Is the logic behind the light box vitamin D or some other attribute about light?

I was prescribed a high dose vitamin D supplement (by my endocrinologist, not pdoc) to boost my energy. I can't tell you if it works because my psych meds kill my energy to the point where I'll be out by 10pm, which is early for me anyway. I used to not be able to fall asleep before midnight when I was in school even if I hadn't sleep more than a few hours in days. Now if I make it past 11pm, I'm lucky regardless of how much I slept the night before.

Also, sometimes we're achey and tired for no reason. It just happens.