We spend a quarter of our lives asleep. Sleep is necessary for the body to rest, yet our brains continue to process information. Studies have shown that students are more successful when they sleep after studying-instead of pulling all-nighters-because the brain reviews information learned. Similarly, dreaming is an opportunity to work out emotional problems and form thoughts and memories. About 25 percent of the time spent sleeping is spent in rapid eye movement, or REM, sleep. This type of sleep is known for when dreams occur, but it also helps energize the brain and body. Researchers have found two important factors regarding humans and sleep: basicsleep need and sleep debt. Basic sleep need is the amount of sleep we need to have regularly to perform at our best. Sleep debt is the loss of sleep. A few studies say that most adults function best with a basic sleep need of seven to eight hours a night. The problem is that sleep debt also factors in, just because that you meet your basic sleep needs a few nights of the week doesn't mean it cancels out the effects of one night's sleep debt. Of course, everyone is different and some people require more or less sleep than the standard basic sleep need. But the real problem lies in what lack of sleep does over the long period to people who either does not meet his or her body's needs or for one reason or another doesn't get enough regular sleep. It is more possible for these people to have motor vehicle accidents, weight gain and risk for heart disease or diabetes   and may be at increased risk for psychological conditions such as depression or drug abuse. Sleeping too long also can be associated with depression and poor health. The best title for the passage is   _  .
Why We Need Sleep REMSleep and Basic Sleep Sleep Causes Problems How Much Sleep We Need