First introduced during World War I to make better use of the longer daylight available during summer and conserve energy, daylight saving time (DST) now operates in about 70 countries, including the United States. Twice a year, clocks shift, moving an hour forward in spring and back in fall. That single hour may not seem like much, but growing evidence suggests it can have significant effects on physical and mental health.
The spring transition is particularly harmful. Numerous studies across the U.S., Sweden, Croatia, Germany, Brazil, Finland, and Mexico have found a small but measurable increase in hospital admissions for heart attacks immediately after the clocks move forward, around 4%. Similar research has linked the small shift in time to higher rates of strokes in the weeks after and a 6% rise in fatal car accidents, largely attributed to people losing an hour of sleep. One 2020 study also connected DST to worsened mood disorders, depression, anxiety, and substance abuse.
Experts say the culprit is a disruption of the body’s circadian rhythm ? the internal clock that regulates sleep and wake cycles. Morning light resets this rhythm, while the rising melatonin levels in evening darkness signal it’s time to sleep. But when evenings stay bright, melatonin production is delayed, making it harder to fall asleep and leaving many people tired and out of sync. And the cumulative effect of fragmented sleep may affect heart rate, blood pressure, stress hormones, and metabolism. Even the clock change in the fall, though it offers an extra hour in bed, has downsides. Danish researchers reported an 11% increase in depressive episodes during the 10 weeks following the autumn shift.
Regardless of which time system offers the most advantage, most researchers agree that switching back and forth is the worst option for our health. They say maintaining one consistent time year-round would be better, with permanent standard time offering the greatest benefits because it aligns more closely with natural sunlight and the body’s biological rhythm.
Yesel Kang Copy Editor teen/1762915766/1613367750
1. What does the increase in anxiety or substance abuse after Daylight Saving Time reveal about its mental impact?
2. Which countries or regions have already abolished daylight saving time, and why?
3. Why might the autumn shift in daylight saving time still have negative effects on people’s health and mood, even though it technically gives them an extra hour of sleep?
4. What does research suggest about the cumulative effect of sleep disruption over time?
1. If daylight saving time was originally introduced to save energy, do you think it still serves that purpose today?
2. Why might some people enjoy longer daylight in the evening while others prefer earlier sunrises?
3. Which factors?like screen time, caffeine, or stress?make it harder for you to sleep well during DST transitions?
4. What strategies have you found most helpful for maintaining a healthy sleep routine all year round?
First introduced during World War I to make better use of the longer daylight available during summer and conserve energy, daylight saving time (DST) now operates in about 70 countries, including the United States. Twice a year, clocks shift, moving an hour forward in spring and back in fall. That single hour may not seem like much, but growing evidence suggests it can have significant effects on physical and mental health.
