents the most prevalent kind of mixed or dysphoric mania.2
In a 2005 study3, Benazzi found that more than half of patients diagnosed with major depression also had racing thoughts. He concluded that this condition was a link between major depressive disorder without racing thoughts and bipolar II disorder. It should be noted, though, that people with bipolar II disorder and cyclothymia may also experience depression with anxiety symptoms and/or racing thoughts.
Currently, there is no named diagnosis for this type of episode; hopefully the next edition of the Diagnostic and Statistical Manual of Mental Disorders - DSM-V - will address this as a subtype of mixed episodes.
No one disputes that there are more types of mixed states than the DSM-IV allows. Since the next edition, DSM-V, is not due for publication until 2011, the best doctors and patients can do for now is be very clear to each other just what "mix" of symptoms are present when an episode's symptoms and behaviors include more than pure mania, hypomania or depression. Just saying "It's a mixed episode" is not clear enough.
1Agiskal, H.S. (2000). "Complex Bipolarity: Focus on Temperament and Mixed States." Retrieved October 4, 2006 from http://www.medscape.com/viewarticle/420234.
2Agiskal, H.S. (2000). "Delineating Depressive Mixed States in the Course of Bipolar I Disorder." Retrieved October 4, 2006 from http://www.medscape.com/viewarticle/420324.
3Benazzi, F. (2005). Psychiatry and Clinical Neurosciences 59:5. "Unipolar depression with racing thoughts: A bipolar spectrum disorder?" Retrieved October 5, 2006 from http://www.blackwell-synergy.com/doi/abs/...
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