Brief Description
The Insomnia Severity Index (ISI) measures the severity of both nighttime and daytime components of insomnia and quantifies subjective dimensions of insomnia to assess the nature, severity, and impact of insomnia. The ISI consists of 7 items that cover various aspects of insomnia, including the severity of sleep onset and maintenance difficulties, satisfaction with sleep patterns, interference with daily functioning, and perception of the problem's duration. The ISI serves as a screening and severity assessment tool that can be used to track progress during treatment. Respondents rate the severity of their insomnia and answer questions related to sleep (e.g., “How worried/distressed are you about your current sleep problem?”) on a variety of scales, such as “Not at all Worried” to “Very Much Worried.”
Assessment Administration Type
Self-report
Number of questions
7
Age Range for Administration
17-84
Recommended Frequency of Administration
Every 2 weeks
Summary of Scoring and Interpretations
The ISI contains 7 questions scored on varying 5-point Likert scales with values from 0 (“None,” “Very Satisfied,” “Not at all Noticeable,” “Not at all Worried,” “Not at all Interfering”) to 4 (“Very Severe,” “Very Dissatisfied,” “Very Much Noticeable,” “Very Much Worried,” “Very Much Interfering”). A total score is calculated by summing the item responses and ranges from 0 to 28; higher scores are associated with higher levels of, or more severe, insomnia. See the table below for score interpretations.
Score | Interpretation |
0-7 | No clinically significant insomnia |
8-14 | Sub-threshold insomnia (mild severity) |
15-21 | Clinical insomnia (moderate severity) |
22-28 | Clinical insomnia (severe) |
Blueprint Adjustments
N/A
Clinical Considerations
Estimated completion time: 2-3 minutes.
There is an abbreviated 3-item ISI, found here.
The assessment of insomnia is multidimensional and should ideally include a clinical evaluation and be complemented by self-report questionnaires and daily sleep diaries.
Insomnia is a highly prevalent condition and carries significant burden in terms of functional impairment, health care costs, and increased risk of depression. Identifying clinically significant insomnia is also important to intervene early and reduce morbidity. Thus, reliable and valid instruments are needed to assist investigators and clinicians in evaluating insomnia in various research and clinical contexts.
Citation
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