ISI — Insomnia Severity Index

The ISI is the brief sleep measure that matters most for tracking treatment response. Seven items, two-week window, summed 0–28. It’s the dominant outcome instrument for Cognitive Behavioural Therapy for Insomnia (CBT-I) and is short enough to administer every two to four weeks during active treatment.

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What it measures

Insomnia severity along three dimensions:

• Difficulty falling asleep, staying asleep, and waking too early
• Satisfaction with current sleep pattern
• Functional impairment during the day (interference with daily functioning, noticeability to others, distress)

Each item is rated 0–4 over the past two weeks. The sum is the total ISI score.

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When to send it

• Intake whenever insomnia is a presenting concern
• Every 2–4 weeks during CBT-I or any sleep-focused work
• Pre/post for psychoeducation + sleep-hygiene interventions
• As a follow-up after a high PSQI Global score — ISI gives you the severity band on a tighter timeframe

The seven items take 2–3 minutes. Most clients fill it in async between sessions.

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Scoring and severity cutoffs

Simple sum of all seven items, range 0–28. Severity bands surface in the live-scoring pill the moment your client submits: The ≥15 cutoff is the standard threshold for clinical insomnia and the common gate for CBT-I or sleep-clinic referral. Morin (2011) suggests a ≥10 cutoff for community-screening sensitivity if you’re using ISI as the first pass before a more detailed assessment.

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Tracking change

A 6-point drop in the total is the published minimal clinically important difference for CBT-I response (Morin et al. 2011). Rivet’s longitudinal view shows the score trajectory across administrations so the change is visible at a glance.

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ISI vs PSQI

Both are free, both are standard in CBT-I, and they are not interchangeable. The ISI asks seven questions about the last two weeks and is scored as a single insomnia-severity number. That makes it the practical treatment-response measure — short enough to repeat often, with a published threshold at 15 for clinical insomnia. The PSQI asks about the last month across seven components — quality, latency, duration, efficiency, disturbances, medication, daytime dysfunction. It is the better instrument for working out what kind of sleep problem you’re looking at, and a score above 5 is a reasonable trigger to follow up with the ISI or a sleep-medicine referral. It’s also more work: several of its components need arithmetic done from the published scoring sheet. Common pattern — PSQI to characterise the problem at assessment, ISI to track it week to week.

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Is it free to use?

Yes. Free clinical use, per Bastien and colleagues.

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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. Original instrument: Morin, C. M. (1993). Insomnia: Psychological Assessment and Management. New York: Guilford Press. Free clinical use.

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When not to use it

ISI is severity-focused, not diagnostic — it tells you how bad the insomnia is, not what’s driving it. For sleep-disorder differential screening (apnea, restless legs, circadian rhythm disorders), use the PSQI or refer to a sleep-medicine workup. For acute insomnia in the context of a recent crisis, the 2-week window may not yet reflect the current picture — re-administer once two weeks of the current pattern have passed.

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