I participated in this study, with full-room illumination of 60.000 lumens and 6 hours per day of treatment. The effect was remarkable. Throughout Winter 2019/2020, I did not feel depressed or lethargic on even one single day on which I used the setup correctly. I did feel depressed 2-3 times per week in the weeks prior to starting treatment. And I felt depressed on some of the days where I did not use the system.

Here's what surprised me: Throughout the winter I went hiking in direct sunlight for 3 hours each day. And my office had really big windows with unobstructed view of the Sky. And that still wasn't enough to fix depression. By adding 6h of light therapy per day on top of that, my winter depression vanished.

I am amazed that such a simple, cheap and side-effect-free intervention has such a big effect. On top of that, such whole-room illumination is really pleasant subjectively and makes me feel as if I'm sitting outside. When friends suffer from SAD, light therapy is the first thing recommend.

Woo! Congratulations.

I just thought I'd return here a few months later to add an update for people who may be considering building their own lamp.

Having built my own lamp with 6000K LEDs that are not designed specifically for SAD treatment, I have found that it does tan my skin and create a feeling of sensitivity.

On doing some research, it seems that purpose-built SAD lamps filter out the UV part of the spectrum.

This seems like an important consideration for anyone who may be planning on building their own.

For my own filter, I am considering buying some UV blocking film! Hopefully this will solve the problem.

I experimented with using a very powerful halogen bulb (double envelope for safety) positioned as close as possible to my face and it seemed to work quite well, it really did feel like a summer afternoon if I closed my eyes. It’s a remarkably simple thing to do too so developing a more convenient system would seem to be highly useful. 

You mentioned in the pre-print that results were "similar" for the two color temperatures, and referred to the Appendix for more information, but it seems like the Appendix isn't included in your pre-print. Are you able to elaborate on how similar results in these two conditions were? In my own personal exploration of this area I have put a lot of emphasis on color temperature. Your study makes me adjust down the importance of color temperature, although it would be good to get more information.