A placebo-controlled trial of light treatment for winter depression.

We studied 32 patients with winter seasonal affective disorder (SAD) in a counterbalanced crossover design comparing 1 h of morning light treatment (about 7000 lux) to 1 h of morning placebo treatment (deactivated negative ion generator). Both treatments significantly reduced depression ratings, but there was no difference between the antidepressant response to light and to placebo. Several possible explanations for this result were discussed including an inadequate 'dose' of light (e.g., ineffective duration or intensity), an unusual sample of patients, and a placebo mechanism.