Insomnia Severity Index (ISI)

Assess Your Sleep with the Insomnia Severity Index (ISI)

Poor sleep can weigh heavily on your daily life, and the Insomnia Severity Index (ISI) is a practical tool to help you understand it better. Crafted by sleep experts, this concise questionnaire gauges the severity of your insomnia symptoms over the past two weeks. As a Sydney psychologist working with sleep challenges, I find it a valuable starting point. You can try the test below or read on for more details at your own pace.

Why Use the Insomnia Severity Index

The Insomnia Severity Index (ISI) is a straightforward way to assess your sleep struggles, especially since insomnia affects more people than you might think. Research shows that 10–15% of adults deal with chronic insomnia, with many more facing occasional difficulties that sap energy or dampen mood. Before tools like the ISI, these issues often slipped under the radar without an easy way to measure them. The ISI provides:

Ease of Use: It takes just 3–5 minutes to complete, slotting into any day.
Clear Feedback: Your score shows how severe your insomnia might be, offering a nudge toward action if needed.
Support for Understanding: As a Sydney psychologist, I use the ISI alongside sleep diaries to unpack sleep patterns and guide treatment when insomnia looms large.

It’s a gentle way to check in on your sleep, whether you’re exploring solo or considering a deeper dive with a professional.

Take the Insomnia Severity Index Test

To ensure the most accurate Insomnia Severity Index Score Interpretation:
Reflect honestly on sleep experiences over the past two weeks.
Answer each question carefully and independently.
Retake the test periodically under similar conditions to reliably track changes over time.

Use the ISI self-assessment below to measure the severity of your insomnia symptoms. This test provides immediate scoring and interpretation based on your responses.

How is the Insomnia Severity Index Questionnaire Scored? - Insomnia Severity Index Score Interpretation

0–7 (No clinically significant insomnia): Your sleep patterns are within a normal range. No immediate intervention is necessary.
8–14 (Subthreshold insomnia): Mild sleep disturbances are present, but they may not require treatment unless symptoms worsen.
15–21 (Moderate insomnia): You may experience difficulties with falling or staying asleep, impacting daily life. Consider consulting a psychologist or sleep specialist.
22–28 (Severe insomnia): Persistent sleep issues are significantly affecting your quality of life. Seeking professional help is strongly recommended.

The Science and Development of the ISI

The Insomnia Severity Index (ISI) is rooted in solid sleep research, making it a reliable measure of insomnia severity. Developed in the late 1990s by Dr. Charles Morin and his team at Université Laval in Quebec, it was first published in 2001 to meet a clinical and research need. At the time, insomnia was gaining recognition as a standalone issue, but tools to assess its impact were scarce. The ISI stepped in to fill that gap.

Its seven questions—covering sleep onset, maintenance, satisfaction, and daytime effects—were designed using clinical expertise and aligned with the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for insomnia. Before the ISI, broader tools like the Pittsburgh Sleep Quality Index existed, but they weren’t specific to insomnia’s severity or responsive to treatment changes. The ISI’s focus and brevity made it a hit, and it’s since been validated worldwide for both screening and tracking progress.

How Accurate and Reliable is the Insomnia Severity Index (ISI)?

The Insomnia Severity Index (ISI) is widely recognized as one of the most reliable and accurate tools available for evaluating insomnia symptoms. Numerous scientific studies have demonstrated its effectiveness, making it a trusted choice among healthcare providers and researchers worldwide.

Validity: Does the ISI Measure What It’s Supposed To?

Validity refers to how effectively a test measures what it claims to measure. Research has repeatedly confirmed the ISI’s strong validity:

Construct Validity: The ISI accurately reflects insomnia severity by correlating closely with other established measures of sleep quality, sleep diaries, and clinical diagnoses by sleep specialists.
Clinical Validity: The ISI has been thoroughly tested across different groups of individuals, including those with diagnosed insomnia, general populations, and people with other health conditions. It consistently distinguishes between different levels of insomnia severity, supporting its clinical usefulness.

Reliability: Can You Trust the ISI Results?

Reliability describes how consistent a test is over time and across different contexts:

Test-Retest Reliability: The ISI consistently produces similar results when the same individual takes the test multiple times within short intervals, assuming no significant changes in their sleep patterns.
Internal Consistency: The questions within the ISI align closely together, meaning they reliably measure the same underlying issue—insomnia severity.

