Bright Light Treatment Research

THE BASICS About Bright Light Treatment Research

A lot is known about bright light treatment and light therapy research; it involves the use of a special type of light fixture that produces much brighter light than regular indoor lighting. The intensity of the light is given in lux. Lux is measured at a specific distance away from a light source; for light therapy devices, this specific distance is at the user's eyes. Because light diminishes with distance, light box intensity ratings should always be given at a specific distance from the unit.

Light Therapy Research

Lux is not the same as lumens. Lumens refer to the amount of light generated by a bulb at its surface. Since light intensity decreases exponentially with distance from the light source, knowing the number of lumens a light bulb gives off doesn't help you in determining at what distance you'll receive a particular amount of lux, especially since other factors– such as the positioning of the bulbs in relation to each other within the fixture, whether it is covered by any kind of diffuser, and the reflectivity of the surface behind the bulbs– can affect the light output of any fixture.

Bright light treatment requires a minimum of 2,500 lux to be effective, and the brightness recommended by researchers and clinicians for most people is 10,000 lux – an amount significantly higher than standard indoor lighting.1 Most homes have light levels between 100-300 lux, while well-lit offices generally don't go above 700 lux. While daylight is almost always at least 10,000 lux (on a clear spring morning, around 10,000 lux; at noon in the height of summer, over 100,000 lux), natural sunlight levels are often unpredictable due to weather, latitude or terrain, and may not be available at the times required (either early morning or evening).2 Therefore, the purchase of an appropriate device is recommended for those undergoing bright light treatment.3

WHAT IS AN APPROPRIATE LIGHT BOX?

The best lights for bright light therapy are fixtures containing white fluorescent light bulbs behind a diffuser, and tilted forward so that the light is angled downward, permitting more light to enter the eyes and decreasing the apparent brightness of the light, in turn creating less glare and improving user comfort.4 The diffuser performs two purposes: it spreads the light evenly over the surface of the unit, and it absorbs and filters out the potentially harmful UV rays.5 A variety of light boxes are available to meet individual needs, including large models on floor stands for use with exercise equipment, very compact models for frequent travel, and even models designed to fit into standard office decor.

While the critical factor in bright light treatment with a light box is the intensity of the light, full spectrum light with the UV-A and UV-B filtered out for eye and skin safety produces less glare than other types of lighting, resulting in greater user comfort.6, 7, 8, 9

What about BLUE LIGHT

Dr. Norman Rosenthal in his 2008 revision of "Winter Blues" writes: "From my point of view, however, a lot more testing is needed before we can conclude that blue light is safe and effective, let alone superior to white light. Remember we now have over twenty years of experience with white light, which is both safe and effective. I therefore recommend traditional white light-not blue light-for the treatment of SAD."

LIGHT VISORS

A newer technology is the head-mounted Light Visor, which allows the user more freedom of movement while receiving bright light treatment.

The Visor's efficacy rate among patients with Seasonal Affective Disorder [see Seasonal Affective Disorder (SAD) & Winter Blues section] is comparable to that of light boxes. However, research has yet to determine whether it is an active treatment or whether it acts as an elaborate placebo.10

Until clinical studies determine the outcome of this issue, the consensus among researchers is that for most people, except those for whom the ability to move around during treatment is extremely important, a light box is probably a better choice than a Light Visor. "The fluorescent light box is the 'gold standard' device for light therapy."11

DAWN SIMULATION

There is much interest at the present time in dawn simulation as a treatment. Dawn simulation involves gradually increasing the light level in the user's bedroom shortly before awakening. Since it occurs while the user is asleep, it does not require a special amount of time to be set aside for its use, making it much more convenient than traditional light therapy. It uses standard indoor light levels, not the high intensities used in bright light treatment.

Preliminary studies on dawn simulation are promising, with response rates similar to those of bright light treatment with a light box, but researchers caution that more research is needed to show whether it is indeed as effective as bright light treatment.12, 13, 14, 15, 16, 17

SIDE EFFECTS

Bright light treatment is generally well tolerated by most people. Side effects, when they do occur, are almost always transient and mild, and only a very small percentage of people who try bright light treatment need to discontinue it due to troublesome side effects.18

For those who experience initial side effects, there are two easy ways to reduce them while allowing your body to acclimate to the light therapy: either move a few inches further away from the light source and gradually, over several days to two weeks, move closer until you are at the correct distance to receive 10,000 lux of light, or reduce your treatment time (to 15 minutes instead of 20-30 per day) initially, and gradually increase your exposure time by a few minutes every few days until you are using it for the amount of time your body requires.19

In the several published clinical studies that examined side effects, the most commonly reported side effects were: headaches, eye strain, nausea, feeling 'wired', and dizziness.20, 21, 22, 23

