This is the second article in a two-part series on childhood sleep disorders. The first article on pre-adolescent sleep disorders appeared last week in Sunday's Lifestyle section. This article is dedicated to common sleep disorders in adolescence and in the teenage years.

Many of the sleep disorders mentioned in last week's article, such as sleep walking, night terrors and nightmares, can persist into adolescence, but fortunately they tend to decrease in frequency with age.

Sleep apnea, however, tends to become more prevalent in adolescents and teens than it is in very young children. Two factors are likely responsible for this increase in prevalence: the peak in the size of tonsils in adolescence and the increasing prevalence of childhood obesity. There is no question that sleep apnea has a strong genetic component, but weight typically plays a role as well. As mentioned in the previous article, tonsillectomy is often performed for childhood sleep apnea, and it is usually effective.

The benefits of treatment are well established, including improvement in behavior and school performance, not to mention improved cardiovascular health. Screening for childhood sleep apnea is as simple as listening for snoring or irregularities in the breathing pattern. If there is associated daytime sleepiness or hyperactive behaviors, a sleep evaluation might be indicated.

The most common sleep disorder in adolescents and teens is inadequate sleep time. (Incidentally, this is the most common sleep disorder in adults as well). Teens still require 9 or more hours of sleep a night, but most are not close to that amount on a regular basis. Homework burden, after-school activities, television and early school start times are typically the culprits.

Ensuring an adequate opportunity to sleep is essential for normal growth and development. It is also essential to prevent one of the biggest public health consequences of sleep disorders in teens: drowsy driving. Surveys have consistently shown that teens on average are sleeping 7 to 7.5 hours a night, far less than the 9 to 9.5 hours that is needed.

This sleep deprivation can impair judgment and slow down reaction time, both of which are essential to safely operate a motor vehicle. A more extreme case of staying up all night is as impairing to the driver as being legally drunk.

One of the more common sleep disorders in teens is delayed sleep phase syndrome. Under the changing hormone levels in the teenage years, there is a natural tendency to shift to a later bed and wake time. For example, if the normal sleep wake rhythm (or circadian rhythm) is shifted to a bedtime of midnight and a rise time of 9 a.m., it is going to be a challenge to have that teenager in school and functional by 8 a.m.

One solution would be to delay school start times, especially for high school. In the absence of such policy change, teaching the brain a new sleep wake rhythm through light therapy can be effective. In consultation with your physician, the appropriate timing and intensity of light delivered through commercially available light boxes can effectively shift the bed and wake times earlier. Usually, although, the delayed sleep phase syndrome does not persist into adulthood.

Restless legs syndrome tends to appear in the teenage years. This disorder consists of a feeling of the need to move the limbs (usually the legs) that is only alleviated by movement of the limbs, such as getting up and walking around. These symptoms are usually worsened by rest and inactivity and are more severe in the evening than in the daytime. These symptoms are often associated with a disorder called periodic limb movements of sleep. These involuntary leg movements can be associated with frequent nighttime awakenings.

The ultimate manifestation of these disorders can be either excessive daytime sleepiness or hyperactivity. In fact, studies have shown that a substantial proportion of children diagnosed with attention deficit disorder actually have a sleep disorder such as restless legs syndrome or sleep apnea.

Treatment of restless legs syndrome in teens consists of largely nonmedication approaches. These include proper sleep habits, such as a regular bed and wake time and, most importantly, adequate sleep time. A hot bath an hour or so before bed can alleviate some symptoms. Avoiding caffeine and chocolate and over-the-counter sleep aid medicines that contain diphenhydramine is essential as well because these substances can trigger restless legs symptoms.

There is an association with iron deficiency in up to 30 percent of individuals, so treatment with iron, after a cause for iron deficiency has been determined, can be helpful for those who are deficient. There are also some medications that can be used in severe cases to control the symptoms. Although very effective, they have not been well studied for use in children. Restless legs syndrome, unfortunately, tends to worsen with age.

Narcolepsy is another condition that typically appears in the teenage years. Narcolepsy is a genetic condition whose hallmark symptom is excessive daytime sleepiness. The sleepiness can be so severe that it often interferes with school and social activities.

Narcolepsy is present in one out of every 2,000 people and many children remain undiagnosed for many years. There are three other symptoms that are characteristic of narcolepsy.

Hypnogogic hallucinations, or feeling as though one is dreaming but awake, typically occur immediately upon arising in the morning.

Another phenomenon called sleep paralysis that consists of feeling paralyzed upon awakening in the morning is also common. Both of these symptoms typically last less than a minute or two and they can occasionally occur in people without narcolepsy as well.

The third characteristic symptom is quite specific for narcolepsy. It is called cataplexy and is characterized by a sudden loss of control of muscle strength after an emotional stimulus, such as anger or hearing a funny joke. All of the above mentioned symptoms, including sleepiness, can be controlled with medications and proper sleep habits.

Insomnia, although not present in teenagers as often as seen in adults, is becoming more common among teens. Stress of school and life as well as the above-mentioned sleep disorders contribute to its prevalence. Treatment and evaluation depends on the type of insomnia (initiation or maintenance of sleep), but typically consists of nonmedication modalities called cognitive behavioral therapy.

This therapy consists of multiple sessions, typically with a psychologist, to help teach the child to be a better sleeper. Our current understanding of chronic insomnia is that it persists in an individual largely due to poor sleep habits.

These poor sleep habits tend to occur as a result of insomnia sufferers self-treating their sleep difficulty. Cognitive behavioral therapy, at least in adults, has been shown to be as effective as or more effective than medication treatments for insomnia. In more severe cases that do not respond to cognitive behavioral therapy, medications can be used, but are they not well studied in children.

There are of course many more described sleep disorders in adolescents and teenagers, but those mentioned above are the most common. If your child is experiencing a chronic sleep problem and especially if it is interfering with daytime function, you should discuss this with your primary care provider to see if referral to a sleep specialist or sleep testing would be beneficial.

Mark D. Reploeg, M.D., is the head of sleep medicine at The Corvallis Clinic and is the medical director of the nationally accredited Samaritan Sleep Disorders Center. Dr. Reploeg and his colleagues treat both children and adults with all forms of sleep disorders.