Am J Psychiatry 1991; 148:509-511
Copyright © 1991 by American Psychiatric Association
Treatment of seasonal affective disorder with green light and red light
DA Oren, GC Brainard, SH Johnston, JR Joseph-Vanderpool, E Sorek and NE Rosenthal
Department of Neurology, Jefferson Medical College, Philadelphia.
OBJECTIVE: This study sought to determine whether an equal photon density
of green light is superior to red light in treating seasonal affective
disorder. METHOD: After recruitment through the media, 20 outpatients with
seasonal affective disorder participated in a balanced- order crossover
trial of 1 week of green light therapy compared with 1 week of red light
therapy. Each treatment consisted of 2 hours of daily light treatment at
home in the early morning. Ultraviolet light was excluded from both
treatment conditions. The photon densities of the two treatments (2.3 x
10(15) photons/sec per cm2) were similar to those used in previous studies
of therapy with 2500-lux white light. Fourteen patients completed the
study. At least 1 week separated each treatment period to allow time for
relapse. Effectiveness of treatment was assessed by analysis of variance of
changes in ratings on the Hamilton Rating Scale for Depression. RESULTS:
Although patients' expectations of the two treatments were similar, green
light induced greater antidepressant effects than red light. A Sequence by
Color interaction was also demonstrated. CONCLUSIONS: Green light provides
a treatment effect superior to that of red light and similar to that seen
in previous studies with white light. These results are consistent with the
hypothesis that retinal photoreceptors mediate the antidepressant response
in seasonal affective disorder. Identifying optimal wavelengths for light
treatment is important in optimizing phototherapy efficacy.
