HARTFORD, Conn. -- Come this weekend, we'll have an extra hour of sunlight in the evening. This sounds great, but researchers say that shifting our internal clocks twice a year might affect us adversely -- from more traffic accidents to lower SAT scores.
One worry about daylight saving time, which happens Sunday morning at 2 a.m., is sleep deprivation. When we spring forward, we lose one hour of sleep. That may not seem like much of a jolt, but studies suggest most of us don't get enough sleep as it is, so losing even an hour can take its toll.
The one-hour time shift also seems to wreak havoc with our circadian rhythms, the 24-hour cycle our bodies are accustomed to. The cycle sets itself according to sunrise and sunset.
Daylight saving time was adopted in the United States in 1918, long before the medical community began looking into seasonal affective disorder -- a feeling of depression and sluggishness that comes from the lack of exposure to sunlight.
Andrew Winokur, director of psychopharmacology at the University of Connecticut, said we thrive on consistent patterns.
"When there's a sudden change in that, we as humans can feel it," he said. "We get used to, and more comfortable, being on a specific pattern, and when that changes, we're more likely to feel out of sorts than better. I would say it's slightly analogous to jet lag."
Of particular concern to Paul Desan at Yale University is how little we know about the long-term effects of seasonal affective disorder.
"In my opinion, the research is not very complete and is contradictory," said Desan, a professor of psychiatry who specializes in seasonal affective disorder. "We're doing this vast public experiment without knowing what we're doing."
A few studies have looked at very specific effects of daylight saving.
A study published in the February issue of the Journal of Neuroscience, Psychology and Economics found that the biannual time shift caused a 16-point drop in SAT scores among high school students in Indiana.
Until 2006, some of the state's counties observed daylight saving and others didn't; the study compared the results from both. Co-author John Gaski, an associate professor of marketing at Notre Dame, said the results aren't connected to the one-hour loss or gain of sleep because the tests weren't taken close to either time shift. Rather, he believes they reflect the long-term effects on students' circadian rhythms.
"We thought if we got 2 points or 5 points, that that would be a blockbuster -- and we got 16 points," Gaski said. Based on how much research has been done on sunlight's effect on our mood, though, Gaski said it shouldn't be that surprising.
"Having clock time so much different from your natural bio-rhythms can't be good."
A Canadian study from the mid-1990s found that traffic accidents increased by 8 percent the day after clocks were pushed forward one hour in the spring. Accidents decreased by about the same amount when they were pushed back in the fall.
And in 2008, a study by Swedish researchers found that heart attacks decreased by 5 percent the day after the fall transition, presumably because of the extra hour of sleep. The bad news was that heart attacks increased by 6 percent in the three days after the spring transition.
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