The Science of Willpower

Secrets for self-control without suffering

In Defense of a Good Night's Sleep

Disrupt your sleep, disrupt your body and brain.

It's so tempting to cut back on sleep when you can't figure out how to make it all fit. Many of us have an irregular sleep cycle, staying up and sleeping in some days, and trying to rise before the first respectable glimmer of dawn the next day.

But a new study presented at the 2009 meeting of the Society for Neuroscience shows how disrupting your sleep cycle can interfere with your health and cognitive function. (1) Researchers from Rockefeller University disrupted the circadian rhythms of mice by exposing them to 10 hours of light followed by 10 hours of darkness. After two months of this, the mice were in need of more than a little nap. They had difficulty learning. They were more impulsive. And they got fat, thanks in part to changes in appetite hormones and metabolism.

These changes all reflect a problem with one thing: self-regulation. Even at the most basic task of homeostasis-maintaining normal body temperature-these mice were messed up. One reason why: The researchers found changes in the animals' medial prefrontal cortex, the area of the brain most important for self-control. This area of the brain is especially sensitive to disruptions in sleep and diet.

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This isn't the first study to show that interrupting natural sleep cycles is harmful. A previous study (whose mouse participants were even more unfortunate) found that chronic jet lag can be fatal. (2) Uh, yikes. Suddenly my frequent flier miles are looking less appealing. Another study, this time with hamsters in the unfortunate role of the sleep-disrupted, found that altering natural circadian rhythms results in systemic organ disease. (3)

Plenty of other studies have found that the more common sleep problem-not enough-interferes with stress management, emotion regulation, learning, and willpower.

In my Science of Willpower course at Stanford University, I make a strong case for sleep as the most powerful resource for greater self-control and better performance at whatever matters most to you. A recent article in the New York Times reported on a study from Stanford showing that sleeping 10 hours a night improved the performance of athletes. The interesting thing about this study was how great everyone felt sleeping 10 hours a day-as if they had never known what their actual potential was when they were sleep-deprived.

Getting enough sleep, on a regular cycle, may make us a better version of ourselves. And even though my greatest wish is usually more time in the day, I'd rather feel good and perform well than get to be a crankier, impulsive, sick version of myself for a few extra hours a day.

Studies Cited:
1. Society for Neuroscience presentation (October 28 2009). Disruption of circadian rhythms affects both brain and body, mouse study finds. ScienceDaily. Retrieved October 28, 2009, from http://www.sciencedaily.com¬ /releases/2009/10/091026225744.htm.
2. Davidson, A.J., et al. (2006). Chronic jet-lag increases mortality in aged mice. Current Biology, 16 (21), R914-R916.
3. Martino, T.A. (2008). Circadian rhythm disorganization produces profound cardiovascular and renal disease in hamsters. Am J Physiol Regul Integr Comp Physiol, 294(5):R1675-83.

Kelly McGonigal, Ph.D., is a health psychologist at Stanford University.

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