Everyone, I found an excellent article... it's an interview with Dr. Rosenthal. Please take a moment to skim this... I feel it will be incredibly helpful to a lot of people.
I still do feel strongly that if more research is done, they'll find that SAD (and possibly some other mood disorders) are caused by sleep problems and are not mood disorders. I respect that some will not agree, but if you're curious, please look at the following link to another discussion about new studies that point in that direction: