Home > Encyclopedia of Mental Disorders > Insomnia

Definition

Insomnia is a condition that occurs when a person in unable to get long enough or refreshing enough sleep at night. Insomnia can result from an inability to fall asleep, an inability to stay asleep, or waking too early before having gotten enough sleep.

Description

Insomnia is a disorder in which people are unable to get enough, or enough restorative, sleep because of one or more factors. People with insomnia often have daytime symptoms related to a lack of sleep, such as daytime sleepiness, fatigue, and decreased mental clarity.

There are two main types of insomnia. One is acute insomnia (sometimes called transient insomnia). This type occurs when insomnia symptoms exist over a reasonably short period...