A Psychometric Evaluation of the Insomnia Severity Index (ISI) Questionnaire in Swedish Adolescents

Abstract

Insomnia is a sleep disorder with a high prevalence in teenagers, which leads to suffering and an increased risk of future health problems. The Insomnia Severity Index (ISI) is a validated and well-researched self-report questionnaire that aims to quantify insomnia and its severity in adults. It is used in insomnia research and has been translated into many languages, including Swedish. The psychometric properties of the ISI have been thoroughly investigated for adults and to some extent on teenagers abroad, but a psychometric evaluation of a Swedish translation of the ISI with young people in Sweden is still missing. The approach of this study was to evaluate the psychometric properties of the ISI in a sample of Swedish teenagers. A cross-sectional study with data from 184-205 participants from a larger study was conducted to ascertain the reliability of the scale and seek to operationalize its underlying components. The results indicate that the ISI is a reliable self-assessment scale for young people in a Swedish context. Furthermore, two components were distinguished by using principal component analysis. The components were operationalized into typical and atypical insomnia symptoms for teenagers, respectively. The typical symptoms were difficulties falling asleep combined with daytime complaints, while atypical symptoms consisted of difficulties falling asleep after waking up during the night, and difficulties with premature awakenings early in the mornings. The conclusion is that a Swedish translation of the ISI has good psychometric properties in teenagers, and that the underlying structure of the ISI for teenagers differs from what studies on adults have found, and to some extent studies on foreign teenagers. This could reflect age-related differences in sleep, cultural differences or problematic phrasing of the Swedish version of the ISI.