Insomnia Severity Index Calculator
Free Insomnia severity index Calculator with medically-sourced formulas. Enter your measurements for personalized, accurate health insights.
Reviewed by Rahul Singh, Health & Wellness Specialist
Formula
ISI Total = Sum of 7 items (0-4 each, max 28)
Seven items are rated 0-4: three nighttime symptom items (difficulty falling asleep, staying asleep, early awakening), sleep satisfaction, noticeability of impairment, distress level, and interference with daily functioning. Total 0-7: No insomnia, 8-14: Subthreshold, 15-21: Moderate clinical, 22-28: Severe clinical insomnia.
Worked Examples
Example 1: Moderate Clinical Insomnia Assessment
Problem:A 45-year-old woman rates: Difficulty falling asleep=3, Staying asleep=2, Early waking=2, Satisfaction=3, Noticeable to others=2, Worried=3, Interferes with daily life=2. Calculate ISI.
Solution:Item scores: 3 + 2 + 2 + 3 + 2 + 3 + 2 = 17\nTotal ISI = 17 out of 28\nNighttime symptoms: 3+2+2 = 7/12\nSatisfaction: 3/4\nDaytime impact: 2+3+2 = 7/12\nClassification: Clinical Insomnia (Moderate), score 15-21\nTreatment: CBT-I recommended as first-line therapy.
Result:ISI Score: 17/28 | Clinical Insomnia (Moderate) | CBT-I recommended
Example 2: Post-Treatment Follow-Up Assessment
Problem:After 6 weeks of CBT-I, the same patient re-scores: Falling asleep=1, Staying asleep=1, Early waking=1, Satisfaction=1, Noticeable=0, Worried=1, Interferes=1. Calculate ISI and treatment response.
Solution:Item scores: 1 + 1 + 1 + 1 + 0 + 1 + 1 = 6\nTotal ISI = 6 out of 28\nPre-treatment ISI = 17, Post-treatment ISI = 6\nChange = -11 points (clinically significant: >= 6 point reduction)\nPost-treatment score <= 7 = Remission achieved\nClassification: No Clinically Significant Insomnia
Result:ISI Score: 6/28 | Remission Achieved | 11-point improvement from CBT-I treatment
Frequently Asked Questions
What is the Insomnia Severity Index and how is it scored?
The Insomnia Severity Index (ISI) is a brief, validated self-report questionnaire developed by Dr. Charles Morin in 1993 to assess the nature, severity, and impact of insomnia over the past two weeks. It consists of 7 items, each rated on a scale of 0 to 4, producing a total score ranging from 0 to 28. The first three items assess the severity of sleep onset difficulty, sleep maintenance difficulty, and early morning awakening. The remaining four items evaluate sleep satisfaction, interference with daily functioning, noticeability of impairment to others, and level of distress caused by the sleep problem. The ISI is widely used in both clinical practice and research settings.
How are ISI scores categorized into severity levels?
ISI total scores are divided into four clinical categories that guide treatment decisions. A score of 0 to 7 indicates no clinically significant insomnia, meaning the individual has normal sleep patterns or very minor sleep complaints that do not require treatment. A score of 8 to 14 represents subthreshold insomnia, where some sleep difficulties exist but may not meet full diagnostic criteria for an insomnia disorder. A score of 15 to 21 indicates clinical insomnia of moderate severity, warranting active treatment intervention. A score of 22 to 28 represents severe clinical insomnia requiring comprehensive treatment. These cutoffs have been validated against clinical interviews and polysomnography data.
What causes chronic insomnia and who is at risk?
Chronic insomnia has multiple contributing factors often explained by the 3P model: predisposing, precipitating, and perpetuating factors. Predisposing factors include genetic tendency toward hyperarousal, female sex, advancing age, and personality traits such as perfectionism and neuroticism. Precipitating factors are stressful life events, medical illness, pain, medication changes, or major schedule disruptions that trigger the initial insomnia episode. Perpetuating factors are maladaptive behaviors adopted in response to insomnia, such as spending excessive time in bed, irregular sleep schedules, napping, caffeine use, and anxious rumination about sleep. Approximately 10 to 15 percent of adults worldwide suffer from chronic insomnia disorder, with women affected twice as often as men.
What is cognitive behavioral therapy for insomnia (CBT-I)?
Cognitive Behavioral Therapy for Insomnia (CBT-I) is the first-line treatment recommended by the American College of Physicians, the American Academy of Sleep Medicine, and the European Sleep Research Society for chronic insomnia disorder. CBT-I typically consists of 4 to 8 sessions and includes multiple components: sleep restriction therapy (limiting time in bed to match actual sleep time), stimulus control (strengthening the bed-sleep association), sleep hygiene education, cognitive restructuring (addressing unhelpful beliefs about sleep), and relaxation training. Research consistently shows that CBT-I produces sustained improvements equal to or greater than sleep medications, with typical ISI score reductions of 8 to 10 points and treatment response rates of 70 to 80 percent.
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy