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Living in perpetual twilight.

For most of the time, and for most of us, melatonin is the right substance at the right time, and gently manages to recede when wakefulness is required.

But for some who literally live in perpetual twilight -- because they do not get enough natural light -- its effects can be severely depressing. Such victims are the homebound and institutionalized. These individuals never stop producing melatonin because the organs that control its production never get an adequate signal to shut down.

Consequently, they are chronically sedated. The effect is similar to a patient taking tranquilizers 24 hours a day.

Another group consists of people who go to work early in the morning, spend all of their daylight hours in a windowless office or workplace, and return home late at night, having scarcely encountered direct sunlight, or any light at all along the way.

A third group consists of individuals whose melatonin levels are unexplainably high much of the time. As days grow shorter and their melatonin levels rise, these people gradually become sad, irritable, anxious, socially withdrawn, and uninterested in their work. Their need for sleep increases to the point where they become practically dysfunctional. Science recognizes this condition as Seasonal Affective Disorder (SAD), for which, fortunately, the administration of light therapy seems to be a practical remedy.

Current research cannot explain exactly how the process works. At a Portland, Oregon, clinic, Alfred Lewy, M.D., said that light makes the body believe morning has arrived and, under its influence, body functions shift rapidly midcircuit to appropriate levels. The sleep-wake cycle takes its cues from the others.

Another researcher, Fred Turek, Ph.D., commented: "Nobody knows how this works. We know the light goes into the retina; we know it travels to the suprachiasmatic nucleus. We know there are 8,000 neurons in that organ. But we don't now know what's going on in those cells."
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Title Annotation:The Tyranny of Time: Solving the Mystery of Our Inner Clockwork; melatonin's physiological affect on the body
Publication:Nutrition Health Review
Date:Jan 1, 1992
Previous Article:Millions can be saved from work hazards by light therapy: better than sleeping pills and drugs that usually worsen the condition.
Next Article:Oddities of circadian rhythms.

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