Brief report
Light room therapy effective in mild forms of seasonal affective disorder—A randomised controlled study

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Abstract

Background

The most common way to provide bright light therapy to Swedish patients with Seasonal Affective Disorder (SAD), is treatment in a light therapy room. Since few studies have evaluated treatment provided in this setting and few have evaluated the effect of bright light in sub-clinical SAD (S-SAD), such a study including a one-month follow-up was designed.

Methods

Fifty adults recruited from a previous prevalence study and clinically assessed as having SAD or S-SAD, were randomised to treatment in a light room or to a three-week waiting-list control group. The Hamilton Depression Rating Scale-Seasonal Affective Disorders Self-rating 29-items Version (SIGH-SAD/SR) was used to measure depressive mood at baseline, directly following treatment and at the one-month follow-up.

Results

ANCOVA with adjustment for baseline depression score, showed a significant main effect for the light room therapy group (p < 0.001). Fifty-four percent (n = 13/24) improved ≥ 50% while no such improvement was seen in the control condition (n = 0/24). After merging the two groups, repeated measures ANOVA confirmed the experimental analysis (p < 0.001). At the one-month follow-up, 83.0% (n = 39/47) had improved ≥ 50% and 63.8% (n = 30/47) had normal depression scores, i.e. ≤ 8.

Conclusions

Light room therapy was effective in reducing depressive symptoms in subjects with winter depressive mood. Results were maintained over a period of one month.

Introduction

The most common way to provide bright light therapy (BLT) to Swedish patients with Seasonal Affective Disorder (SAD) (Golden et al., 2005, Lam et al., 2006) is treatment in a light therapy room, but few studies have evaluated treatment in this setting (Thalen et al., 1995). Light room therapy (LRT) is usually provided in hospitals while treatment with light boxes more commonly are given in patients' homes (Terman and Terman, 2006). The two settings used for treatment with BLT differ in several ways and it cannot be assumed that data from either setting is valid for the other. Furthermore, there are few studies on the effect of BLT in subclinical SAD (S-SAD); winter depressive mood that do not meet the criteria for major depression (Kasper et al., 1989, Lam et al., 2001, Levitt et al., 2002). Since most previous studies evaluate short-term effects only, longer follow-up periods are also warranted.

The aim of the present study was to evaluate light room therapy in subjects with winter depressive mood (i.e. SAD and S-SAD) using a waiting-list control group design. A further aim was to evaluate effects over a follow-up period of one month and to estimate some frequently used measures of clinical response.

Section snippets

Subjects and design

Fifty subjects (20–68 years) with winter depressive mood, were recruited from an earlier prevalence study (Rastad et al., 2005) in the county of Dalarna at approximately lat 60.5 N (Fig. 1, step 1). Subjects were interviewed by telephone (C.R.) and subsequently diagnosed by an experienced psychiatrist in a clinical interview, performed before the seasonal symptoms appeared (Fig. 1, steps 2–3).

The inclusion criteria were: (1) a history of major depressive disorder with a winter seasonal pattern

Differences between the LRT and WLC group

Between-group ANCOVA showed a significant main effect; F(1,45) = 16.7, p < 0.001, partial η2 = 0.27 (Table 2). Multiple linear regression analysis showed that the reduction in depression score after LRT was estimated at 9.7 (adjusted mean value, 95% CI: 4.9–14.4, p < 0.001). Corresponding reduction due to baseline depression level was 0.7 (95% CI: 0.4–0.9, p < 0.001), which indicates that the effect of LRT is only slightly better for subjects with high compared to low baseline score. Expressed in

Discussion

The main finding in this study was that ten-day bright light treatment in a light therapy room reduced self-reported depression in subjects with winter depressive mood. Results were maintained at the one-month follow-up.

Analyses of the two subscales, showed similar reductions in both typical and atypical depressive symptoms, which is consistent with results from other studies (Levitt et al., 2002, Terman and Terman, 2006). The results were only slightly affected by baseline severity of

Role of the funding source

The study is supported by the Dalarna County Council, the Center for Clinical Research Dalarna and the Uppsala University. There are no other forms of financial or practical support than those mentioned above.

Conflict of interest

Authors have no commercial or financial involvements that might result in a conflict of interest in connection to the study.

Acknowledgements

Special thanks to the statistical advisor Jan Ifver, Dr Baba Pendse, safety engineer Rasmus Bjurström, dr Kalman Vanky, Tanja Rastad, the late professor P-O Sjödén, participating personnel and patients.

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