Screening for clinical insomnia in primary care and psychiatric settings.
Evaluating the nature, severity, and impact of insomnia over the past 2 weeks.
Measuring treatment response to pharmacotherapy or Cognitive Behavioral Therapy for Insomnia (CBT-I).
Differentiating idiopathic insomnia from psychophysiological or comorbid sleep disturbances.
Section 2
Formula & Logic
Scoring Component
The ISI comprises 7 items assessing: sleep onset, sleep maintenance, early morning awakening, sleep satisfaction, interference with daytime functioning, noticeability of impairment by others, and distress caused by sleep problems.
Severity Thresholds
Score 0–7
No clinically significant insomnia
Score 8–14
Subthreshold insomnia
Score 15–21
Clinical insomnia (moderate severity)
Score 22–28
Clinical insomnia (severe)
Section 3
Pearls/Pitfalls
Distress vs. Duration
The ISI is unique because it clinical weight to the patient's "distress" and "impairment" due to sleep, not just the minutes of wakefulness. This aligns with the DSM-5 criteria for Insomnia Disorder.
Clinical Pearls
A change of 6 points or more is generally considered a clinically meaningful response to treatment.
If the score is high but the "Noticeability" item is low, the patient may be masking their symptoms or have high resilience, but still requires treatment.
Always screen for sleep apnea even if ISI is high; treating insomnia without addressing OSA can be ineffective.
Section 4
Next Steps
Treatment Pathway
01
Score 8–14: Provide sleep hygiene education and stimulus control instructions.
02
Score ≥ 15: First-line recommendation is CBT-I (Cognitive Behavioral Therapy for Insomnia).
03
Severe Score (22–28): Consider short-term pharmacological adjuncts while initiating CBT-I to provide immediate relief.
Section 5
Evidence Appraisal
Primary Reference
Validation of the Insomnia Severity Index as an outcome measure for insomnia research
Bastien CH et al. • Sleep Medicine. 2001;Vol 2, Issue 4. pp. 297-307. Established the psychometric properties of the ISI.
Section 6
Literature
Charles M. Morin
Developed by Dr. Charles Morin and colleagues. Morin is a preeminent figure in sleep medicine and was instrumental in developing the evidence base for CBT-I.