SAFETY ISSUES

Bright light treatment with a properly constructed fluorescent light box is generally considered to be safe.24, 25, 26 Studies examining the effects of short-term (up to 4 weeks) and long-term (three to ten years) on the eye showed no changes in response to the use of the lights.27

It is well known that ultraviolet (UV) exposure causes damage to the eyes and skin. Numerous sources warn of the danger of excessive UV exposure from improperly constructed light boxes that do not eliminate the UV wavelengths. One of these sources cautions that UV levels in fluorescent light fixtures without appropriate diffusers to eliminate them could reach toxic levels in twenty years of daily use during the winter.28 Therefore, it is very important that any light device being used for bright light therapy be free of UV wavelengths. Any manufacturer that you consider purchasing a light box from should be able to provide independent laboratory verification that their light boxes are UV free.

While light treatment appears to be safe for most people, researchers warn that certain people should be carefully monitored when using light treatment. People who have preexisting eye abnormalities (for example, macular degeneration or retinitis pigmentosa), those with systemic illnesses that affect the retina (diabetes mellitus, systemic lupus erythematosis), those who have had cataract surgery, and those taking certain photosensitizing medications (including tetracyclines, sulfonamides, psoralens, and some antidepressants and neuroleptics) should begin light treatment only with routine ophthalmologic examinations and with careful consideration of the risks and benefits.29, 30

1 Rosenthal, NE: Winter Blues: Seasonal Affective Disorder - What It Is and How to Overcome It. (rev. ed.) New York: Guilford Press, 1998, p 239.
2 ibid, pp 108 & 138-139.
3 Kripke, DF & RT Loving: Bringing therapy to light. Sleep Rev. Winter 2001.
4 Rosenthal, 1998, p 107.
5 ibid, p 108.
6 ibid, pp 108, 110 & 117.
7 Berman, SM & DL Jewett: Full vision photometry for the computer workplace based on physiological and behavioral principles. Conference Paper presented at a symposium of the CIE (International Commission on Illumination). Undated.
8 Berman, S: The coming revolution in lighting practice. Energy User News. 25(10), 2000.
9 Brainard, GC, NE Rosenthal, D Sherry et al.: Effects of different wavelengths in seasonal affective disorders. J Affect Disord. 20, pp 209-216, 1990.
10 Wesson, VA: Light therapy for seasonal affective disorder. In: Seasonal Affective Disorder and Beyond: Light Treatment for SAD and Non-SAD Conditions. Edited by Lam, RW. Washington, DC: American Psychiatric Press, 1998, p 69.
11 Lam, RW & AJ Levitt (eds): Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder. Canada: Clinical & Academic Publishing, 1999, p 65.
12 ibid, pp 66-67.
13 Wesson, p 70.
14 Avery, DH, DN Eder, MA Bolte et al.: Dawn simulation and bright light in the treatment of SAD: a controlled study. Biol Psychiatr, 50, pp 205-216, 2001.
15 Avery, DH, MA Bolte, SR Dager et al.: Dawn simulation treatment of winter depression: a controlled study. Am J Psychiatry, 150(1), pp 113-117, 1993.
16 Norden, MJ & DH Avery: A controlled study of dawn simulation in subsyndromal winter depression. Acta Psychiatr Scand, 88, pp 67-71, 1993.
17 Terman, M, D Schlager, S Fairhurst et al.: Dawn and dusk simulation as a therapeutic intervention. Biol Psychiatr, 25, pp 966-970, 1989.
18 Wesson, p 70.
19 Rosenthal, p 119.
20 Lam, p 74.
21 Kogan, AO & PM Guilford: Side effects of short-term 10,000-lux light therapy. Am J Psychiatry, 155(2), pp 293-294, 1998.
22 Labbate, LA, B Lafer, A Thibault et al.: Side effects induced by bright light treatment for seasonal affective disorder. J Clin Psychiatr, 55(5), pp 189-191, 1994.
23 Levitt, AJ, RT Joffe, DE Moul et al.: Side effects of light therapy in seasonal affective disorder. J Clin Psychiatry, 150(4): pp 650-652, 1993.
24 Lam, p 74.
25 Rosenthal, p 122.
26 Gallin, PF, M Terman, CE Remé et al.: Ophthalmologic examination of patients with seasonal affective disorder, before and after bright light therapy. Am J Ophthalmol, 119, pp 202-210, 1995.
27 ibid.
28 Lam, p 73.
29 ibid.
30 Remé, CE, C Grimm, F Hafezi et al.: Lamp standards and ocular safety. In: Seasonal Affective Disorder. Practice and Research. Edited by Partonen, T & A Magnusson. New York: Oxford University Press, 2001, pp 79-83.