that if you were born between November 1 and March 31 there is a much better chance that you would have SAD, fibro, MS or parkinson's.

The reason is not because of something you are doing, but because depending on the circumstances, your mother was probably vit D deficient while carrying you.

This really adds up for me: not just because I was born between those times, but when looking at my daughters. Both were born in November. Both have SAD, but the younger one is much, much worse and she even has symptoms of CFS. I was living in Vermont while I was carrying her, but still in Virginia when carrying the older one. There were days when I couldn't even go outside up there. My son, who was born in April, so far has exhibited no signs of SAD.