A reader asks:

 What is your opinion about the safety and efficacy of green light boxes? A manufacturer cites some research to support the claim that these are as effective as the more commonly used white light therapy devices, but are much safer for the user’s eyes.


There are certainly no definitive data to support these claims. Professional consensus remains that bright white fluorescent light boxes are the clinical standard. They have been thoroughly tested in multiple, independent clinical trials and their safety (barring UV and excessive blue light emission) has been documented in long-term studies. White light contains elements throughout the color spectrum, including green. The inclusion of a small amount of blue light in white light is thought to enhance circadian rhythm phase shifting, which may be an element of antidepressant action. Green light exposure needs to be greatly intensified in order to match the phase shifting efficacy of small amounts of blue. How the various spectral components contribute to the antidepressant effect is still unknown. Ergo: don’t jump on an isolated spectral component and expect it to perform equally or better (or to be safer) than white light