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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.

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.

There were no differences among the 3 groups in expectation ratings or mean depression scores after 4 weeks of …