Validation study of the Italian version of the Insomnia Severity Index (ISI)


To test the factorial structure of the Italian version of the Insomnia Severity Index (ISI) using a confirmatory approach and to assess its psychometric properties. ISI questionnaire was completed by 272 patients (average age 41.28, range 18–73) with insomnia diagnosis performed by a sleep medicine physician and retrospectively enrolled in the study. All patients underwent Cognitive Behavioral Treatment for Insomnia (CBT-I) and completed sleep diaries before starting the treatment. Data from sleep diaries were analyzed for assessing concurrent validity of the ISI. Confirmatory factor analysis (CFA) for ordinal Likert-type items was applied to compare four competing models proposed in the literature. 244 patients, out of the 272, completed the ISI at the end of CBT-I. A comparison of ISI score before and after treatment was performed. The CFA analysis confirmed the presence of three main factors conceptualized as severity and impact of the disease along with sleep satisfaction. Significant correlations of the first three items of the questionnaire, investigating three different subtypes of insomnia, and the subjective measures from the sleep diaries were found, thus supporting the concurrent validity of the test. Sleep efficiency (SE) had a significant inverse correlation with the severity and satisfaction factors and with ISI’s total score. After CBT-I treatment, a significant reduction of ISI’s scores was observed, thus confirming the effectiveness of the CBT-I treatment. The internal reliability coefficient was 0.75. The ISI questionnaire maintains good psychometric properties in the Italian version, thus confirming that this instrument is reliable for detecting insomnia severity and identifying patients’ symptoms.

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  1. 1.

    Ohayon MM (2002) Epidemiology of insomnia: what we know and what we still need to learn. Sleep Med Rev 6:97–111

    Article  PubMed  Google Scholar 

  2. 2.

    Riemann D, Voderholzer U (2003) Primary insomnia: a risk factor to develop depression? J Affect Disord 76:255–259

    Article  PubMed  Google Scholar 

  3. 3.

    American Academy of Sleep Medicine (2014) International classification of sleep disorders, 3rd edn. American Academy of Sleep Medicine, Darien

    Google Scholar 

  4. 4.

    American Psychiatric Association (2013) Diagnostic and statistical manual of mental disorders, 5th edn. American Psychiatric Publishing, Arlington

    Google Scholar 

  5. 5.

    Riemann D, Nissen C, Palagini L, Otte A, Perlis M, Spiegelhalder K (2015) The neurobiology, investigation, and treatment of chronic insomnia. Lancet Neurol 14:547–558

    Article  PubMed  Google Scholar 

  6. 6.

    Bastien HC, Vallières A, Morin CM (2001) Validation of the Insomnia Severity Index as an outcome measure for insomnia research. Sleep Med 2:297–307

    Article  PubMed  Google Scholar 

  7. 7.

    Yu DS (2010) Insomnia Severity Index: psychometric properties with Chinese community-dwelling older people. J Adv Nurs 66:2350–2359

    Article  PubMed  Google Scholar 

  8. 8.

    Lahan V, Gupta R (2011) Translation and validation of the insomnia severity index in hindi language. Indian J Psychol Med 33:172–176

    Article  PubMed  PubMed Central  Google Scholar 

  9. 9.

    Suleiman KH, Yates BC (2011) Translating the insomnia severity index into Arabic. J Nurs Scholarsh 43:49–53

    Article  PubMed  Google Scholar 

  10. 10.

    Yazdi Z, Sadeghniiat-Haghighi K, Zohal MA, Elmizadeh K (2012) Validity and reliability of the Iranian version of the Insomnia Severity Index. Malays J Med Sci 19:31–36

    PubMed  PubMed Central  Google Scholar 

  11. 11.

    Fernandez-Mendoza J, Rodriguez-Muñoz A, Vela-Bueno A, Olavarrieta-Bernardino S, Calhoun SL, Bixler EO, Vgontzas AN (2012) The Spanish version of the Insomnia Severity Index: a confirmatory factor analysis. Sleep Med 13:207–210

    Article  PubMed  Google Scholar 

  12. 12.

    Cho YW, Song ML, Morin CM (2014) Validation of a Korean version of the insomnia severity index. J Clin Neurol 10:210–215

    Article  PubMed Central  Google Scholar 

  13. 13.

    Sadeghniiat-Haghighi K, Montazeri A, Khajeh-Mehrizi A, Nedjat S, Aminian O (2014) The Insomnia Severity Index: cross-cultural adaptation and psychometric evaluation of a Persian version. Qual Life Res 23:533–537

    Article  PubMed  Google Scholar 

  14. 14.

    Morin CM, Belleville G, Bélanger L, Ivers H (2011) The insomnia severity index: psychometric indicators to detect insomnia cases and evaluate treatment response. Sleep 34:601–608

    PubMed  PubMed Central  Google Scholar 

  15. 15.

