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nightsurfer on 2009-08-26Seasonal affective disorder (SAD) is a type of winter-time depression experienced by people those who live in northern latitudes such as those of New York, Seattle, all of Canada, and Northern Europe. I believe it is primarily a disorder of sunlight/vitamin D deficiency.
Vitamin D, when administered in late winter, produces a positive effect on mood in only five days. One theory for this is that vitamin D stimulates the brain to produce more serotonin. In a wintertime experiment, serum vitamin D levels doubled in six months through supplementation and dramatically increased scores on a wellbeing assessment. Two groups were given either 1,000 IU or 4,000 IU of vitamin D daily. And although both groups improved, the higher dose produced better results.