A reader asks:

 We paraphrase here an important question posed by email, which was accidentally erased: “A popular light box manufacturer asserts that blue light apparatuses are effective for treatment of SAD, and represent a major step forward in the technology compared to standard white light apparatuses. This seems counter to CET’s advice that blue light apparatuses show no advantage. Please clarify.”


Blue vs. White Light: Mixed Results

First, there have been no published clinical trials showing that blue light is specifically antidepressant. On the other hand, there have been several basic research studies showing that by restricting light to the short-wavelength blue region, circadian rhythm resetting and melatonin hormone suppression can be achieved with lower total light energy than when using white light. Light wavelengths outside the blue region also trigger the circadian system and suppress melatonin, however. Indeed, by definition, white light contains blue. The balance of blue with other wavelengths in white light has repeatedly been demonstrated to be safe, effective and visually comfortable.

Blue Light Warnings

Blue light sources, especially when they are small, can cause extreme aversive glare. When they are placed near the eyes, as the vendor recommends, they can be intolerable. When placed at a “comfortable” distance, the eye does not receive the full-field illumination that is optimal for antidepressant treatment. There are also unresolved issues of safety. Blue light – like ultraviolet light – can cause a photosensitizing reaction in combination with several prescription drugs, thus harming the retina. The hazard of repeated exposure to blue light in therapeutic combinations is still a matter for investigation. In our opinion, it is premature, irresponsible and exploitative at this point to market blue light devices to people suffering depressive illness.