Why Sunlight Is So Good For You

Even Hippocrates believed that the changing seasons had something to do with health—and that the key was how much available daylight there was during different times of the year.

Many centuries later, it's clear he was on to something. As people spend more time indoors staring at computer and television screens, scientists are starting to appreciate how exposure to sunlight affects various body systems.

The most interesting support for our dependence on daylight emerged with a condition called Seasonal Affective Disorder, or SAD. The term was coined by Dr. Normal Rosenthal at Georgetown University to describe the so-called winter blues: the lethargy and feelings of sadness and hopelessness that come when the weather forces people to spend more time indoors and the season provides little opportunity for exposure to natural light. Some people have speculated that our modern lifestyle, which keeps people indoors under artificial light for so many hours, may be encouraging a form of SAD year-round.

Rosenthal found that while not everyone is as strongly affected by a lack of sunlight, for the people who are, light boxes that blast a few minutes of bright light in the frequency of natural sunlight each morning can help to elevate mood and re-energize them to face the day.

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