Bipolar nature of depression with depressive mixed states

--------------------------------------------------------------------------------

http://www.psychiatrysource.com/psyc...rticle2100.htm

Seasonality shows bipolar nature of depression with depressive mixed states
16 Jan 2006

Researchers have found that unipolar depression with depressive mixed states (DMX) has a seasonal pattern similar to that of bipolar depression, providing further evidence of the bipolar nature of this condition.

Noting that the seasonality of depressive episodes has been indicated to be different between unipolar and bipolar depression, investigators from Ludwig-Maximilian University in Munich, Germany, studied how the seasonal pattern of depressive episodes in patients with unipolar depression with DMX compared.

Tetsuya Sato and colleagues looked at the onset of index depressive episodes during each of the 12 calendar months over a 6-year period for 95 patients with bipolar depression, and 77 unipolar depressive patients with and 786 without DMX.

DMX were defined as the presence of two or more of eight manic or manic-related symptoms: flight of idea, logorrhea, aggression, excessive social contact, increased drive, irritability, racing thoughts, and distractibility.

For the patients with unipolar depression without DMX, the results showed a large peak in the onset of depressive episodes in the spring, while for the participants with bipolar depression, there was a significant peak in the fall.

The researchers note that the seasonal pattern for patients with unipolar depression with DMX was similar to that seen for bipolar depression patients, with the onset of episodes peaking in the fall.

Moreover, analysis showed that the monthly distribution of onsets of depressive episodes in unipolar patients without DMX was significantly different from that in bipolar patients and unipolar patients with DMX combined.

"The findings suggest that unipolar depression with DMX has a distinct seasonal pattern as compared to unipolar depression without DMX; and that unipolar depression with DMX may share similar neurobiological mechanisms related to sensitivity to season with bipolar depression," Sato and team write in the Journal of Affective Disorders.

The results further support the hypothesis that "unipolar depression with DMX should be classified into bipolar disorder," they say.


Source: J Affect Disord 2006; 90: 1–5