The Insomnia Severity Index (ISI) is a brief, self-report questionnaire that assesses the severity of insomnia symptoms. It is widely used in both clinical and research settings to evaluate the impact of insomnia on daily functioning and quality of life. The ISI consists of seven items that measure different aspects of insomnia, including sleep onset, sleep maintenance, waking up too early, satisfaction with sleep pattern, interference with daily functioning, noticeability of impairments, and distress caused by sleep difficulties.