Practical Relevance: Why the ISI Matters

Because the ISI is both reliable and valid, healthcare providers trust it to:

Quickly identify individuals who may benefit from insomnia treatment.
Track changes in sleep patterns over time, helping to monitor how effective treatment interventions are.
Enhance communication between patients and clinicians by clearly quantifying insomnia severity.

In short, the ISI isn’t just another questionnaire; it’s a proven, scientifically-backed tool that provides real, actionable insights into sleep health.

Who Should Use the Insomnia Severity Index?

The Insomnia Severity Index Questionnaire is valuable for anyone concerned about their sleep patterns, including:

- Individuals experiencing difficulty falling or staying asleep regularly.
- People noticing daytime impairment related to poor sleep quality.
- Individuals who want to track sleep improvements during treatment.
- Healthcare professionals who require a quick, reliable method to evaluate insomnia in patients.

Comparing the ISI with Other Sleep Measures

The Insomnia Severity Index (ISI) is one of several tools for assessing sleep, each with its own angle. Here’s how it stacks up:

ISI: With 7 questions, it takes 3–5 minutes and scores from 0 to 28, with scores above 14 suggesting insomnia. It zeroes in on insomnia severity and impact over two weeks, perfect for tracking treatment.
Sleep Condition Indicator (SCI): This 8-question tool takes 2–3 minutes and scores from 0 to 32, with scores below 16 indicating possible insomnia. It’s quick and tied to modern DSM-5 criteria, great for screening.
Pittsburgh Sleep Quality Index (PSQI): With 19 questions over 5–10 minutes, it scores from 0 to 21, where scores above 5 signal poor sleep. It’s broader, assessing overall sleep quality over a month.
Athens Insomnia Scale (AIS): An 8-question measure taking 3–5 minutes, it scores from 0 to 24, with scores above 6 pointing to insomnia. It emphasizes symptom intensity over a month.

The ISI stands out for its focus on insomnia’s severity, while the SCI is faster, the PSQI broader, and the AIS intensity-driven. In my practice, I often pair the ISI with sleep diaries for a fuller view.

Limitations and Criticisms of the ISI

The Insomnia Severity Index (ISI) is a strong tool, but it has its limits worth noting when reviewing your score:

Not a Full Diagnosis: The ISI screens for insomnia severity but doesn’t cover all diagnostic details—like whether sleep issues persist despite enough time to sleep, per DSM-5. It can’t rule out other causes either, so a low score needs more context.
Focused Scope: Its seven questions hit key insomnia points, but it skips specifics like early waking patterns or sleep variability. It’s sharp but not exhaustive.
Your Perception: It’s based on your recall of the past two weeks, which can shift depending on how you feel. You might overestimate a bad night, but that’s part of how insomnia is defined—your experience matters.
Other Causes: A high score might reflect sleep apnea or stress, not just insomnia. The ISI flags the problem but doesn’t diagnose the source.
Early Testing: It was first studied with insomnia patients, which might tweak its accuracy for general use. Later research broadened its reach, but it’s strongest in clinical settings.

Still, its precision, speed, and research backing make it valuable, especially when teamed with follow-up tools or a professional chat.

When to Consult a Sleep Specialist or Psychologist

Consider scheduling a consultation with a sleep specialist or psychologist if you:

Regularly score in the moderate or severe range on the ISI.
Experience persistent daytime fatigue, mood disturbances, or difficulty functioning at work or home.
Notice worsening sleep problems despite lifestyle changes or initial treatment efforts.

Frequently Asked Questions (FAQ)

What is the Insomnia Severity Index used for?

The Insomnia Severity Index (ISI) is a self-assessment questionnaire designed to measure the severity and impact of insomnia symptoms. Specifically, it helps individuals understand how significantly their sleep issues are affecting their daily functioning and overall quality of life. Healthcare professionals and researchers frequently use the ISI to evaluate insomnia severity, guide treatment decisions, and monitor improvements or changes in sleep patterns over time.

How accurate is the ISI?

The Insomnia Severity Index is a scientifically validated tool with robust evidence supporting its reliability and accuracy. Numerous research studies have consistently demonstrated its effectiveness in accurately measuring insomnia severity. Due to its strong internal consistency and test-retest reliability, the ISI is trusted by clinicians and researchers to provide a reliable measure of insomnia symptoms and treatment outcomes.

What does my ISI score mean?

