What Lack of Sleep Does to Your Mind

Sleepiness can damage your judgment, work performance, mood, and safety.

From the WebMD Archives

Do you often forget things that you’re sure you know? Is it hard to concentrate on complex assignments? Do you get less than six hours of sleep a night?

If so, you’re probably not getting enough sleep. That’s right; lack of sleep can hinder you from thinking clearly and keeping your emotions at an even keel. Studies show that excessive sleepiness can hurt work performance, wreak havoc on relationships, and lead to mood problems like anger and depression.

Why Don’t People Value Sleep?

Most people who don’t get enough sleep don’t recognize the toll that it takes on their cognitive and mental health.

Many people think of sleep simply as a luxury -- a little downtime. They know they feel better when they get a good night’s sleep and worse when they don’t. But sleep actually improves learning, memory, and insight.

“You’re putting energy in the bank when you go to sleep,” says Barry Krakow, MD, medical director of Maimonides Sleep Arts and Sciences, Ltd. in Albuquerque, N.M., and author of Sound Sleep, Sound Mind: 7 Keys to Sleeping Through the Night. “On a cellular level, the body is literally repairing and restoring itself. Without it, you can’t do what you want -- physically or mentally.”

And catching up on your sleep is a bigger job than many people realize. If you get less than six hours of sleep a night for a week, for example, you’ll rack up a full night’s sleep debt -- too much to make up for with a few hours extra sleep on the weekend.

The Impact of Chronic Sleepiness

People who are sleep deprived often say they feel “foggy.” Here are three reasons.

1. Sleepiness slows down your thought processes. Scientists measuring sleepiness have found that sleep deprivation leads to lower alertness and concentration. It’s more difficult to focus and pay attention, so you’re more easily confused. This hampers your ability to perform tasks that require logical reasoning or complex thought.

Sleepiness also impairs judgment. Making decisions is more difficult because you can’t assess situations as well and pick the right behavior.

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2. Excessive sleepiness impairs memory. Research suggests that the nerve connections that make our memories are strengthened during sleep. “Sleep embeds the things that we have learned and experienced over the course of the day into our short-term memory,” says Avelino Verceles, MD, assistant professor at the University of Maryland School of Medicine and director of the school’s sleep medicine fellowship.

It appears that different phases of sleep play different roles in consolidating new information into memories. If your sleep is cut short or disrupted, it interferes with these cycles.

When you’re sleepy, you may forget and misplace things often. And the inability to focus and concentrate caused by sleepiness further weakens memory. “If you’re not able to concentrate on what’s at hand, it’s not going to make it into your short-term memory and then long-term memory,” says Allison T. Siebern, PhD, a Fellow in the Insomnia and Behavioral Sleep Medicine Program at the Stanford University Sleep Medicine Center.

3. Poor sleep makes learning difficult. Sleep deprivation affects your ability to learn in two ways. Because you can’t focus as well, it’s more difficult to pick up information, so you can’t learn efficiently. It also affects memory, which is essential to learning. In children, sleepiness can lead to hyperactivity, also hampering learning. Teens may lose the focus, diligence, and memory capacity to perform well in school.

The Biggest Danger of Sleepiness: Slowed Reaction Time

Sleepiness makes your reaction time slower, a special problem when driving or doing work or other tasks that require a quick response. The National Highway Traffic Safety Administration conservatively estimates that at least 100,000 crashes reported to police each year are due to driver fatigue. Other estimates put that number at 1 million -- 20% of all crashes. Nearly one-third of Americans in the National Sleep Foundation’s 2009 poll reported nodding off while driving.

You don’t need to fall asleep at the wheel to be a danger -- drowsiness alone can be as dangerous as driving drunk. Driving while sleepy is like driving with a blood alcohol content of .08% -- over the legal limit in many states. And drinking and drowsiness are double trouble when driving because sleep deprivation magnifies the affects of alcohol.

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The people at highest risk for fatigue-related auto accidents are teenagers and young adults, especially men. Shift workers who work at night or work long or irregular hours and people with untreated sleep disorders such as sleep apnea and narcolepsy are also at high risk.

A slowed reaction time can endanger lives in other ways. In a 2009 study done with cadets at the United States Military Academy at West Point, researchers from the University of Texas in Austin found that sleep deprivation hampered information-integration. This is a function of the mind that relies heavily on split-second, gut-feeling decisions. The researchers noted that this could be a particular concern for firefighters, police officers, soldiers, and others who are often sleep deprived on the job.

The Impact of Sleepiness on Mood and Mental Health

Lack of sleep can alter your mood significantly. It causes irritability and anger and may lessen your ability to cope with stress. According to the NSF, the “walking tired” are more likely to sit and seethe in traffic jams and quarrel with other people. Sleep-deprived people polled by the NSF were also less likely than those who sleep well to exercise, eat healthfully, have sex, and engage in leisure activities because of sleepiness.

“Over time, impaired memory, mood, and other functions become a chronic way of life,” says Siebern. “In the long term, this can affect your job or relationships.”

Chronic sleepiness puts you at greater risk for depression. They are so closely linked that sleep specialists aren’t always sure which came first in their patients. “Sleep and mood affect each other,” says Verceles. “It’s not uncommon for people who don’t get enough sleep to be depressed or for people who are depressed to not sleep well enough.”

How Do You Know if Sleepiness Is a Problem?

Because individual sleep needs vary, experts say the best way to gauge whether you’re getting enough sleep is by how you feel. “You shouldn’t feel sleepy when you wake up,” says Verceles. “You should be energetic throughout the day and slowly wind down as you approach your usual bedtime.”

Krakow suggests assessing your day-to-day abilities and quality of life. “Ask yourself if your cognitive performance is where you want it to be,” he says. “Are you having conflicts with other employees or your boss over your memory, attention, or concentration -- and particularly your productivity?”

WebMD Feature Reviewed by Hansa D. Bhargava, MD on April 30, 2013

Sources

SOURCES:

Maddox, W.T. Sleep, 2009; vol 32: pp 1439-1448.

Taylor, D.J. Sleep, Nov. 1, 2005; vol 28: pp 1457-1464.

National Sleep Foundation: “2009 Sleep in America Poll Highlights and Key Findings,” “2002 Adult Sleep Habits,” “Teens and Sleep.”

National Institute of Neurological Disorders and Stroke: “Brain Basics: Understanding Sleep.”

WebMD Feature: “The Toll of Sleep Loss in America.”

NIH National Heart, Lung and Blood Institute: “Your Guide to Healthy Sleep.”

Barry Krakow, MD, medical director, Maimonides Sleep Arts and Sciences, Ltd., Albuquerque, N.M.; author, Sound Sleep, Sound Mind: 7 Keys to Sleeping Through the Night.

Harvard Medical School: “Sleep, Performance, and Public Safety,” “Sleep, Learning, and Memory.”

Avelino Verceles, MD, assistant professor and director, sleep medicine fellowship, University of Maryland School of Medicine, Baltimore.

Allison T. Siebern, PhD, fellow, Insomnia and Behavioral Sleep Medicine Program, Stanford University School of Medicine, Sleep Medicine Center, Redwood City, Calif.

U.S. Department of Health and Human Services: “Your Guide to Healthy Sleep.”

WebMD Medical Reference: “Sleep 101.”

National Highway Traffic Safety Administration: “Drowsy Driving and Automobile Crashes.”

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