OP here. I'll give a qualified yes.
It's hard to actually know which action I take has the most effect. Vitamin D, bright lights, exercise all play a role. I've found it's important to try everything and hope for the best.
If I were to pick just one thing to do though, it would be the bright lights in the morning. I know for sure that those work. Not only for myself, but for many other people who have given it a try.