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Changes in Daylight Savings Time Influence Aggression

Changes in Daylight Savings Time Influence Aggression

While many people greatly anticipate gaining an extra hour sleep when Daylight Saving Time officially ends, new research finds that time changes may be accompanied by increased acts of aggression.

Intuitively, becoming more aggressive after losing an hour of sleep (which happens in the Spring) could be rationalized. However, researchers discovered increased acts of aggression actually happen in the Fall when we gain extra snooze time, and then lessen in the Spring.

Experts note that much has been studied about long-term effects of sleep deprivation. For instance, work by University of Pennsylvania’s Adrian Raine, a Professor of Criminology, Psychiatry, and Psychology, connected daytime drowsiness at age 15 to violence at age 24.

In a new study, fourth-year criminology doctoral student Rebecca Umbach wanted to better understand what happens immediately following sleep loss in the short term.

Working with Raine and criminologist Greg Ridgeway, Umbach hypothesized that after a night with an hour less sleep —
like what happens the Monday starting DST in the Spring — people would become more antagonistic.

“In the spring, the day after we move into Daylight Saving Time, there are more car accidents, greater stock market losses, more workplace injury, reduced test scores, and higher suicide rates,” Ridgeway says.

Their research, however, told a different story: On Mondays after the start of DST, the overall assault rate dropped by about three percent, findings the researchers published in the Journal of Experimental Criminology.

Investigators then looked at the fall time change, when we regain that hour of sleep. To their surprise, they found that assaults rose by about three percent the next day — a mirror image of the spring findings. However, they say their supporting evidence here isn’t as robust.

“Sleep problems have previously been associated with increased antisocial and criminal behavior, so we were surprised to find that increased sleep was associated with increased offending,” Raine says.

“This discrepancy is likely due to the fact that 40 to 60 minutes of lost sleep in one night is just not the same as months, or even years, of poor sleep.”

Regardless, the researchers say it is challenging to explain why these results occurred. Umbach surmises it may relate to internal biases.

“You think, ‘If I don’t get a lot of sleep, I’m going to be cranky and angry.’ You assume that’s the way you would react,” she says.

“Your intention is to act more aggressively, but your behavior does not reflect that because you’re tired. You’re too lethargic and sleepy to act.”

Daylight Saving Time made for a logical study subject. For one, research has shown that we tend to lose sleep because of the time switch, as opposed to anticipating the shift and going to bed early.

Secondly, nearly any other Monday of the year could, in theory, act as a control; to isolate sleep as the explanatory variable — rather than changes in weather or daylight, say — the Penn researchers chose the Monday the week after each time switch.

Finally, a large database called the National Incident-Based Reporting System tracks the time, date, and details of individual crimes for many cities across the country. The researchers supplemented this with data from New York, Chicago, Los Angeles, and Philadelphia.

Though the researchers don’t currently have plans for follow-up, Raine says anyone who ignores the morning alarm ring might take heed.

“Before we hit that snooze button, perhaps we should stop and think,” he says. “Hit the button and we might end up at least a little grumpier at work, and possibly more aggressive.”

Source: University of Pennsylvania/EurekAlert

Changes in Daylight Savings Time Influence Aggression

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2018). Changes in Daylight Savings Time Influence Aggression. Psych Central. Retrieved on December 3, 2020, from
Scientifically Reviewed
Last updated: 8 Aug 2018 (Originally: 27 Oct 2017)
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
Published on Psych All rights reserved.