Calibration of response and remission cut-points on the Beck Depression Inventory-Second Edition for monitoring seasonal affective disorder treatment outcomes

Abstract

Background

The purpose of this study is to define treatment response and remission cut-point scores for the Beck Depression Inventory—Second Edition (BDI-II) when used to monitor seasonal affective disorder (SAD) treatment.

Methods

Data from two published randomized clinical trials for SAD were utilized to complete a ROC analysis to define response and remission thresholds for the BDI-II. The Structured Interview Guide for the Hamilton Rating Scale for Depression—Seasonal Affective Disorder Version (SIGH-SAD) was used as a reference standard. Data from the two trials included BDI-II and SIGH-SAD scores for patients at baseline, 6 weeks (post-treatment), and 1 year (next winter).

Results

BDI-II score of ≤ 9 was the derived criterion for remission of SAD, and BDI-II score decrease of 50% from baseline was the criterion for treatment response.

Limitations

Study participants were primarily female (94%) and Caucasian (80%) so demographic diversity of the sample was limited.

Conclusion

This study validated BDI-II scores compared to the SIGH-SAD reference standard. The BDI-II has greater potential for widespread use by clinicians than the SIGH-SAD to monitor SAD patients because it is a brief self-report instrument that can be conveniently administered in the waiting room.

Introduction

Standardized outcome tools help the practicing clinician distinguish response (partial symptom reduction) from remission (full return to healthy functioning). This distinction is important in depression treatment, since patients often fail to achieve remission after an adequate treatment trial (Trivedi et al., 2006). A prospective, naturalistic study of individuals with a first lifetime major depressive episode found that patients with incomplete remission of depression experienced more rapid depression recurrence and had more chronic major depressive episodes (> 2 years) compared to patients who achieved full remission. (Judd et al., 2000). Patients with residual depression symptoms have also demonstrated worse social/relationship and occupational outcomes compared to patients who achieved remission (Kennedy and Paykel, 2004).

A challenge, however, in using outcome measures to determine treatment response and remission is that scores may not be validated for specific depression subgroups. One subtype of major depressive disorder is seasonal affective disorder (SAD). Patients with SAD experience marked changes in mood and activity over the fall/winter months and spontaneous remission of symptoms in the spring/summer. These patients often present with significant atypical depressive symptoms, including low energy, increased appetite/weight gain, hypersomnia, and carbohydrate craving (Rosenthal et al., 1984). Individuals with SAD often require ongoing monitoring because of the highly recurrent nature of this disorder (Sakamoto et al., 1995, Schwartz et al., 1996), and the seasonal pattern of symptoms allows for a more predictable time frame to assess for recurrence of symptoms. Prevention of subsequent mood episodes and early intervention is a major public health concern in SAD management (Rohan et al., 2009). In one study of over 1000 SAD patients, individuals reported an average of 13 previous seasonal depression episodes (Modell et al., 2005).

A standard clinical research tool to assess SAD symptom severity and treatment response is the Structured Interview Guide for the Hamilton Rating Scale for Depression—Seasonal Affective Disorder Version (SIGH-SAD; Williams et al., 1992). However, this rater administered tool is not widely used in community treatment because of required training and lengthy administration time.

The Beck Depression Inventory—Second Edition (BDI-II; Beck et al., 1996b) is a commonly used treatment outcome measure for non-seasonal depression. In contrast to the SIGH-SAD, the BDI-II can be used in both primary and specialty care settings because it is a self-report measure and takes only 5–10 min to complete.

To our knowledge, the BDI-II has never been calibrated to the SIGH-SAD, the reference standard in SAD research, in order to establish appropriate cut-point scores for SAD treatment response and remission. The purpose of this study was to identify appropriate BDI-II threshold scores to define “response” and “remission” in SAD treatment. We did so by comparing BDI-II and SIGH-SAD scores of SAD patients treated in a randomized clinical trial. Patient assessments using both instruments were completed at baseline, after the 6-week treatment phase, and at a 1-year naturalistic follow-up the next winter.