My contribution to anecdata is this:<p>Parents bought me a 180W fluorescent (therefore 10800 to 18000 Lumens according to <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Luminous_efficacy#Examples_2" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Luminous_efficacy#Examples_2</a> ) anti-SAD lamp.<p>Stupidly, I used it as an evening lamp instead of anti-SAD.  I had serious troubles getting to sleep for an entire year.  Typically took 1-3 hours.  Blamed coffee, stress, etc.  Got blackout curtains, earplugs, cooled room temp, reduced coffee, etc.  When I made the connection b&#x2F;t falling asleep and the anti-SAD lamp, I stopped using it altogether and almost instantly started falling asleep rapidly.<p>So I conclude my 10k-18k lumen lamp stimulated my awake cycle by about 1-3 hours.  My suggestion therefore is: use the lamp at either end of the day in winter: just before sunrise and just after sunset.  And certainly to shut it off 3 hours before bedtime.  In practice this is tricky because the &quot;unwanted dark hours&quot; are 4:30pm to 7:30pm which is: at work, my commute home and first hour at home.  So I need three lights, including one in the car?!