When using bright light or light therapy devices for treating SAD full spectrum lighting is not only critical it is much more effective. Our eyes see definition and color through the lighting environment we are placed in.
Night time vision is made effective by the use of wider "rods" in the eye and views the environment monochromatically, or in gray scale. At night color is seen only in shades of black or gray. So at night time the quality of light is not as important.
Daytime vision is made effective by the use of narrow "cones" in the eyes. We see objects as light is reflected off of each object. The brighter the light the more we can see. The more we can see the greater the requirement for clarity and contrast. This is done by the superior quality of full spectrum light. Full spectrum lighting duplicates the visible wavelengths of sunlight at noon and uses both high clarity and balanced color phosphors.
When we suffer from seasonal affective disorder (SAD) or winter depression we are missing the exposure to natural light that we enjoy with the longer days of summer time. The closest thing to natural daylight is full spectrum lighting. Countless schools, businesses and homes have used full spectrum light to help with many problems associated with the lack of sunlight we experience in the winter. Full spectrum light also significantly reduces any chance of side effects that can be associated with the use of a poor quality light that is used in many light therapy devices. The lights we use do not produce "Ultra Violet Rays" in any wave length. Many companies that make light boxes know very little about lighting and make claims that are not consistent with their own statements. If the company that you are looking at states that the bulbs they use can be purchased through normal electrical supply or lighting supply houses their bulbs are not full spectrum.
A lot of companies talk about Kelvin temp but will not state the CRI because they use poor quality lamps in their lighting products. Ask for the specs in writing. If the lighting device does not use a light source of 90CRI or higher and Kelvin temp of 5000 to 6000 it is not full spectrum lighting. We will be glad to test any bulb you send us for free. Just send the bulb marked "Submit for Testing" to the PO Box 1087 Jackson, MI 49204 and we will test them at no charge in our spectrometer.