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Lancet. 1990 Sep 22;336(8717):703-6.

Seasonal affective disorder and season-dependent abnormalities of melatonin suppression by light.

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Department of Psychiatry, University of Southamptom, Royal South Hants Hospital, UK.


Twelve patients with seasonal affective disorder (SAD) and eleven normal controls were exposed to 2000 lux and 300 lux of artificial full-spectrum light on consecutive nights during the winter. Suppression of melatonin secretion under the two light intensities was measured and the difference between their effects was taken as a measure of light sensitivity. The test was repeated in summer in both groups, when the SAD subjects were well. The SAD but not the normal group showed a significant seasonal variation in sensitivity to light. There was evidence of supersensitivity in the winter but also of subsensitivity to light in the summer.

[Indexed for MEDLINE]

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