I have SAD in the late fall-winter seasons. Part of it is I really, really hate being cold, and the other part is I have to deal with months of gray skies and rain where I live. I don't do well when there's no sunlight to speak of. I have a Happy Light now which helps some, although it would probably work better if I got up way earlier than I do (I'm a night owl who goes to bed around 1 or 2 and gets up around 10) to sit in front of it.