The Insomnia Severity Index: What Your Score Means
The Insomnia Severity Index is a seven-question scale scored from 0 to 28 that measures how much insomnia is disrupting your sleep and days. Clinicians use it to screen for cases and to track whether treatment is moving the needle.
Key takeaways
- Each ISI item is rated 0 to 4, covering difficulty falling asleep, staying asleep, and early waking, plus satisfaction, worry, and daytime impact, for a total from 0 to 28.
- The standard interpretation bands the score: 0 to 7 no clinically significant insomnia, 8 to 14 subthreshold, 15 to 21 moderate clinical insomnia, and 22 to 28 severe.
- Validation work in a population-based sample showed the ISI separates people with clinical insomnia from good sleepers, and it tracks change across CBT-I and medication trials.
- Research studies commonly use a cutoff of 10 or higher to flag clinical insomnia, and scores below 8 after treatment count as remission in CBT-I trials.
- The ISI measures severity, not cause; a high score still needs a clinician's evaluation for apnea, restless legs, medication effects, or mood disorders before treatment choices are locked in.
| What the band signals | Sensible next step | |
|---|---|---|
| 0-7 | No clinically significant insomnia | Keep routines steady; retest if worry persists |
| 8-14 | Subthreshold insomnia | Watch and adjust habits; escalate if scores drift upward |
| 15-21 | Moderate clinical insomnia | Warrants evaluation; CBT-I is the guideline first-line |
| 22-28 | Severe clinical insomnia | Structured treatment and a clinician's assessment now |
What This Guide Covers
The Insomnia Severity Index is a seven-question scale scored from 0 to 28 that measures how much insomnia is disrupting your sleep and days. Clinicians use it to screen for cases and to track whether treatment is moving the needle. This guide walks you through what matters most, why it happens, and the practical steps with the best support behind them.
First, the foundation: each ISI item is rated 0 to 4, covering difficulty falling asleep, staying asleep, and early waking, plus satisfaction, worry, and daytime impact, for a total from 0 to 28.
Next, the details: the standard interpretation bands the score: 0 to 7 no clinically significant insomnia, 8 to 14 subthreshold, 15 to 21 moderate clinical insomnia, and 22 to 28 severe.
Then, the practical side: validation work in a population-based sample showed the ISI separates people with clinical insomnia from good sleepers, and it tracks change across CBT-I and medication trials.
Another angle worth knowing: research studies commonly use a cutoff of 10 or higher to flag clinical insomnia, and scores below 8 after treatment count as remission in CBT-I trials.
Finally, the big picture: the ISI measures severity, not cause; a high score still needs a clinician's evaluation for apnea, restless legs, medication effects, or mood disorders before treatment choices are locked in.
Frequently Asked Questions
What exactly is insomnia severity index?
The Insomnia Severity Index is a seven-question scale scored from 0 to 28 that measures how much insomnia is disrupting your sleep and days. Clinicians use it to screen for cases and to track whether treatment is moving the needle.
How long until I see improvement?
Most of the strategies in this guide start showing effect within one to two weeks of consistent practice. Supplement- and device-based approaches vary more, so track your nights in a simple sleep diary and judge by weekly trends rather than single nights.
When should I see a doctor?
If the problem lasts more than a few weeks, disrupts your daytime functioning, or comes with warning signs such as breathing pauses, gasping during sleep, chest discomfort, or severe daytime sleepiness, it is time to consult a qualified healthcare professional rather than self-treating.
References
- Bastien CH, Vallières A, Morin CM. Validation of the Insomnia Severity Index as an outcome measure for insomnia research. Sleep Med. 2001;2(4):297-307.
- Morin CM, Belleville G, Bélanger L, Ivers H. The Insomnia Severity Index: psychometric indicators to detect insomnia cases and evaluate treatment response. Sleep. 2011;34(5):601-608.
- StatPearls. Cognitive Behavioral Therapy for Insomnia. NCBI Bookshelf, National Library of Medicine.