Insomnia Severity Index

ISI

health sciencespsychologyFree for research use

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); scores of 8, 15, and 22 mark subthreshold, moderate, and severe insomnia.

Citing this in a methods section? This scale spans more than one discipline, so the style depends on where you publish — see the APA 7 or Vancouver guides, or compare all six citation styles.

Reliability & validation

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

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 free to use for non-commercial academic research. You don't need to pay a license fee, but you should always cite the original publication.

Is the ISI reliable?

Validation studies report Cronbach's α of 0.9. 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

Reference only

Folio has verified the citation and methods metadata for this scale, but does not hold confirmed item wording or scoring to import into Surveyor.

Save ISI

Or track new research mentioning ISI as it publishes

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