    Rosseel Y (2012) lavaan: an R Package for structural equation modeling. J Stat Softw 48:1–36

    Article  Google Scholar 

  16. 16.

    Revelle W (2015) psych: procedures for personality and psychological research, Northwestern University, Evanston, Illinois, USA, Version = 1.5.8. Retrieved 30 Aug 2015

  17. 17.

    Savard MH, Savard J, Simard S, Ivers H (2005) Empirical validation of the Insomnia Severity Index in cancer patients. Psychooncology 14:429–441

    Article  PubMed  Google Scholar 

  18. 18.

    Chung KF, Kan KKK, Yeung WF (2011) Assessing insomnia in adolescents: comparison of insomnia severity index, Athens insomnia scale and sleep quality index. Sleep Med 12:463–470

    Article  PubMed  Google Scholar 

  19. 19.

    Jöreskog KG (2005) Structural equation modeling with ordinal variables using LISREL. Technical report, Scientific Software International, Inc., Lincolnwood, IL, 2005. Retrieved 10 Mar 2016

  20. 20.

    Di-Stefano C (2002) The impact of categorization with confirmatory factor analysis. Struct Equ Model 9:327–346

    Article  Google Scholar 

  21. 21.

    Holgado FP, Chacón S, Barbero I, Vila E (2010) Polychoric versus Pearson correlations in exploratory and confirmatory factor analysis of ordinal variables. Qual Quant 44:153–166

    Article  Google Scholar 

  22. 22.

    Forero CG, Maydeu-Olivares A, Gallardo-Pujol D (2009) Factor analysis with ordinal indicators: a Monte Carlo study comparing DWLS and ULS estimation. Struct Equ Model 16:625–641

    Article  Google Scholar 

  23. 23.

    Hu LT, Bentler PM (1999) Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Model 6:1–55

    Article  Google Scholar 

  24. 24.

    Miles J, Shevlin M (1998) Effects of sample size, model specification and factor loadings on the GFI in confirmatory factor analysis. Personal Individ Differ 25:85–90

    Article  Google Scholar 

  25. 25.

    Hooper D, Coughlan J, Mullen M (2008) Structural equation modelling: guidelines for determining model fit. EJBRM 6:53–60

    Google Scholar 

  26. 26.

    Beaujean AA (2014) Latent variable modeling using R: A step by step guide. Routledge/Taylor and Francis, New York

    Google Scholar 

  27. 27.

    Bentler PM (1990) Comparative fit indexes in structural models. Psychol Bull 107:238–246

    CAS  Article  PubMed  Google Scholar 

  28. 28.

    Zumbo BD, Gadermann AM, Zeisser C (2007) Ordinal versions of coefficients alpha and theta for Likert rating scales. J Mod Appl Stat Methods 6:21–29

    Google Scholar 

  29. 29.

    Gadermann AM, Guhn M, Zumbo BD (2012) Estimating ordinal reliability for Likert-type and ordinal item response data: a conceptual, empirical, and practical guide. PARE 17(3):1–13

  30. 30.

    Sierra JC, Guillén-Serrano V, Santos-Iglesias P (2008) Insomnia Severity Index: some indicators about its reliability and validity on an older adult sample. Rev Neurol 47:566–570

    CAS  PubMed  Google Scholar 

  31. 31.

    Carney CE, Harris AL, Moss TG, Edinger JD (2010) Distinguishing rumination from worry in clinical insomnia. Behav Res Ther 48:540–546

    Article  PubMed  PubMed Central  Google Scholar 

  32. 32.

    Riemann D, Spiegelhalder K, Feige B, Voderholzer U, Berger M, Perlis M, Nissen C (2010) The hyperarousal model of insomnia: a review of the concept and its evidence. Sleep Med Rev 14:19–31

    Article  PubMed  Google Scholar 

  33. 33.

    Bland JM, Altman DG (1997) Cronbach’s alpha. BMJ 314:572

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  34. 34.

    Natale V, Léger D, Bayon V, Erbacci A, Tonetti L, Fabbri M, Martoni M (2015) The consensus sleep diary: quantitative criteria for primary insomnia diagnosis. Psychosom Med 77:413–418

    Article  PubMed  Google Scholar 

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Correspondence to Luigi Ferini-Strambi.

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Castronovo, V., Galbiati, A., Marelli, S. et al. Validation study of the Italian version of the Insomnia Severity Index (ISI). Neurol Sci 37, 1517–1524 (2016).

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  • Insomnia Severity Index
  • Insomnia
  • Sleep diary
  • Confirmatory factor analysis
  • Cognitive behavioral therapy for insomnia