What is the Insomnia Severity Index?

Written by
Dr. R. Y. Langham

Medically Reviewed by
Dr Katherine Hall

“Insomnia is an indication, not a chaos. It’s like ache. You’re not going to provide a patient ache medicine without figuring out what’s reasoning the pain.”

~Judith Owens

Can’t sleep? You’re not alone.

Insomnia is a common sleep disorder that makes it hard for you to fall or stay asleep at night, causes you to wake-up frequently throughout the night, awaken too early, have a hard time falling back asleep, and/or experience non-restorative or poor sleep quality, causing you to feel overly tired, irritable, and groggy the next morning. Insomnia is a prevalent health complaint that is often difficult to reliably evaluate.

Even though insomnia is quite popular, it is one of the most dismissed and untreated sleep disorders, primarily because there aren’t many reliable diagnostic sleep tools on the market. The good news is there is one effective and reliable tool that can assess your sleep issues – the Insomnia Severity Index. The Insomnia Severity Index can help your doctor properly diagnose your sleep problem so you can get a good night’s rest.

What is the Insomnia Severity Index?

Dr. Charles M. Morin, Université Laval (Canada) psychology professor and leading expert of sleep issues, developed the Insomnia Severity Index (ISI), a screening tool, to evaluate insomnia. The ISI is the universal “go-to” clinical and observational assessment tool used in the study of insomnia and its treatments.

Why Was This Index Developed?

The ISI was developed to help doctors screen for insomnia and other sleep disorders. It was designed to be a self-report tool, in which individuals assess their own level of “sleeplessness.” The goal of the Index is to help doctors better understand the nature of insomnia so more effective treatments can be developed. However, it is important to also understand that the ISI was not created to be a diagnostic tool; rather, its aim is to be an aid or supplemental resource in the diagnostic process.

Content

Part 1

What is the Purpose of the Insomnia Severity Index (ISI)?

Part 2

How Is the Index Administered?

Part 3

How is the Index Scored?

Part 4

Summary

What is the Purpose of the Insomnia Severity Index (ISI)?

The ISI was created to be a quick screening tool for “sleeplessness” and insomnia. It involves a 7-item questionnaire (Likert-type scale) that asks you to identify your symptoms and rate the degree and nature of your “sleeplessness.”

The questions are subjective, in nature, and the answers stem from your perception of your sleep quality, symptoms, severity and frequency of your sleep issues, overall satisfaction with your sleep quality (sleep/wake cycles, patterns, etc.), the degree at which your “sleeplessness” disrupts your daily functioning, your level of fear that others will detect that your insomnia, and the amount of stress and distress you experience because of your “sleeplessness.”

Who is the Insomnia Severity Index For?

The ISI was created for insomniacs between the ages of 17 and 84. It has been especially helpful for those suffering from “sleeplessness” stemming from cancer, fibromyalgia, lupus, muscle or joint disorders, depression, and/or anxiety.

How Is the Index Administered?

The ISI is usually uses a paper-and-pencil format. However, other administration forms are also available, such as by a clinician, from the info you provided during your clinical intake, and/or from the info provided by your partner or parent during a clinical interview. The administration form is important because it provides your doctor with data on who you are, your symptoms, and possible triggers.

How Long Does It Take to Complete the Insomnia Severity Index?

The ISI can be completed in about 5 minutes. It is a self-report scale completed by you, the participant.

What Questions are asked on the Index?

Rate the current (within the last 2 weeks) severity of your insomnia problem(s).
How satisfied are you with your current sleep patterns?
How dissatisfied are you with your current sleep patterns?
How noticeable do you think your sleep issues are to others?
Are your sleep issues (insomnia) negatively impacting your daily functioning (i.e., causing daytime fatigue, triggering mood swings or lowering your mood, interfering with your ability to function at work or complete daily tasks, causing concentration or memory issues, etc.). If so, to what extent?
How would you rate your current quality of life?
How worried or distressed are you about your current sleep problems?

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How is the Index Scored?

Because the ISI is a self-reported scale, you are tasked with rating your response to each question using a Likert-type answer format. Each response should fall between 0 and 4, where higher scores (4) mean you are most likely experiencing acute insomnia. Your scores are then analyzed and compared to your scores during various stages of treatment and the scores of other participants.

