The functional impact of subsyndromal depressive symptoms in bipolar disorder: data from STEP-BD

This report describes baseline characteristics and functional outcomes of subjects who have prospectively observed subsyndromal symptoms after a major depressive episode (MDE).

All subjects were participants in the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). We identified subjects with at least 2 years of observation whose prior or current episode was a MDE, and who were in a stable clinical state of either recovered (no more than 2 moderate symptoms for at least 8 weeks), a MDE by DSM-IV criteria, or with continued subsyndromal symptoms. The subsyndromal group was defined a priori as 3 or more moderate affective symptoms but without meeting diagnostic criteria for major depression.

The final cohort included 1094 recovered, 112 subsyndromal, and 310 individuals in a MDE. The average time spent in each clinical status ranged from 120 to 132 days. The subsyndromal group was most similar to those in a MDE, differing only on the intensity of depressive symptoms and the number of work days missed due to ongoing symptoms. Reported sadness, inability to feel and lassitude were each associated with multiple measures of impairment.

This study is limited by the cross-sectional approach to defining outcomes.

These findings are consistent with studies in unipolar major depression that indicate that functional impairment observed in the context of subsyndromal depressive symptoms is comparable to that of a full episode. This work underscores the need to include subsyndromal symptoms in study outcomes and to target full remission in clinical practice.