Your Insomnia Severity Index score provides a clear interpretation of the severity of your insomnia symptoms. Scores range from 0 to 28 and fall into specific categories:

0–7 (No clinically significant insomnia): Your sleep patterns are within a normal range and generally do not require professional intervention.
8–14 (Subthreshold insomnia): Mild sleep issues are present, potentially affecting your daily activities or quality of life but may not require immediate treatment.
15–21 (Moderate insomnia): Indicates moderate severity, suggesting significant sleep disturbances affecting daily functioning, recommending consultation with a psychologist or sleep specialist.
22–28 (Severe insomnia): Suggests severe insomnia, significantly impairing your quality of life. Professional evaluation and intervention are strongly advised.

Can the ISI diagnose insomnia?

The Insomnia Severity Index is not a diagnostic instrument. Instead, it’s a screening questionnaire that identifies individuals who may benefit from a thorough clinical evaluation. If your ISI score indicates moderate or severe insomnia, this suggests that further evaluation by a healthcare provider, such as a clinical psychologist or sleep specialist, is recommended to formally diagnose insomnia and discuss potential treatment options.

Should I take the ISI test regularly?

Regularly completing the Insomnia Severity Index can be beneficial, especially if you experience ongoing sleep problems or are actively participating in insomnia treatment. During active treatment or when making lifestyle changes, retaking the ISI every 2–4 weeks helps monitor your progress effectively. Once your sleep issues improve or stabilize, you may switch to quarterly assessments (every three months) to continue tracking your sleep health and promptly address any recurring symptoms.

How often should I retake the Insomnia Severity Index?

If you’re actively working on improving your sleep through treatment or lifestyle changes, it’s recommended to retake the Insomnia Severity Index every 2–4 weeks to effectively track your progress. Once your sleep patterns stabilize or improve significantly, you can move to quarterly assessments (every 3 months) to monitor long-term sleep quality and promptly identify any recurrence of insomnia symptoms. Regular use helps ensure that any necessary adjustments to your sleep strategies or treatment plan can be made promptly.

Next Steps

If your ISI score suggests moderate to severe insomnia, consider speaking with a clinical psychologist or sleep specialist for a comprehensive assessment and treatment options.

Explore More Insomnia and Sleep Tools

Investigate other validated measures to assess insomnia, sleep quality, sleep hygiene, and factors like daytime sleepiness or beliefs about slepp. Track patterns with our sleep diary or visit our assessment hub for a full overview of insomnia assessment.

Insomnia Severity Index (ISI) – Gold standard self-report tool for insomnia severity over two weeks.
Pittsburgh Sleep Quality Index (PSQI) – Assesses overall sleep quality and disturbances over a month.
Athens Insomnia Scale (AIS) – Broad sleep quality, not just insomnia.
Sleep Condition Indicator (SCI) – Screens insomnia per DSM-5 with a focus on sleep satisfaction.
Epworth Sleepiness Scale (ESS) – Guages daytime sleepiness across eight everyday situations.
Sleep Hygiene Index (SHI) – Identifies sleep-disruptive habits and behaviours affecting rest.
Dysfunctional Beliefs and Attitudes about Sleep (DBAS-16) – Probes unhelpful beliefs influencing sleep difficulties.
Pre-Sleep Arousal Scale (PSAS) – Measures cognitive and physical arousal before bedtime.

Assessment Hub: Central hub for all sleep and insomnia measures.
Sleep Diary: Records daily sleep habits for personalised insights.

References for the Insomnia Severity Index (ISI)

Morin, C. M., Belleville, G., Bélanger, L., & Ivers, H. (2011). The Insomnia Severity Index: Psychometric indicators to detect insomnia cases and evaluate treatment response. Sleep, 34(5), 601-608. https://doi.org/10.1093/sleep/34.5.601
This article demonstrates the ISI’s effectiveness in accurately identifying insomnia cases and assessing the outcomes of treatment.

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 foundational study validates the ISI as a reliable and valid tool for evaluating insomnia severity in both clinical and research settings.

Gagnon, C., Bélanger, L., Ivers, H., & Morin, C. M. (2013). Validation of the Insomnia Severity Index in primary care. Journal of the American Board of Family Medicine, 26(6), 701-710. https://doi.org/10.3122/jabfm.2013.06.130064
This study provides strong evidence supporting the ISI’s use in primary care settings, highlighting its practical value in general medical practice.