There's nothing like a good night's sleep -- but what does that really mean? It turns out that the answer depends not only on your age, but also on your lifestyle. Some people are productive and happy with fewer hours of sleep, while others need more. Still, experts can determine guidelines that work for most people. The National Sleep Foundation researched the topic and gave new recommendations this week. The foundation acknowledges that sleep needs will vary -- lifestyle and stress should be taken into consideration -- but their recommendations offer a general guideline. For example, teenagers (14 --17 years old) need 8--10 hours' sleep every day. To create the recommendations, some sleep and medical experts reviewed 312 articles from journals published during the last decade. This is the first time that any professional organization has developed age-specific recommended sleep durations based on a systematic review of the world scientific literature. A lack of sleep can be linked to weight gain, because that causes an increase in appetite, according to the foundation. It can also have serious consequences on the brain. People who do not get enough sleep are at increased risk for depression, and can endanger others. Those that become sleepy while driving, for example, risk both their lives and the lives of those around them. Researchers also have found in the past that too much sleep can have negative effects. Low socioeconomic status and depression reportedly are significantly associated with longer sleep. However, experts nowadays find that research on oversleeping is still unconvincing and needs more attention. Currently, there is no strong evidence that sleeping too much has health consequences. There is, however, laboratory evidence that short sleep durations of four to five hours have negative consequences. We need similar laboratory studies to determine whether long sleep durations result in physiological changes that could lead to disease before we make any recommendations against sleep extension. The research shows that people without enough sleep will   _  .
lose some weight drive faster than usual dream during their sleep eat more food