Penn study: Assaults increase after end of Daylight Saving Time

Daylight Saving Time ends this weekend, which means you'll be more likely to assault somebody on Monday – or, perhaps worse, be assaulted – recent research from the University of Pennsylvania suggests.

On the Monday after Daylight Saving Time ends, when we gain an hour of sleep, the average assault rate is 2.8 percent higher than on the following Monday.

What's more, the study found that on the Monday after Daylight Saving Time starts, there were 2.9 percent fewer assaults compared to the following week.

Although the long-term effects of sleep deprivation are well-documented, doctoral student Rebecca Umbach conducted the research with professor Adrian Raine and associate professor Greg Ridgeway to find out more about the effects of short-term sleep loss.

Umbach seemed to draw her initial hypothesis from common sense. After all, wouldn't gaining an hour of sleep cause people to be better rested, less grumpy and therefore less likely to punch someone?

Not so, her research found.

"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 told Penn Current, a university news site. "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."

The research was based on data from the National Incident-Based Reporting System and city-reported data from Chicago, New York, Philadelphia and Los Angeles.

Researchers did indicate that the fall findings had less to do with Daylight Saving Time than those for the spring.

Speaking with The Current, Raine actually warned people against ignoring alarms or hitting the snooze button in general – things we tend to do from time to time.

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