A 12-year-old girl asked her mother to take her to a psychiatrist because she thought she was going crazy. Several times over the previous month, she had awakened in the morning to find herself dressed in an odd assortment of clothes which had been hanging in her closet the night before.

One night, her mother heard the bathtub water running at 2 a.m., and found her daughter in the tub dressed in her ballet leotard. She spoke to her daughter, but the girl did not answer. Instead, she simply got out of the tub and returned to her bed. The next morning she had no memory of anything happening during the night. She was experiencing a sleepwalking disorder.

Every day in my psychiatry practice I see patients who report they are having trouble sleeping. Usually they are frustrated because they can’t fall asleep, stay asleep or wake up refreshed in the morning. Sometimes they are bothered by nightmares or sleepwalking.

Parents may report that their child refuses to cooperate at bedtime or that they don’t settle down until 11 or 12 at night, when they eventually fall asleep in front of the TV. Adults may toss and turn for hours and sleep restlessly.

Sleep disorders may occur at any stage of life. One-third of all U.S. adults experience some type of sleep disorder. Some sleep problems are secondary to medical or psychiatric conditions.

Occasionally poor sleep stems from social or physical habits that may have been established earlier in life, or in response to recent stress. Environmental factors such as physical comfort, light, noise and relationships with others in the home also may aid or hinder sleep. In addition, sleep patterns vary throughout life from before birth to old age.

Factors that place individuals at higher risk for sleep disorders include female gender, the presence of mental and medical disorders, substance abuse and advanced age.

Individuals’ requirements for sleep vary. Some people may feel refreshed with little sleep, while others may need several hours more sleep each night in order to feel refreshed. Short duration of sleep does not necessarily signal a sleep disorder.

Four major symptoms characterize most sleep disorders: insomnia, hypersomnia, parasomnia and sleep-wake schedule disturbance. These symptoms frequently overlap.

Insomnia is difficulty in initiating or maintaining sleep. It is the most common sleep complaint and may be transient or persistent. Difficulty falling asleep may be secondary to painful or uncomfortable physical conditions, anxiety, environmental changes or depression.

Trouble staying asleep may be caused by medical conditions such as sleep apnea, dietary factors, aging and substance use or withdrawal – including alcohol. It also may be caused by mental conditions such as depression, post-traumatic stress disorder and schizophrenia.

Brief periods of insomnia are often associated with anxiety. If the insomnia continues over an extended period of time, the person may develop additional stress secondary to their frustration about not being able to sleep. The anxiety about sleeplessness then makes initiation of sleep even more difficult.

Hypersomnia refers to excessive amounts of sleep, excessive daytime sleepiness, the tendency to fall asleep suddenly while awake and active, or difficulty staying awake. Medical conditions such as narcolepsy, sleep apnea and use or withdrawal of medications, drugs or alcohol can cause this. Mental conditions such as depression or avoidance reactions to escape life stressors can also trigger hypersomnia.

Parasomnia is an unusual or undesirable event that appears suddenly during sleep or in the period of time between waking and sleeping, including nightmares, night terrors and sleepwalking. These are most often seen in children.

Nightmares occur during the rapid eye movement, or REM, phase of sleep, and usually late at night. Some people have frequent nightmares as a lifelong condition; others have them at times of illness or stress. No harm comes from awakening a person who is having a nightmare. When nightmares are an ongoing significant problem, medicines can suppress REM sleep and reduce the frequency of nightmares.

Night terrors are distinguished from nightmares in that they are associated with simply awakening in terror. The person generally has no dream to recall beyond a single frightening image. Typically, the person sits up in bed with a frightened expression, screams loudly and may awaken with a sense of terror. It may develop into a sleepwalking episode after the original scream.

The fourth major symptom of sleep disturbance is disturbance of the sleep-wake schedule. The person can’t sleep when he wants to, but is able to sleep at other times. Also, he doesn’t feel fully awake when he wants to be. This may result in the person sleeping through the day then staying awake at night.

In future columns we will look more closely at specific sleep patterns and disorders found in infancy, childhood and adolescence, and adulthood. Also, we will address some of the more common medical and mental health issues that can affect sleep.

Dr. Corabell Arps is a child and adolescent psychiatrist and assistant medical director at The Acadia Hospital.