Insomnia

Insomnia is persistent difficulty falling asleep, staying asleep, or waking too early — with sleep that feels unrefreshing and causes daytime problems.

Definition

Insomnia is a sleep complaint characterized by trouble initiating or maintaining sleep, or early-morning awakening, accompanied by distress or impairment (fatigue, mood changes, concentration problems). Short-term insomnia is common during stress; chronic insomnia lasts longer and often needs a structured approach. The Insomnia Severity Index (ISI) screens symptom severity but does not replace medical evaluation for sleep disorders.

What it can feel like

  • Lying awake for a long time before falling asleep.
  • Waking repeatedly during the night.
  • Waking earlier than intended and being unable to return to sleep.
  • Feeling exhausted, irritable, or foggy during the day because of poor sleep.

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Frequently asked questions

How much sleep trouble counts as insomnia?

Occasional bad nights are common. Insomnia is more concerning when sleep problems are frequent, lasting, and affect daytime functioning.

Can anxiety or depression cause insomnia?

Yes. Mood and anxiety symptoms often disrupt sleep, and poor sleep can worsen mood — a two-way relationship.

Is an ISI score a sleep diagnosis?

No. The ISI estimates insomnia severity for education and discussion with a clinician. Other sleep conditions may need separate assessment.

Sources

  • Bastien CH, et al. Insomnia Severity Index (ISI)
  • American Academy of Sleep Medicine — insomnia overview
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