Enter, darkness

(Jon Krause For The Washington Post)
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By Leslie Tamura
Tuesday, November 16, 2010

The weather is getting gray and cold, and that summer sense of excitement has melted away. It's dim dark in the morning when you get up and dark in the evening when you come home. And it's all making you feel downright blah, maybe even teetering on depressed.

Sounds like the wintertime blues.

"It doesn't necessarily mean you're sad or down, you're just lacking in the push that all people need to get through the day," said Norman Rosenthal, a Maryland psychiatrist who studies seasonal conditions such as the winter blues. In the mid-1980s, Rosenthal and his colleagues at the National Institute of Mental Health coined the term "seasonal affective disorder," or SAD, for an extreme form of the wintertime blues.

About 20 percent of Americans start to feel down as the days get noticeably shorter, Rosenthal said. Some people start feeling their mood change as early as July, when daylight begins to grow shorter after the summer solstice on June 21. Most, however, first notice the change after they move their clocks back into standard time, which this year occurred on Nov. 7 . It's a little lighter in the early morning for a few weeks until the days shorten even more, but it's nearly nighttime for the post-work commute home.

Psychiatrists and chronobiologists - scientists who study organisms' internal rhythms - say exposure to light, morning light in particular, is what makes the difference to mood.

"Light during the middle of the day is of no consequence," said Alfred Lewy, a psychiatry professor at Oregon Health & Science University who studies SAD.

Rosenthal, who wrote the book "Winter Blues," agrees that morning light has been shown to relieve the blues, but he adds that light can be helpful at any time. "Light can have an immediate boosting effect on energy and mood," Rosenthal said. "We don't really know why morning light works."

During winter, the sun rises later in the day and does not stick around for very long - especially the farther you are from the equator. During December in Miami, for instance, the sun is up for about 11 hours, while in Washington it's a little more than nine hours, which means nearly 15 hours of darkness.

The role of light seems apparent when you consider some geographical differences in the winter blues. According to Rosenthal, about 3 percent of Floridians report having the blues, while in Maryland, the number rises to 10 percent. In Fairbanks, Alaska - where the sun is up for only about four hours in December - it's about 19 percent.

Regardless of location and for reasons that are unclear, women are three times as likely as men to develop the seasonal symptoms, says Rosenthal.

The waning light

Why might the waning light cause lethargy, depression, social withdrawal and even hunger in many people?

Some scientists suggest that those who experience the winter blues are just more sensitive to light and light deprivation. Others have shown that, in people with the blues, serotonin, the brain chemical involved in feeling satisfied, dips excessively when there is less daylight.

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