Vitamin D appears to be at least tangentially related. A bunch of other studies show most people are low on Vitamin D, so it's worth paying attention to, regardless.
As far as lighting goes, the relevant factors appear to be 10,000 lumens (at whatever distance makes that happen). What I found didn't clarify well on light - maybe natural spectrum, maybe specifically blue. It appears to help if the light comes from at or above eye level, and you have to be awake/open-eyed, but don't have to look directly into the lamp. Time seems to vary from 15-20 min to 30-45.
It looks like most lamps advertised for SAD don't actually have enough lumens to be useful - they mostly focus on being full spectrum. The ones that do mostly look pretty expensive, around $200. I did see one which was only ~$100 now with useless "ion therapy".
I looked at several Ask Metafilter links, but they're mostly pretty anecdotal.