Date: 07 Sep 2006

The continuum/spectrum concept of mood disorders: is mixed depression the basic link?

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Abstract

Background

Mixed states, i.e., opposite polarity symptoms in the same mood episode, question the bipolar/unipolar splitting of mood disorders, and support a spectrum view. Study aim was assessing the distribution of intradepressive hypomanic symptoms between bipolar-II (BP-II) and major depressive disorder (MDD) depressions, and testing a dose–response relationship between number of intradepressive hypomanic symptoms and bipolar family history. No bi-modality, and a dose–response relationship, would not support a categorical distinction.

Methods

Consecutive 389 BP-II and 261 MDD depressed outpatients were interviewed by the structured clinical interview for DSM-IV, hypomania interview guide, and family history screen, by a mood specialist psychiatrist, in a private practice. Intradepressive hypomanic symptoms were systematically assessed. Mixed depression was defined as the combination of depression and three or more intradepressive hypomanic symptoms, a validated definition.

Results

BP-II, versus MDD, had significantly more intradepressive hypomanic symptoms. The distribution of intradepressive hypomanic symptoms between BP-II and MDD was not bi-modal but normal-like, and a dose–response relationship was found between the number of intradepressive hypomanic symptoms and bipolar family history.

Conclusions

Study findings question the categorical division of BP-II and MDD, and may support the spectrum view of mood disorders.