by Richard L. Hansler, Ph.D.
(Director, Lighting Innovations Institute, John Carroll University.
Executive Director, Light and Health Foundation.)
Originally published January 2007
The broadly accepted method of treating Seasonally Affective Disorder (SAD) is exposure to light in the early morning. The mechanism by which this improves mood is not well understood despite many studies.
There is some agreement that SAD is a manifestation of a delayed sleep phase syndrome. Lewy1 et al describes the evidence for a circadian basis for winter depression, in which he is able to advance the dim light melatonin onset (DLMO) by about an hour. It is generally agreed that DLMO is the most reliable measure of circadian clock setting. He does this by administering melatonin in the late afternoon. As a result there is a significant improvement in morning mood in 35% of the patients.
Burgess2 et al describe a weak correlation between mood and phase advance produced by exposure to morning light. Burgess3 demonstrated an advance in the DLMO of more than an hour in three days in preparation for an eastward flight. She did this by advancing sleep schedule by one or two hours a night with exposure to bright light in the morning. The two hour advance in sleep schedule advance DLMO slightly more (1.9 vs. 1.4 hours).
Klerman4 et al found that blind people and sighted people have the same duration of melatonin flow ( 9-11 hours) if the sighted people are kept in darkness.
Kayumov5 et al found that, by wearing glasses that block blue light at wavelength less than 530nm, subjects could continue producing melatonin during the night, even though exposed to bright light. This is based on the studies by Brainard6 et al and Skene7 et al, both of which showed that the action spectrum for melatonin suppression peaked in the blue at about 470nm.
Anecdotal evidence, as well as Kayumov’s experiment, support the belief that blocking melatonin-suppressing light is the equivalent of going into darkness as far as the pineal gland that produces melatonin is concerned. Putting on blue-blocking glasses several hours before bed time for a number of days in succession appears to advance the circadian clock, making sleep come quickly at bedtime. Because the melatonin flow is of limited duration (not more than 12 hours) it suggests that advancing the circadian cycle so that melatonin flow stops before wakeup time, will accomplish the same result as morning light treatment. Wu8 et al describe photochemical actions that may occur when blue light impinges on the retina that may result in macular degeneration. [See also “Artificial Lighting and the Blue Light Hazard” on this site.] For this reason it seems logical to try using blue blocking glasses in the evening to advance the circadian cycle, rather than blue light in the morning.
Using blue-blocking glasses in the hours before bedtime have the following advantages over the use of melatonin pills or bright light therapy.
1. The circadian cycle may be advanced as much as necessary to relieve morning depression by simply putting on the glasses earlier in the evening. The advance caused by melatonin or morning light is limited.
2. Using the glasses in the evening does not interfere with doing normal evening activities, such as working on a computer, reading or watching television. Morning light treatment requires a limitation on activities.
3. In addition to helping reduce morning depression, the glasses have been shown to promote better sleep for many people. Having melatonin present at bedtime allows people to fall asleep more quickly and sleep more soundly.
4. Research has suggested a potential risk of retinal damage from bright light (i.e. blue light) therapy. This method offers a safer and less expensive option.
5. In addition to being a sleep promoting hormone, melatonin is also a cancer fighting hormone. Maximizing the duration of melatonin is thought to explain at least part of the reason that primitive societies without artificial lighting have a much lower cancer rate. Studies by Blask9 et al support this belief.
6. Using the glasses in the evening can be combined with brief use of ordinary morning light (such as might be found in a cheerfully bright kitchen) to treat both the physical and psychological causes of the winter blues.
About the author
Dr. Hansler spent 42 years developing new and brighter light bulbs for GE Lighting at the world famous Nela Park in Cleveland, Ohio. Since his retirement from GE, he and his colleagues at John Carroll University have devoted their efforts to learning more about the effect of light on health. Blue blocking glasses have been successfully used to treat insomnia and show promise for people with bipolar disorder and SAD. For products designed to protect the eyes from blue light exposure, visit www.lowbluelights.com
1 Lewy AJ, Lefler BJ, Emens JS, Bauer VK. The circadian basis of winter depression. (Proc Natl Acad Sci U S A. 2006 May 9;103(19):7414-9. Epub 2006 Apr 28.)
2 Burgess HJ, Fogg LF, Young MA, Eastman CI. Bright light therapy for winter depression–is phase advancing beneficial? (Chronobiol Int. 2004 Jul;21(4-5):759-75.)
3 Eastman CI, Gazda CJ, Burgess HJ, Crowley SJ, Fogg LF. Advancing circadian rhythms before eastward flight: a strategy to prevent or reduce jet lag.
(Sleep. 2005 Jan 1;28(1):33-44.)
4 Klerman EB, Zeitzer JM, Duffy JF, Khalsa SB, Czeisler CA. Absence of an increase in the duration of the circadian melatonin secretory episode in totally blind human subjects. (J Clin Endocrinol Metab. 2001 Jul;86(7):3166-70.)
5 Kayumov L, Casper RF, Hawa RJ, Perelman B, Chung SA, Sokalsky S, Shapiro CM. Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work. (J Clin Endocrinol Metab. 2005 May;90(5):2755-61. Epub 2005 Feb 15. )
6 Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, Gerner E, Rollag MD. Action spectrum for melatonin reg ulation in humans: evidence for a novel circadian photoreceptor. (J Neurosci. 2001 Aug 15;21(16):6405-12.)
7 Thapan K, Arendt J, Skene DJ. An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans. (J Physiol. 2001 Aug 15;535(Pt 1):261-7.)
8 Wu J, Seregard S, Algvere PV. Photochemical damage of the retina. (Surv Ophthalmol. 2006 Sep-Oct;51(5):461-81. Review.)
9 Blask DE, Brainard GC, Dauchy RT, Hanifin JP, Davidson LK, Krause JA, Sauer LA, Rivera-Bermudez MA, Dubocovich ML, Jasser SA, Lynch DT, Rollag MD, Zalatan F. Melatonin-depleted blood from premenopausal women exposed to light at night stimulates growth of human breast cancer xenografts in nude rats. (Cancer Res. 2005 Dec 1;65(23):11174-84.)