It is important to note, however, that Dr. Charles M. Morin, the creator of the ISI, admits that the “cut-off scores” have not been validated or standardized. Regardless, Dr. Morin and his colleagues have provided some guidelines on analyzing and interpreting the results.

For instance, a total score between 0-7 suggests that you are not suffering from “clinically-significant insomnia.” While a total score 8-14 suggests that you are at the “sub-threshold of insomnia.” A score 15-21 suggests that you have “mild-to-moderate insomnia.” And, a score 22-28 suggests that you have “severe insomnia.”

Is the Insomnia Severity Index Valid and Reliable?

Yes, this index is valid and reliable.

Experts have found that the ISI is a reliable and valid instrument for identifying insomnia in the general population. Studies also indicate that the ISI is a sensitive sleep scale used to pinpoint insomnia symptoms. Thus, ISI has “officially” been deemed a sound tool to measure the perceived severity of insomnia.

Researchers suggest that the ISI is a clinically useful and effective screening instrument designed to measure the outcome of various insomnia treatments. In fact, a 2001 psychometric study found that the internal consistency of the ISI was .74 and that the consistency amongst questions was .36 to .54. These totals indicate that both the structure and questions are valid and reliable. Similarly, a 2017 study found that test-reliability was excellent.

Summary

Being unable to sleep can wreak havoc on your mood, self-esteem, tolerance and patience levels, performance, productivity, and overall health. Thankfully, you don’t have to suffer with “sleeplessness” indefinitely – there are tools that can help pinpoint why you’re unable to fall and stay asleep throughout the night. One of the most reliable tools is the Insomnia Severity Index. This Index can provide your doctor with deeper insight into your “sleeplessness,” so you can get some much-needed zzz.

References

Bastien, C. H., Vallières, A., & Morin, C. M. (2001). Validation of the insomnia severity index as an outcome measure for insomnia research. Sleep Medicine, 2, 297–307. Retrieved from https://pubmed.ncbi.nlm.nih.gov/11438246/
My Health Vet. (2021). Insomnia severity index. Retrieved from https://www.myhealth.va.gov/mhv-portal-web/insomnia-severity-index
Perelman School of Medicine. (2021). Insomnia severity index (ISI). University of Pennsylvania. Retrieved from https://www.med.upenn.edu/cbti/assets/user-content/documents/Insomnia%20Severity%20Index%20(ISI).pdf
Morin, C. M. (n.d.). Insomnia severity index. Mapi Research Trust. Retrieved from https://mapi-trust.org/questionnaires/isi/#description
Veqar, Z. & Hussain, M. E. (2017). Validity and reliability of insomnia severity index and its correlation with Pittsburgh sleep quality index in poor sleepers among Indian university students. Int J Adolescent Med Health, 32(1). Retrieved from https://pubmed.ncbi.nlm.nih.gov/28063259/
Somnus Therapy. (2021). Sleep therapy at home. Retrieved from https://somnustherapy.com/
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Chahoud, M., Chahine, R., Salameh, P., & Sauleau, E. A. (2017). Reliability, factor analysis and internal consistency calculation of the insomnia severity index (ISI) in French and in English, amongst Lebanese adolescents. eNeurological Science, 7, 9-14. Retrieved from https://pubmed.ncbi.nlm.nih.gov/29260018/
Mayo Clinic. (2021). Insomnia. Retrieved from https://www.mayoclinic.org/diseases-conditions/insomnia/symptoms-causes/syc-20355167
Smith, M. T. & Wegner, S. T. (2003). Measures of sleep: The insomnia severity index, medical outcomes study (MOS) sleep scale, Pittsburgh sleep diary (PSD), and Pittsburgh sleep quality index (PSQI). Arthritis Care and Research, 49(55), S184-S196. Retrieved from https://onlinelibrary.wiley.com/doi/10.1002/art.11409
Peters, B. (2020). Causes, symptoms, and treatment of short-term or acute insomnia. Very Well Health. Retrieved from https://www.verywellhealth.com/what-is-acute-insomnia-3014757
Michaud, A. L., Zhou, E. S., Chang, G., & Recklitis, C. J. (2021). Validation of the insomnia severity index (ISI) for identifying insomnia in young adult cancer survivors: comparison with a structured clinical diagnostic interview of the DSM-5 (SCID-5). Sleep Medicine, 81, 80-85. Retrieved from https://doi.org/10.1016/j.sleep.2021.01.045