Since I live in Alaska, I can tell you a good bit about S.A.D.
It affects all of us here badly in the winter. You crave carbs, you are always tired, etc. etc. The nurse at the clinic recommends that you get alot of vitamin D in your diets in the wintertime. Milk, cheese, etc.
Where I am located, it is almost always overcast with no sun and rainy most of the year, so it affects us here even more so.
It's as if you wish to hibernate. That's how it feels I can't tell you how much in the past month, I have taken several naps during the day and night because I can't stop being tired. And it's funny at the store, because everyone is buying lots of chocolate or candy. You can tell when it happens. And it does keep you from socializing to an extent because of the drop in energy that you get from it. But once spring rolls back around, all of us bounce back and have more energy than ever. That's why I kind of dread when winter gets here. I love the snow and I don't mind the reduced hours of daylight, but this S.A.D. thing drives me crazy. I hope that this information will help you.