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Original Article
October 1998

Bright Light Treatment of Winter Depression: A Placebo-Controlled Trial

Author Affiliations

From the Biological Rhythms Research Laboratory, Departments of Psychology (Drs Eastman and Liu) and Psychiatry (Drs Young, Fogg, and Meaden), Rush-Presbyterian-St Luke's Medical Center, Chicago, Ill.

Arch Gen Psychiatry. 1998;55(10):883-889. doi:10.1001/archpsyc.55.10.883
Abstract

Background  Bright light therapy is the recommended treatment for winter seasonal affective disorder (SAD). However, the studies with the best placebo controls have not been able to demonstrate that light treatment has a benefit beyond its placebo effect.

Methods  Ninety-six patients with SAD completed the study. Patients were randomly assigned to 1 of 3 treatments for 4 weeks, each 1.5 hours per day: morning light (average start time about 6 AM), evening light (average start about 9 PM), or morning placebo (average start about 6 AM). The bright light (≈6000 lux) was produced by light boxes, and the placebos were sham negative-ion generators. Depression ratings using the Structured Interview Guide for the Hamilton Depression Rating Scale, SAD version (SIGH-SAD) were performed weekly.

Results  There were no differences among the 3 groups in expectation ratings or mean depression scores after 4 weeks of treatment. However, strict response criteria revealed statistically significant differences; after 3 weeks of treatment morning light produced more of the complete or almost complete remissions than placebo. By 1 criterion (24-item SIGH-SAD score <50% of baseline and ≤8), 61% of the patients responded to morning light, 50% to evening light, and 32% to placebo after 4 weeks of treatment.

Conclusions  Bright light therapy had a specific antidepressant effect beyond its placebo effect, but it took at least 3 weeks for a significant effect to develop. The benefit of light over placebo was in producing more of the full remissions.

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