Seasonal Affective Disorder (SAD) is a common condition in Northern Latitudes like the Scandinavian countries and Alaska. It occurs most often in winter when there is little to no sunlight, even at noon. The condition has identical symptoms to depression and resolves when individuals are exposed to bright light (2,000 to 10,000 lux) for at least 30 minutes a day. This amount of brightness can be achieved indoors by being exposed to a special bright light (such as the Hap-E light)i or by being outdoors in the United States (at similar latitudes) at least 30 minutes after sun-up and at least 30 minutes before sundown. The only mandatory exposed human surface to the light is the eyes.
Outdoor light is amazingly more intense than the normal indoor variety. Outdoor light can reach 3000 lux on a bright sunny day.ii A bright indoor environment may provide only 400 lux, less than 15 percent of daylight brightness.iii Bright light, such as sunlight, increases serotonin production in the daytime, which can in turn treat depression and fatigue.iv Bright light exposure in the day may also increase blood melatonin levels at night, which can create more restful and efficient sleep.v
Bright light therapy can also help restore the normal daily body rhythm called the circadian rhythm. If a person has problems with early morning awakening (3 to 5 a.m.) but needs more sleep, exposure to bright light in the early evening for 30 minutes can restore the normal sleep pattern. For the more common problem of not being able to fall asleep at bedtime (insomnia), combine with awakening too late in the morning, exposure to early morning bright light (6 to 8 a.m.) can restore the normal sleep cycle.vi Utilizing morning-light therapies for depression bring superior results to evening-light therapy, although evening therapy is better than no light therapy at all.vii
I usually recommend an exercise program that is outdoors in the morning sun. This is not possible for everyone to do in winter when the sun comes up later. For these people I recommend a lunch time outdoor exercise period such as a brisk walk for 30 minutes. Others who are fortunate enough to have a south side office window that brightens their room enough that indoor light is unnecessary, can often get by without taking the afore-mentioned outdoor exercise precautions.
However, there is one additional important benefit of outdoor exercise to consider—negative ions. Fresh country air has negative ions that have been demonstrated to both treat and prevent depression.viii
i. M. Terman, "Light treatment," in M. H. Kryger, T. Roth, W. C. Dement (eds), Principles and practice of sleep medicine second edition (Philadelphia: WB Saunders Company, 1994): 286-300.
ii. R. J. Reiter, J. Robinson, "Back in Sync," melatonin: Your Body’s Natural Wonder Drug (New York, NY: Bantam Books): 161.
iii. Ibid.
iv. M. L. Rao, B. Muller-Oerlinghausen, et al., "The influence of photo-therapy on serotonin and melatonin in non-seasonal depression," Pharmacopsychiatry (May 1990): 155-158.
v. M. L. Laakso ML, T. Porkka-Heiskanen T, et al., "Twenty-four-hour patterns of pineal melatonin and pituitary and plasma prolactin in male rats under ‘natural’ and artificial lighting conditions," Neuroendocrinology (September 1988): 308-313.
vi. D. R. Wagner, "Sleep disorders; disorders of the circadian sleep-wake cycle," Neurologic Clinics (August 1996): 651.
vii. M. Terman, "A controlled trial of timed bright light and negative air ionization for treatment of winter depression," Arch Gen Psychiatry (October 1988): 875-882.
viii. Ibid.
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This article is adapted from the book Depression: The Way Out by Dr. Neil Nedley. Visit Dr. Nedley's website
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