title: Validation of the German version of the insomnia severity index in adolescents, young adults and adult workers: results from three cross-sectional studies.
abstract: A variety of objective and subjective methods exist to assess insomnia. The Insomnia Severity Index (ISI) was developed to provide a brief self-report instrument useful to assess people's perception of sleep complaints. The ISI was developed in English, and has been translated into several languages including German. Surprisingly, the psychometric properties of the German version have not been evaluated, although the ISI is often used with German-speaking populations.
  
  
  
  The psychometric properties of the ISI are tested in three independent samples: 1475 adolescents, 862 university students, and 533 police and emergency response service officers. In all three studies, participants provide information about insomnia (ISI), sleep quality (Pittsburgh Sleep Quality Index), and psychological functioning (diverse instruments). Descriptive statistics, gender differences, homogeneity and internal consistency, convergent validity, and factorial validity (including measurement invariance across genders) are examined in each sample.
  
  
  
  The findings show that the German version of the ISI has generally acceptable psychometric properties and sufficient concurrent validity. Confirmatory factor analyses show that a 1-factor solution achieves good model fit. Furthermore, measurement invariance across gender is supported in all three samples.
  
  
  
  While the ISI has been widely used in German-speaking countries, this study is the first to provide empirical evidence that the German version of this instrument has good psychometric properties and satisfactory convergent and factorial validity across various age groups and both men and women. Thus, the German version of the ISI can be recommended as a brief screening measure in German-speaking populations.
authors.affiliation: Department of Sport, Exercise and Health, University of Basel, St. Jakobsturm, Birsstrasse 320B, 4052, Basel, Switzerland. markus.gerber@unibas.ch.
authors.forename: Markus
authors.initials: M
authors.lastname: Gerber
authors.affiliation: Department of Sport, Exercise and Health, University of Basel, St. Jakobsturm, Birsstrasse 320B, 4052, Basel, Switzerland.
authors.forename: Christin
authors.initials: C
authors.lastname: Lang
authors.affiliation: Department of Psychology, University of Warwick, Coventry, UK.
authors.forename: Sakari
authors.initials: S
authors.lastname: Lemola
authors.affiliation: Department of Sport, Exercise and Health, University of Basel, St. Jakobsturm, Birsstrasse 320B, 4052, Basel, Switzerland.
authors.forename: Flora
authors.initials: F
authors.lastname: Colledge
authors.affiliation: Center for Affective, Stress and Sleep Disorders, Psychiatric Clinics of the University of Basel, Basel, Switzerland.
authors.forename: Nadeem
authors.initials: N
authors.lastname: Kalak
authors.affiliation: Center for Affective, Stress and Sleep Disorders, Psychiatric Clinics of the University of Basel, Basel, Switzerland.
authors.forename: Edith
authors.initials: E
authors.lastname: Holsboer-Trachsler
authors.affiliation: Department of Sport, Exercise and Health, University of Basel, St. Jakobsturm, Birsstrasse 320B, 4052, Basel, Switzerland.
authors.forename: Uwe
authors.initials: U
authors.lastname: Pühse
authors.affiliation: Department of Sport, Exercise and Health, University of Basel, St. Jakobsturm, Birsstrasse 320B, 4052, Basel, Switzerland.|Center for Affective, Stress and Sleep Disorders, Psychiatric Clinics of the University of Basel, Basel, Switzerland.
authors.forename: Serge
authors.initials: S
authors.lastname: Brand
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D011594:Psychometrics / Q000379:methods; D015203:Reproducibility of Results; D057566:Self Report; D012720:Severity of Illness Index; D012890:Sleep; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis* / Q000523:psychology*; D011795:Surveys and Questionnaires / Q000592:standards*; D014175:Translating; D055815:Young Adult
keywords: German; Insomnia; Measurement invariance; Psychological functioning; Sleep; Validation