Insomnia, also known as sleeplessness, is a  31  disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep  32  desired. Insomnia is typically followed by daytime sleepiness, low energy,  33 , and a depressed mood. It may result in an increased risk of motor vehicle collisions, as well as problems  34 . Insomnia can be short term, lasting for days or weeks, or long term, lasting more than a month. The concept of the word insomnia has two possibilities: insomnia disorder and insomnia symptoms, and many  35  of randomized controlled trials and systematic reviews often underreport on which of these two possibilities the word insomnia refers to.

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