ost teens need about 8½ to more than 9 hours of sleep each night. The right amount of sleep is essential for anyone who wants to do well on a test or play sports without tripping over their feet. Unfortunately, though, many teens don't get enough sleep.
Why Aren't Teens Getting Enough Sleep?
Until recently, teens were often given a bad rap for staying up late, oversleeping for school, and falling asleep in class. But recent studies show that adolescent sleep patterns actually differ from those of adults or kids.

These studies show that during the teen years, the body's circadiancircadian rhythm (sort of like an internal biological clock) is temporarily reset, telling a person to fall asleep later and wake up later. This change in the circadian rhythm seems to be due to the fact that the brain hormone melatoninmelatonin is produced later at night for teens than it is for kids and adults. This can make it harder for teens to fall asleep early.

These changes in the body's circadian rhythm coincide with a time when we're busier than ever. For most teens, the pressure to do well in school is more intense than when they were kids, and it's harder to get by without studying hard. And teens also have other time demands — everything from sports and other extracurricular activities to fitting in a part-time job to save money for college.

Early start times in some schools may also play a role in this sleep deficit. Teens who fall asleep after midnight may still have to get up early for school, meaning that they may only squeeze in 6 or 7 hours of sleep a night. A couple hours of missed sleep a night may not seem like a big deal, but can create a noticeable sleep deficit over time.

Why Is Sleep Important?
This sleep deficit impacts everything from a person's ability to pay attention in class to his or her mood. Research shows that more than 20% of high school students fall asleep in class, and experts have been able to tie lost sleep to poorer grades. Lack of sleep also damages teens' ability to do their best in athletics.

Slowed responses and concentration from lack of sleep don't just affect school or sports performance, though. The fact that sleep deprivation slows reaction times can be life threatening for people who drive. The National Highway Safety Traffic Administration estimates that 1,500 people are killed every year in crashes caused by drivers between the ages of 15 and 24 who are simply tired. (More than half of the people who cause crashes because they fall asleep at the wheel are under the age of 26.)

Lack of sleep has also been linked to emotional troubles, such as feelings of sadness and depression. Sleep helps keep us physically healthy, too, by slowing our body's systems enough to re-energize us after everyday activities.

How Do I Know if I'm Getting Enough?
Even if you think you're getting enough sleep, you may not be. Here are some of the signs that you may need more sleep:

difficulty waking up in the morning
inability to concentrate
falling asleep during classes
feelings of moodiness and even depression
How Can I Get More Sleep?

Recently, some researchers, parents, and teachers have suggested that middle- and high-school classes begin later in the morning to accommodate teens' need for more sleep. Some schools have already implemented later start times. You and your friends, parents, and teachers can lobby for later start times at your school, but in the meantime you'll have to make your own adjustments.

Here are some things that may help you to sleep better:

Set a regular bedtime. Going to bed at the same time each night signals to your body that it's time to sleep. Waking up at the same time every day can also help establish sleep patterns. So try to stick to your sleep schedule even on weekends. Don't go to sleep more than an hour later or wake up more than 2 to 3 hours later than you do during the week.

Exercise regularly. Try not to exercise right before bed, though, as it can rev you up and make it harder to fall asleep. Many sleep experts believe that exercising 5 or 6 hours before bedtime (in late afternoon) may actually help a person sleep.

Avoid stimulants. Don't drink beverages with caffeine, such as soda and coffee, after 4 PM. Nicotine is also a stimulant, so quitting smoking may help you sleep better. And drinking alcohol in the evening can also cause a person to be restless and wake up during the night.

Relax your mind. Avoid violent, scary, or action movies or television shows right before bed — anything that might set your mind and heart racing. Reading books with involved or active plots may also keep you from falling or staying asleep.

Unwind by keeping the lights low. Light signals the brain that it's time to wake up. Staying away from bright lights (including computer screens!), as well as meditating or listening to soothing music, can help your body relax.

Don't nap too much. Naps of more than 30 minutes during the day may keep you from falling asleep later.

Avoid all-nighters. Don't wait until the night before a big test to study. Cutting back on sleep the night before a test may mean you perform worse than you would if you'd studied less but got more sleep.

Create the right sleeping environment. Studies show that people sleep best in a dark room that is slightly on the cool side. Close your blinds or curtains (and make sure they're heavy enough to block out light) and turn down the thermostat in your room (pile on extra blankets or wear PJs if you're cold). Lots of noise can be a sleep turnoff, too.

Wake up with bright light. Bright light in the morning signals to your body that it's time to get going.

If you're drowsy, it's hard to look and feel your best. Schedule "sleep" as an item on your agenda to help you stay creative and healthy.

