The Insomnia Severity Index is a 7 question assessment used to evaluate the severity of insomnia. Respondents rate their sleep difficulties over the past 2 weeks on a scale of 0-4 for each question. Scores are added up to determine the total: 0-7 indicates no clinically significant insomnia, 8-14 is subthreshold insomnia, 15-21 is moderate clinical insomnia, and 22-28 is severe clinical insomnia. The assessment evaluates difficulties falling asleep, staying asleep, waking too early, satisfaction with sleep patterns, noticeability of sleep problems to others, levels of worry about sleep, and interference of sleep problems with daily functioning.