Mixed state impedes remission in bipolar depression

By Lucy Piper, Senior medwireNews Reporter

Researchers highlight the importance of identifying sub-syndromal manic symptoms in patients experiencing an episode of bipolar depression after finding these less prominent symptoms lengthen the time to remission.

“Nosological recognition of the presence of a mixed state in bipolar disorder is needed in clinical practice to understand the clinical course and treatment responses of patients,” says the team, led by Won-Myong Bahk (The Catholic University of Korea, Seoul).

In their study of 131 inpatients diagnosed with bipolar I or II disorder depression, 70 were classified as having pure depression, 38 as having a sub-threshold mixed state (one or two manic symptoms), and 23 as having a depressive mixed state (more than three manic symptoms).

Patients with a depressive mixed state or a sub-threshold mixed state took significantly longer to achieve remission from the index episode than those with pure depression, at 7.7 and 6.9 months versus 5.1 months, respectively.

This worse disease course in patients with depressive mixed state may be related to them being significantly more likely to have manic symptoms, especially inflated self-esteem and psychomotor agitation, in the index episode than patients with pure depression, the researchers suggest.

“These manic symptoms are associated with the serious clinical outcomes of bipolar mixed states, such as longer affective episodes and exacerbation of manic symptoms of syndromal mania,” they explain in the Journal of Affective Disorders.

The team adds that the presence of manic symptoms may also increase patients’ susceptibility to bipolar factors associated with poorly regulated affective instability.

Other clinical differences included psychotic features being more common in the index episode in patients with a depressive mixed state than in those with a sub-threshold mixed state. And both groups of mixed-state patients had a younger age at disease onset and at first treatment than patients with pure depression, albeit not significantly so.

“[T]hese findings contribute to the literature concerning the course of previously undiagnosed mixed episodes,” say Bahk et al, who note that these symptoms can often be overlooked in a routine assessment.

The researchers conclude: “[T]he results of the present study demonstrate that patients experiencing sub-syndromal manic symptoms during an episode of bipolar depression have different clinical characteristics and a more severe illness course, including a longer time to remission, than do those with a pure depressive state.”

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