insomnia

Meaning: Insomnia is a dyssomnia, a disorder of the amount, quality, or timing of sleep. The person has trouble falling asleep, staying asleep, or going back to sleep after waking too early, even when there is time to sleep. The result is daytime sleepiness, poor concentration, and irritability. Common contributors include stress, anxiety, depression, irregular schedules, and stimulants such as caffeine. Raised arousal at bedtime works against the processes that normally bring on sleep.

On the MCAT: A vignette describes someone who lies awake, wakes repeatedly, or wakes far too early, and you must name the disorder. The wrong answers are usually other sleep disorders: narcolepsy (sudden sleep attacks in the day, with REM sleep intruding into waking), sleep apnea (breathing repeatedly stops during sleep and fragments it), and night terrors or sleepwalking (arousals from deep non-REM sleep). You may also be asked about behavioral treatment, such as good sleep hygiene: a regular schedule, less caffeine, and a calm bedtime routine.

Common confusion: Insomnia is not the same as sleep deprivation. A sleep-deprived person lacks sleep because of limited time or choice, while a person with insomnia cannot sleep despite the opportunity. Do not confuse it with narcolepsy either: insomnia is too little sleep at night, and narcolepsy is unwanted sleep during the day.