Garrett had a hard time waking up for school during his sophomore year. At first he thought it was because he'd been going to bed late over summer vacation and then sleeping in the next day. He assumed he'd adjust to his school schedule after a couple of weeks. But as the school year progressed, Garrett found himself lying awake in bed until 2 or 3 in the morning, even though he got up at 6:30 AM every day. He began falling asleep in class and his grades started to suffer.

Most teens don't get enough sleep, but that's usually because they're overloaded and tend to skimp on sleep. But sleep problems can keep some teens, like Garrett, awake at night even when they want to sleep.

Over time, those nights of missed sleep (whether they're caused by a sleep disorder or simply not scheduling enough time for the necessary ZZZs) can build into a sleep deficit. People with a sleep deficit are unable to concentrate, study, and work effectively. They can also experience emotional problems, like depression.

What Happens During Sleep?
You don't notice it, of course, but while you're asleep, your brain is still active. As people sleep, their brains pass through five stages of sleep. Together, these stages - which doctors call 1, 2, 3, 4, and REM (rapid eye movement) sleep - make up a sleep cycle. One complete sleep cycle lasts about 90 to 100 minutes. So during an average night's sleep, a person will experience about four or five cycles of sleep.

Stages 1 and 2 are periods of light sleep from which a person can easily be awakened. During these stages, eye movements slow down and eventually stop, heart and breathing rates slow down, and body temperature decreases. Stages 3 and 4 are deep sleep stages. It's more difficult to awaken someone during these stages, and when awakened, a person will often feel groggy and disoriented for a few minutes. Stages 3 and 4 are the most refreshing of the sleep stages - it is this type of sleep that we crave when we are very tired.

The final stage of the sleep cycle is known as REM sleep because of the rapid eye movements that occur during this stage. During REM sleep, other physical changes take place - breathing becomes rapid, the heart beats faster, and the limb muscles don't move. This is the stage of sleep when a person has the most vivid dreams.

Why Do Teens Have Trouble Sleeping?
Research shows that teens need 8 1/2 to more than 9 hours of sleep a night. You don't need to be a math whiz to figure out that if you wake up for school at 6:00 AM, it means you have to go to bed at 9:00 PM to reach the 9-hour mark. Studies have found that many teens, like Garrett, have trouble falling asleep that early, though. It's not because they don't want to sleep. It's because their brains naturally work on later schedules and aren't ready for bed.

During adolescence, the body's circadian (pronounced: sur-kay-dee-un) rhythm (sort of like an internal biological clock) is reset, telling a teen to fall asleep later at night and wake up later in the morning. This change in the circadian rhythm seems to be due to the fact that melatonin, a hormone that regulates sleeping and waking patterns, is produced later at night in teens than it is for kids and adults, making it harder for teens to fall asleep. This phenomenon has a medical name: delayed sleep phase syndrome. Although it's common, delayed sleep phase syndrome doesn't affect every teen.

For some people, insomnia can be made worse by worrying about the insomnia itself. A brief period of insomnia can build into something longer lasting when a person becomes anxious about not sleeping or worried about feeling tired the next day. Doctors call this psychophysiologic (pronounced: sye-ko-fih-zee-uh-lah-jik) insomnia.

There are a number of other conditions that can disrupt sleep in teens. They include:

Periodic Limb Movement Disorder and Restless Legs Syndrome
People with these conditions find their sleep is disrupted by leg (or, less frequently, arm) movements, leaving them tired or irritable from lack of sleep. In the case of periodic limb movement disorder (PLMD), these movements are involuntary twitches or jerks: They're called involuntary because the person isn't consciously controlling them and is often unaware of the movement. People with restless legs syndrome (RLS) actually feel physical sensations in their limbs, such as tingling, itching, cramping, or burning. The only way they can relieve these feelings is by moving their legs or arms to get rid of the discomfort.

Doctors can treat PLMD and RLS. For some people, treating an iron deficiency makes RLS go away; other people may need to take other types of medication.

Obstructive Sleep Apnea
This sleep disorder causes a person to stop breathing temporarily during sleep. One common cause of obstructive sleep apnea is enlarged tonsils or adenoids (tissues located in the passage that connects the nose and throat). Being overweight or obese can also lead a person to develop obstructive sleep apnea.

People with obstructive sleep apnea may snore, have difficulty breathing, and even sweat heavily during sleep. Because sleep apnea disrupts a person's sleep, people with the disorder may feel extremely sleepy or irritable during the day. People who show signs of obstructive sleep apnea, such as loud snoring or excessive daytime sleepiness, should be evaluated by a doctor.

Reflux
Some people have a condition called gastroesophageal reflux disease (GERD) that causes stomach acid to move backward up into the esophagus. This produces the uncomfortable, burning sensation we call heartburn. The symptoms of GERD can be worse when a person is lying down. So even if the person doesn't notice the feelings of heartburn because he or she is sleeping, the discomfort it causes can still interfere with the sleep cycle.

Nightmares
Most teens have nightmares on occasion, but frequent nightmares can disrupt a person's sleep patterns by waking him or her during the night. Some things can trigger more frequent nightmares, including certain medications, drugs, or alcohol. And, ironically, sleep deprivation can also be a cause. The most common triggers for more frequent nightmares, though, are emotional, such as stress or anxiety. If nightmares are interfering with your sleep, it's a good idea to talk to a doctor, therapist, or other counselor.

Sleepwalking
It's rare for teens to walk in their sleep; most sleepwalkers are children. Sleepwalking may run in families. It most often occurs when a person is sick, has a fever, is not getting enough sleep, or is feeling stress.

Because most sleepwalkers don't sleepwalk often, it's not usually a serious problem. Sleepwalkers tend to go back to bed on their own and don't usually remember sleepwalking. (Sleepwalking often happens during the deeper sleep that takes place during stages 3 and 4 of the sleep cycle.) Sometimes, though, a sleepwalker will need help moving around obstacles and getting back to bed. It's also true that waking sleepwalkers can startle them (but it isn't harmful), so try to guide a sleepwalker back to bed gently.

What Should I Do?
If you're getting enough rest at night and you're still feeling tired during the day, it's a good idea to visit your doctor. Excessive tiredness can be caused by all sorts of health problems, not just difficulties with sleep.

If your doctor suspects a sleep problem, he or she will look at your overall health and sleep habits. In addition to doing a physical examination, the doctor will ask you about any concerns and symptoms you have, your past health, your family's health, any medications you're taking, any allergies you may have, and other issues. This is called the medical history. Your doctor may also do tests to find out whether any conditions - such as obstructive sleep apnea - might be interfering with your sleep.

Different sleep problems are treated differently. Some can be treated with medications, whereas others can be helped by special techniques such as light therapy (where a person sits in front of a light box for a certain amount of time each day) or other practices that can help reset a person's body clock.

Doctors also encourage teens to make lifestyle changes that promote good sleeping habits. You probably know that caffeine can make you stay awake, but did you know that playing video games or watching TV before sleeping can do the same thing? Check out the More Articles Like This tab for additional suggestions on improving the quality of your sleep.