MedWire News: Bipolar disorder patients who are in a period of sustained but subsyndromal depression display functional impairments equivalent to their peers who are in a full-blown major depressive episode, study findings suggest.

Compared with patients in complete remission, those with subsyndromal depression showed impairments in satisfaction with quality of life, recreation, work, and relationships of a similar magnitude to patients with a major depressive episode.

The researchers suggest that subsyndromal depression is being overlooked in trials of bipolar disorder, and say the results underscore the need to "target full remission in clinical practice."

While recurring episodes of depression have been consistently associated with poor outcomes in bipolar disorder, relatively less is known about the impact of subsyndromal depressive symptoms - ie those of insufficient intensity to meet criteria for a full depressive mood episode.

"Given that people with bipolar disorder spend approximately one third of their adult lives with depressive symptoms, the impact of depressive symptoms on functional outcomes is particularly relevant," Lauren Marangell (Eli Lilly and Company, Indianapolis, Indiana, USA) and colleagues comment in the Journal of Affective Disorders.

For the study, the researchers recruited a total of 1516 patients with bipolar disorder of whom 1094 were in full clinical remission, 112 had subsyndromal depression, and 310 were experiencing a major depressive episode.

Patients were assessed using the Range of Impaired Function Tool (LIFE-RIFT), which calculates several domains of function with a maximum score of 20 indicating poorest functioning.

Patients in remission had an average score of 9.04, while patients with subsyndromal depression and those with a major depressive episode showed significantly worse functioning with scores of 13.18, and 14.81, respectively.

The only aspect for which subsyndromal depressive and major depressive patients differed significantly was the number of work days missed, with the latter group taking more time off.

Marangell et al conclude: "The current work reinforces the need to attempt multiple trials of medication and medication combinations to strive toward full recovery in all patients and to include subsyndromal symptoms and/or functional outcomes in clinical trials."

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