My Mother has SAD, suffered for years with it in various parts of CA (too much gloom during winter, even though the days were long and sunny spring-autumns), but now lives in a northern mid-west state. We discovered that SAD doesn't affect her as much there for a couple reasons we can only guess at. The sun was out more often even on bone-chilling days, and the snow on the ground reflecting the light was far, far better for her than the gloomy rainy winter days of CA.
It was a nice surprise that a colder/Winter state was better for her particular SAD. Seems very counter-intuitive at first, but sometimes an individual's needs aren't so clear. And I just gotta reiterate... the snow reflecting more light into a home, combined with it adding the whole ambiance of a Winter look (rather than the sight of gloom or leafless plants in a more temperate state during winter) seems to have a real beneficial effect. Of course, individual results will vary, this only works for one particular case, but it's still of interest how SAD works and affects each person.