As evening darkened to night a few weeks ago, signifying the end of a wonderful but nearly sleepless weekend, I began to feel not only my eyelids, but also my mood getting heavy. As far as I could tell, there was no obvious reason for my crankiness other than my sleep deprivation attributed to a couple of early morning flights and a busy few days.
I remember returning from sleepovers when I was little and my parents telling me that I was cranky, but at the time I attributed it to something other than fatigue (something more along the lines of Mom and Dad were being just plain mean). But I’ve noticed my temperament changing when I’ve gotten fewer than the necessary hours of shut-eye. I started to ask myself if lack of sleep could actually be making me grumpy.
To my surprise, 60 Minutes reran a piece last night that focused on that very issue. Researchers like Matthew Walker at the University of California, Berkeley found that people who don’t get necessary 7.5 to 8 hours of sleep a night have more violent mood swings than those who get that amount of sleep.
Walker found this when he and his team deprived voluntary subjects of sleep and then showed them violent images while they were in a machine that shows brain activity. They found that one area of the brain is more active when someone has gotten less sleep.
“In the sleep-deprived subjects, Walker discovered a disconnect between that over-reacting amygdala (a region of the brain) and the brain's frontal lobe, the region that controls rational thought and decision-making, meaning that the subjects' emotional responses were not being kept in check by the more logical seat of reasoning. It's a problem also found in people with psychiatric disorders,” explained t.v. journalist Lesley Stahl.
So sleep plays an important role in moderating emotional reactions. These findings could even alter treatments for people with psychiatric disorders.
There are several other important reasons to get 8 hours of sleep a night (sleep helps moderate metabolism and improves memory), which scientists are only now beginning to understand.
I used to argue that people can get used to less sleep, but that also turns out to be incorrect. It seems that people now are proud of how little sleep they get, scientists in the story admitted. Based on an American Cancer Society survey of one million Americans, people in this country get an average of 6.7 hours of sleep a night, down 15 percent from just 50 years ago. Yet less is not more in this case: sleep remains a valuable and necessary part of life, say the researchers.
Although I don’t always spend a third of my day (or night) in bed, my mood may depend on just that. So apparently your prescription was right again, Mom and Dad. To avoid being cranky after a late night, I should just take a nap.