Sixteen depressed patients with seasonal affective disorder participated
in a double-blind crossover study comparing the antidepressant effects of 2
hours of early morning and 2 hours of early afternoon therapy with bright
light. They responded equally well to both treatments. These results
suggest that the antidepressant effects of phototherapy in seasonal
affective disorder do not depend on its capacity to extend day length
(photoperiod) and are not likely to be due to a shift in the timing of
circadian rhythms. These findings have practical implications for the
administration of phototherapy in the treatment of seasonal affective
disorder.
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