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

Abstract

Background

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

Methods

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.

Results

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.

Limitations

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

Conclusions

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.

Introduction

People with bipolar disorder have episodically impaired psychosocial functioning (Coryell et al., 1993, Bauwens et al., 1991, Gitlin et al., 1995, Bauer et al., 2001, Altshuler et al., 2002, Calabrese et al., 2003), and some degree of functional impairment is evident even during remissions (Cooke et al., 1996, Shapira et al., 1999, MacQueen et al., 2000). MacQueen et al. (2001) reported that up to 60% of individuals with bipolar disorder do not regain full functioning in occupational and social domains (MacQueen et al., 2001). Ongoing depressive symptoms are the strongest predictor of functional deficits in persons with bipolar disorder (Bauer et al., 2001, Judd et al., 2005). While recurring episodes of depression are clearly associated with poor outcomes, relatively less is known about the impact of subsyndromal depressive symptoms, or depressive symptoms of insufficient number, duration, and/or intensity to meet criteria for a full depressive mood episode. The presence of subsyndromal symptoms after resolution of a major affective episode is associated with increased risk for relapse (Perlis et al., 2006, Judd et al., 2008). The current investigation is concerned with the relationship of persistent subsyndromal symptoms to functional outcomes. Given that people with bipolar disorder spend approximately one third of their adult lives with depressive symptoms (Judd et al., 2002, Judd et al., 2003), the impact of depressive symptoms on functional outcomes is particularly relevant. In a study following patients for 2–4 years, almost half of those who did not experience full episodic relapse experienced significant affective symptoms. In contrast to relapse rates, a measure of cumulative affective morbidity was the strongest predictor of functional outcome in this study (Gitlin et al., 1995). Similarly, Bauer et al. (2001) reported that both number of weeks in a full depressive episode and average depression symptom score (including subsyndromal symptoms) were significantly related to functional outcomes. Two studies of euthymic patients in ongoing care demonstrated relationships between subsyndromal HAM-D scores and social adjustment (Shapira et al., 1999) and function (Cooke et al., 1996). A small study of 25 men with bipolar disorder indicated a relationship between subsyndromal depressive symptoms and function as measured by the GAF (Altshuler et al., 2002). In order to further elucidate the relationship between subsyndromal depressive symptoms, social and vocational function, and quality of life in bipolar disorder, we examined these variables in participants in the Systematic Treatment Enhancement Program for Bipolar Disorder (“STEP-BD”; Sachs et al., 2003).