What Does Sleep Do for You?

A number of tasks vital to health and quality of life are linked to sleep, and these tasks are impaired when you are sleep deprived.

Learning, Memory, and Mood

Students who have trouble grasping new information or learning new skills are often advised to "sleep on it," and that advice seems well founded. Recent studies reveal that people can learn a task better if they are well rested. They also can remember better what they learned if they get a good night's sleep after learning the task than if they are sleep deprived. Volunteers had to sleep at least 6 hours to show improvement in learning, and the amount of improvement was directly tied to how much time they slept. In other words, volunteers who slept 8 hours outperformed those who slept only 6 or 7 hours. Other studies suggest that all the benefits of training for mentally challenging tasks are maximized after a good night's sleep, rather than immediately following the training or after sleeping for a short period overnight. Many well-known artists and scientists claim to have had creative insights while they slept.

Mary Shelley, for example, said the idea for her novel Frankenstein came to her in a dream. Although it has not been shown that dreaming is the driving force behind innovation, one study suggests that sleep is needed for creative problem solving. In that study, volunteers were asked to perform a memory task and then were tested 8 hours later. Those who were allowed to sleep for 8 hours immediately after receiving the task and before being tested were much more likely to find a creative way of simplifying the task and improving their performance compared to those who were awake the entire 8 hours before being tested.

Exactly what happens during sleep to improve our learning, memory, and insight isn't known. Experts suspect, however, that while people sleep, they form or reinforce the pathways of brain cells needed to perform these tasks. This process may explain why sleep is needed for proper brain development in infants.

Not only is a good night's sleep required to form new learning and memory pathways in the brain, but sleep is also necessary for those pathways to work up to speed. Several studies show that lack of sleep causes thinking processes to slow down. Lack of sleep also makes it harder to focus and pay attention. Lack of sleep can make you more easily confused. Studies also find a lack of sleep leads to faulty decisionmaking and more risk taking. A lack of sleep slows down your reaction time, which is particularly significant to driving and other tasks that require quick response. When people who lack sleep are tested by using a driving simulator, they perform just as poorly as people who are drunk. (See "Crash in Bed Not on the Road".) The bottom line is: not getting a good night's sleep can be dangerous!

Even if you don't have a mentally or physically challenging day ahead of you, you should still get enough sleep to put yourself in a good mood. Most people report being irritable, if not downright unhappy, when they lack sleep. People who chronically suffer from a lack of sleep, either because they do not spend enough time in bed or because they have an untreated sleep disorder, are at greater risk of developing depression. One group of people who usually don't get enough sleep is mothers of newborns. Some experts think depression after childbirth (postpartum blues) is caused, in part, by a lack of sleep.