The Dark Side of Daylight-Saving Time

Content provided by:

The 2007 shift of daylight-saving time from the first Sunday in April to the second Sunday in March seemed like a great idea. After a long, dark winter, who wouldn't want an extra hour of daylight in the evening?

For starters, anyone who has trouble waking up in the dark. After all, we only gain an hour of daylight in the evening by losing an hour of daylight in the morning. So despite the lengthening days of spring, many people will now find themselves forced to wake up in the dark instead of in the light for much of March.

This darker side of daylight-saving time has some doctors and researchers concerned about the impact the earlier time change will have on people with winter depression. That's because there is a growing body of research showing that dark mornings—not short days—are the real trigger for seasonal affective disorder, a form of clinical depression that occurs cyclically every winter.

"People who suffer from SAD and milder forms of winter depression rely on the morning light to assist with waking up and to synchronize their circadian rhythms," says Dr. David Avery, an associate professor of psychiatry at the University of Washington School of Medicine. "We now know that the lack of morning light that's typical in the wintertime is the main cause of winter depression."

Adds Dr. Alfred Lewy, a professor of biological psychiatry at Oregon Health & Science University: "For those with winter depression, moving the clocks ahead in March could cause a temporary stalling or setback in the natural remission of symptoms that typically starts around this time."

Who's at risk?

The further north you live, the more at risk you are from the negative impacts of moving daylight savings time to March. That's because rates of SAD and less severe forms of winter depression increase as one moves further north.

"Epidemiological studies have shown that the rate of full-blown SAD is around 1 percent in Florida, 4 percent in [Washington] D.C., 5 percent in New York and 10 percent in New Hampshire and Alaska," says Avery. "Rates of less severe winter depression also increase as one moves north."

Also more at risk are those living in the western edge of a time zone, where sunrise is already late to begin with. Take, for instance, Newark, N.J., and Indianapolis, two cities at similar latitudes with similar day lengths. Although both are in the Eastern time zone, sunrise in Newark was around 7:15 a.m. on Sunday, March 9 while the sun didn't rise in Indianapolis until after 8:00 a.m.

The later the sunrise, the greater the chance that you will have to wake up in the dark—something that many people find unpleasant, and some may find it downright depressing.

What to do?

For those who suffer from any form of winter depression, the most important thing to do is to continue your standard treatment throughout March.

If you're lucky enough to have some control over your daily schedule, another trick you can try is adjusting your wake time based on the time of sunrise and your own personal body rhythms rather than adjusting to the time on the electronic clock.

That's essentially what Lewy had some SAD patients do in a small pilot study. The result: Within just a few days of adjusting their sleep schedules to the sun and their natural rhythms, their symptoms of seasonal depression quickly reversed.

Lewy said he didn't continue the study because it didn't seem like a practical solution for most people.

More importantly, adjusting your sleep schedule to the sun only makes sense if you can do it seven days a week. If you can't avoid waking up to an alarm clock in the dark on weekdays, you're actually doing yourself more harm than good by sleeping in on the weekend.

“Staying up late and sleeping in on the weekends creates a mini jet-lag every weekend—it’s like flying from Seattle to Honolulu on Friday night and then trying to fly from Honolulu back to Seattle on Sunday night," says Avery. "You definitely pay for it on Monday morning.”

Morning person or night owl?

Are you happy about early daylight-saving time or unhappy about having to get up in the dark in the morning? Join the discussion on our message boards.

More on Seasonal Affective Disorder:

Lisa Farino is a Seattle-based health and science writer and a board member of the Northwest Science Writers Association. She is a regular contributor to MSN Health & Fitness.