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

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.