I DO use one and feel they have dramatically affected me for the good. My depression is significantly less than normal for this time of year. That may be due to the light.

But I DO credit the light for improving my sleep pattern. I no longer sleep/nap throughout the day, sleep at appropriate times, and now sleep a very good 8-10hrs a day (I was sleeping 14hrs plus naps during the day).

The important thing is that you need to look for a light with a minimum of 10,000 lumens.

My psychiatrist and I researched a lot of lights and came up with several options. The cheapest I found (and bought) was the "LiteBook Advantage" retails 109cdn/89usd. The company makes a rechargable version for $169cdn. The best part I like about it is it's size. I can fit it in my purse. Another convenience is that it automatically turns off after 30min (I get so used to it I forget it's there). It is LED which makes it small and also less likely to burn out and won't require regular replacement of expensive bulbs.

Do NOT use a lamp in the afternoon as this can really screw up your rythm and sleep patter.