Approach to the patient with a sleep or wakefulness disorder

[Michiko]

Almost half of all people in the US report sleep-related problems. Disordered sleep can cause emotional disturbance, memory difficulty, poor motor skills, decreased work efficiency, and increased risk of traffic accidents. It can even contribute to cardiovascular disorders and mortality.
(See also Sleep Apnea and Sleep Problems in Children.)
The most commonly reported sleep-related symptoms are insomnia and excessive daytime sleepiness (EDS).

Insomnia is difficulty falling or staying asleep, early awakening, or a sensation of unrefreshing sleep.
EDS is the tendency to fall asleep during normal waking hours.

EDS is not a disorder but a symptom of various sleep-related disorders. Insomnia can be a disorder, even if it exists in the context of other disorders, or can be a symptom of other disorders.
Parasomnias are abnormal sleep-related events (eg, night terrors, sleepwalking).