Insomnia Severity Index

ISI

health sciencespsychologyLicensed: permission required

Permission: Licensed: permission required. Obtain permission from the copyright holder before using it in a study.

A 7-item self-report measure of the nature, severity, and impact of insomnia over the past two weeks, widely used as an outcome measure in insomnia research.

Items

Response format

5-point severity scale (0-4)

Version

1.0

Ready-to-cite methods sentence

Insomnia severity was measured with the Insomnia Severity Index (ISI; Bastien et al., 2001), a 7-item scale with high internal consistency (α = .90 and .91 in community and clinical samples; Morin et al., 2011); scores of 8, 15, and 22 mark subthreshold, moderate, and severe insomnia.

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Permission required

Importing ISI into a Surveyor study is disabled: Folio holds the instrument’s metadata, not a license to pass on its wording. The citation, scoring and reliability details on this page are free to use and cite.

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Reliability & validation

Source

Morin et al., 2011

Validation population

Adults in insomnia research (Bastien et al., 2001; Morin et al., 2011)

Cronbach's α

0.9

Known limitations

A self-report screening/outcome measure rather than a diagnostic or objective (polysomnographic) assessment; cutoffs differ slightly between community and clinical samples.

Original citation

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(4), 297-307.

https://doi.org/10.1016/S1389-9457(00)00065-4

This instrument is licensed. Folio does not distribute its item wording. Obtain permission from the copyright holder before using it in your study.

Questions researchers ask

What does the ISI measure?

A 7-item self-report measure of the nature, severity, and impact of insomnia over the past two weeks, widely used as an outcome measure in insomnia research.

How many items does the ISI have?

The Insomnia Severity Index (ISI) has 7 items.

Is the ISI free to use?

The ISI is licensed. You must obtain permission from the copyright holder before using it in a study. Folio does not distribute its item wording without that permission.

Is the ISI reliable?

Validation studies report Cronbach's α of 0.9 (Morin et al., 2011). See the reliability section for the population studied and full statistics.

Who developed the ISI, and how do I cite it?

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(4), 297-307. https://doi.org/10.1016/S1389-9457(00)00065-4

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Library entry verified September 2026. Metadata is provided for reference; item wording is available inside Folio Surveyor, subject to each instrument's licensing.