Here's what to expect when clocks fall back.
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This Sunday, the U.S. is scheduled to set the clocks back – leaving us with an additional hour of daylight in the early morning, and one hour fewer in the afternoon. It marks the end of daylight saving time, (DST) which began in March.
Shifting our schedules ahead by one hour, as we do in the spring, can mess with our circadian rhythm, a cycle of hormone release and other bodily processes tied to cycles of light and dark.
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There's more light in the afternoon, and less in the morning, creating a mismatch between our internal clocks that follow that light and the social clocks that run our lives.
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When we set the clocks back in the fall, we get to do an entire hour of sleep all over again, in theory.
A 2013 review paper notes that there is "little evidence" that people actually get more sleep that night.
The review points to a 2010 study analyzing the sleep patterns of 88 people five days before and five days after the clocks shifted back one hour.
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A 2012 study of 120 people found that short sleepers, people who slept less than 7.5 hours, actually got about 20 more minutes of sleep in the days following the autumn time change. But that sleep tended to be heavily disrupted.
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A 2016 study found that the number of people diagnosed with seasonal depression in Denmark increased 11 percent right after the clocks are set back, and dissipated in the weeks following.
The study's author, Søren D. Østergaard at Aarhus University Hospital said he was "relatively sure" it was the transition into standard time that caused the uptick.
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"The transition to standard time is likely to be associated with a negative psychological effect as it very clearly marks the coming of a period of long, dark, and cold days."
In a 2008 study on 50 people, scientists found that our circadian rhythms tend to align with dawn under standard time (the time we will enter this Sunday).
But when DST was enacted in the spring, some people's internal clocks never fully adjusted.
It's also important to note that other experts suggest that it is possible to adjust to the time change.
This is why some scientists argue that it's time to do away with time changes for good.