And what about colored light? White is so-o-o boring! Color therapies — even taking a bath in colored light! — have long been staples of the untested, commercialized, and widely debunked armamentarium of “alternative healing.” There was an early claim that wearing rose-colored glasses could relieve SAD. Others maintained that invisible ultraviolet light close to visible blue was especially beneficial, even though it is patently dangerous and can lead to tanning addiction. One company promoted green light, based on the hypothesis that the antidepressant effect is maximal when the retinal receptors for sensory effect — vision — are selectively stimulated. We have learned since, however, that antidepressant effect is not exclusive to green.

Not that color is irrelevant. Recent lab research has convincingly demonstrated that light at the short-wavelength end of the visual spectrum — corresponding to violet, indigo, and blue — does have a selective effect on the circadian timing system, especially with long exposures. This is one good reason to cut down on exposure to these wavelengths during the evening hours — a point we discuss in Chapter 5, “Getting Light Wrong,” of our book, Reset Your Inner Clock. 

To Market, To Market We Go!  Put a light therapy device on the market that features blue or bluish light, and you have a toutable difference from your competitors.  Unfortunately for this business plan, blue light devices provide no clinical benefit over well-tested white light boxes. There are also concerns about safety and efficacy, as well as visual comfort. Irradiation of the retina with blue light can interact with several common medications, and there are cautions especially for people 50 and above who have, or who are at risk for, macular degeneration.  Despite the contrary claims of lighting engineers, the continual use of blue light devices may have adverse biological consequences. These may take decades to build up, so they would not be evident with short-term testing.