A reader asks:

I was just wondering what your studies have shown on the application and effectiveness of broad vs. full- spectrum light box sources for bright light therapy solutions. From what I have read, it looks like full-spectrum might be the way to go as long as the light source is radiation- shielded and grounded. What do you think?


We moved away from use of full-spectrum light more than 10 years ago, and we recommend against it! Full-spectrum lamps do not produce antidepressant effects greater than broad spectrum lamps. At the high intensities used therapeutically, full-spectrum lamps boost unwanted short-wavelength radiation including unhealthful UV, which can cause immediate skin damage (redness, puffiness) in sensitive individuals and which pose a long-term cumulative hazard both to the skin and eyes. Furthermore, such lamps produce less total light per watt (that is, they are electrically inefficient) and are far more expensive than broad-spectrum alternatives. The light sources used in our clinical trials screen out UV radiation and are far more comfortable for treatment at high intensity (10,000 lux).