对于大多数青少年来说，8.5-9个小时的睡眠是必需的。适量的睡眠是保证大家考试能正常发挥，运动能不绊到脚的关键。但可惜的是，许多青少年都没有足够的睡眠。

为什么青少年不能得到充足的睡眠？

一直以来，人们都会指责青少年晚上睡的太晚，上学睡过头以及上课时间睡觉。但是最近的研究表明，青少年的睡眠模式与成年人或小孩有本质区别。

这些研究指出，在青春期期间，青少年身体的24小时生理节奏（有点类似体内的生物钟）被临时重置， 从而导致青少年睡的更晚，醒的更迟。24小时生理节奏的改变可能是由于青少年在夜间产生的大脑荷尔蒙褪黑激素比大人和小孩都更晚。而这也同样能使青少年更晚入睡。

这些体内24小时生理节奏的改变与我们在较忙碌时期的改变一致。大多数的青少年都承受着比自己幼年时期更大更紧张的学习压力，且他们只有通过更努力学习才能克服这些压力。同时，青少年还有其他时间上的要求---运动，一些课外活动，以及为了上大学攒钱而做兼职，等等。

某些学校较早的上课时间可能也是导致睡眠不足的原因之一。假如青少年在午夜之后才睡但又得起早去上学，这就意味着他们一天只能挤出6-7个小时睡觉。一个晚上少几个小时的睡眠不会产生什么大问题，但是长期少眠就会造成严重的睡眠不足。

为什么睡眠如此重要？

睡眠不足会影响一切。如很难在上课时候集中注意力或影响一个人的心情。研究表明，超过20%的高中生会在上课的时候睡觉。专家也已证明缺眠会使成绩下降。缺乏睡眠也会影响青少年在运动中展现自己的最佳状态。

但是由于缺乏睡眠而引起的反应迟钝和注意力下降并不仅仅影响到学习和运动。睡眠不足还会影响驾车人的生活。全国高速安全交通管理局估计，每年大约有1500位年龄在15—24岁之间的年轻人因为疲劳而死于车祸（驾车时睡着而发生车祸的人中有半数以上年龄在26岁以下。

伤心失落情绪低下等问题也与睡眠不足息息相关。睡眠还能通过充分放慢身体系统使还原每天消耗的体力来帮助我们保持身体健康。

如何知道自己是否已有充足睡眠？

即使你觉得自己已经睡饱了，你可能还是没有得到充分的睡眠。如果出现以下几种情况表明你还需要更多睡眠：

早晨很难醒来。
注意力难以集中。
上课时睡着。
心情抑郁甚至沮丧。
如何得到更多睡眠？

近来，一些研究人员，家长和老师都老师都建议中学和高中推迟早上上课时间来适应青少年更多睡眠的需要。有些学校已经开始实行。你和你的朋友，家长以及老师在学校里倡议上课时间推迟，但与此同时，你必须保证自己能适应。

以下几件事能帮助你更好的获得睡眠：

设定规律的就寝时间。每天晚上都在同一个时间睡觉会向你的身体发出信号“睡觉时间到了”。每天早晨在同一时间点醒来也能帮助建立睡觉模式。因此，即使在周末也要坚持这个睡觉时间表，不要晚上晚睡一小时或早晨晚起2－3个小时。

定期运动。但是不要在睡觉前运动，因为它会使你兴奋更难入睡。许多睡眠专家认为，睡前5 －6小时（下午）的运动确实能助眠。

远离刺激品。下午4点之后不要喝含有咖啡因的饮料，如苏打水或咖啡。尼古丁也属于刺激品，因此戒烟能让你睡得更好。晚上喝酒也会使人休息不充分以及在夜间醒来。

放松大脑。睡前不要观看暴力，恐怖或动作电影或电视－－这些都会使你的大脑和心跳加速。看带有复杂或动作情节的书也会让你睡不着或睡不好觉。
将灯低放，放松身体。灯光会向大脑发出醒来信号。远离亮光（包括电脑屏幕），以及调轻或倾听舒心柔和的音乐能帮助我们身体放松下来。

不要小睡过多。白天打盹超过30分钟会使你在晚上睡得更晚。

不要通宵：不要在晚上才为重大考试作准备。因为第二天的考试而削减睡觉时间只会比你复习少但睡眠充足更糟糕。

营造正确的睡觉环境。研究表明，人们在黑暗房间那靠较凉的一边睡得最好。关上窗户拉上窗帘（确保窗帘能挡住亮光）。关掉房间内的暖气（如果太冷，你可以加盖一条毯子或传上睡衣）。各种噪音都可能会中断睡眠。

在光亮中醒来。清晨的亮光提醒你的身体清醒。

如果你很昏昏欲睡，你就很难让人看出和感觉到你最好的东西。将睡眠作为你日程的一部分，你将更活泼健康