More than 80 sleep disorders have been identified. These are divided into four major categories:
Problems with falling asleep and staying asleep
Also known as insomnia, these problems are brought on by disturbances in the regular wake/sleep pattern. Causes may include psychological factors such as anxiety and depression, respiratory difficulties, limb movements during sleep or physiologic disorders such as hyperthyroidism.
Problems staying awake
Often referred to as sleepiness, these problems include sleep apnea and narcolepsy (uncontrollable sleepiness). Normal lifestyle is disrupted because sleep is fragmented, and since the person may fall asleep at any time, accidents and other life-threatening results may occur.
Sleep disruptive behaviors
These disorders, known as parasomnias, are associated with sleep and the different phases of sleep itself, such as nocturnal seizures, sleepwalking, night terrors and bed- wetting.
Problems maintaining a regular sleep schedule
Lifestyles that require an irregular sleep/wake pattern, such as alternating shift work or frequent cross-country flights (jet lag) fall into this category. People affected by these disorders have chronic difficulty in falling asleep at conventional times.