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Insomnia Severity Index

A validated 7-question screening tool that measures the severity and impact of insomnia symptoms over the past two weeks.

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Rate each item below on a scale of 0 to 4, reflecting your sleep over the last two weeks.

1.Difficulty falling asleep

2.Difficulty staying asleep

3.Problem waking up too early

4.How satisfied/dissatisfied are you with your current sleep pattern?

5.How noticeable to others do you think your sleep problem is in terms of impairing the quality of your life?

6.How worried/distressed are you about your current sleep problem?

7.To what extent do you consider your sleep problem to currently interfere with your daily functioning?

What This Tool Measures

The Insomnia Severity Index (ISI) measures your subjective perception of insomnia severity across three dimensions: difficulty falling asleep, difficulty staying asleep, and early morning awakening. It also captures how satisfied you are with your current sleep pattern, how much insomnia interferes with your daily functioning, how noticeable your impairment is to others, and how worried or distressed you are about your sleep. Your total score (0 to 28) places your insomnia on a four-level severity scale ranging from "no clinically significant insomnia" to "severe clinical insomnia."

Clinical Background

The ISI was developed by Bastien, Vallieres, and Morin and published in Sleep Medicine in 2001. It was designed to provide a brief, reliable measure of insomnia severity that could be used in both clinical practice and research settings. The original validation study demonstrated strong internal consistency, good test-retest reliability over a two-week interval, and sensitivity to change with treatment.

Since its publication, the ISI has been validated in clinical populations (insomnia patients, cancer patients, chronic pain patients) and community samples across multiple countries and languages. It is one of the most widely used insomnia outcome measures in sleep research. The American Academy of Sleep Medicine (AASM) recommends the ISI as part of insomnia assessment, and it is frequently used in cognitive behavioral therapy for insomnia (CBT-I) treatment trials to track patient progress.

One important consideration: the ISI captures your perception of insomnia severity over the past two weeks, not objective sleep measurements. Perceived sleep quality and objective sleep duration do not always align. This is part of why the ISI is used as a screening and monitoring tool rather than a diagnostic instrument.

Scoring and Severity Levels

Each of the seven questions is rated on a 5-point scale (0 to 4), giving a total score range of 0 to 28. The published severity thresholds:

  • 0 to 7: No clinically significant insomnia. Your sleep difficulties are within the normal range and are unlikely to require clinical intervention.
  • 8 to 14: Subthreshold insomnia. You are experiencing some insomnia symptoms that may benefit from improved sleep habits or monitoring, but they do not yet meet the threshold for a clinical insomnia diagnosis.
  • 15 to 21: Moderate clinical insomnia. Your insomnia symptoms are clinically significant and are likely affecting your daytime functioning. Consider discussing your sleep with a healthcare provider.
  • 22 to 28: Severe clinical insomnia. Your insomnia is severe and is strongly associated with meaningful impairment in daily life. Evaluation by a sleep specialist is recommended.

These thresholds are based on the original Bastien, Vallieres, and Morin (2001) validation study and are consistent with current AASM clinical practice recommendations.

Insomnia and Sleep Apnea

Insomnia and obstructive sleep apnea frequently coexist, a condition known as COMISA (co-morbid insomnia and sleep apnea). Research estimates that 30 to 50 percent of people diagnosed with OSA also experience clinically significant insomnia symptoms. The relationship runs in both directions: apnea events fragment sleep and trigger awakenings that can condition the brain toward hyperarousal, while insomnia-related anxiety about sleep can make it harder to fall asleep with a CPAP mask. People with COMISA tend to have lower CPAP adherence and worse treatment outcomes than those with either condition alone. If your ISI score suggests moderate or severe insomnia and you are also using CPAP, it is worth raising both issues with your provider. Cognitive behavioral therapy for insomnia (CBT-I) combined with CPAP therapy has shown better results for COMISA patients than either treatment alone.

Frequently Asked Questions

What is the Insomnia Severity Index?

The Insomnia Severity Index (ISI) is a validated 7-question self-report questionnaire that measures the perceived severity and impact of insomnia symptoms over the past two weeks. It was developed by Bastien, Vallieres, and Morin in 2001 and is widely used in both clinical practice and research to screen for insomnia and track treatment response.

Can insomnia coexist with sleep apnea?

Yes. The combination of insomnia and obstructive sleep apnea is known as COMISA (co-morbid insomnia and sleep apnea) and affects an estimated 30 to 50 percent of people with OSA. Insomnia can make it harder to tolerate CPAP therapy, and untreated apnea can fragment sleep in ways that mimic or worsen insomnia. Both conditions need to be addressed for effective treatment.

How is the ISI scored?

Each of the seven questions is rated on a scale of 0 (no problem) to 4 (very severe problem), giving a total score range of 0 to 28. Scores of 0 to 7 indicate no clinically significant insomnia, 8 to 14 indicate subthreshold insomnia, 15 to 21 indicate moderate clinical insomnia, and 22 to 28 indicate severe clinical insomnia.

Should I retake the ISI over time?

Yes. The ISI is designed to be sensitive to change, which makes it useful for tracking treatment response. Many clinicians ask patients to complete the ISI before starting treatment and again at follow-up visits. A reduction of 6 or more points is generally considered a clinically meaningful improvement. Retaking the questionnaire every few months can help you and your provider evaluate whether your current approach is working.

Is the ISI the same as a sleep study?

No. The ISI is a subjective screening questionnaire that measures your perception of your insomnia symptoms. A sleep study (polysomnography) is an objective laboratory test that records brain waves, breathing, heart rate, and limb movements during sleep. The ISI can identify insomnia severity and track changes over time, but it cannot diagnose underlying conditions like sleep apnea, periodic limb movement disorder, or narcolepsy. A sleep study is needed for those diagnoses.

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