Psychometric properties of insomnia severity index in Iranian adolescents

Sleep deprivation and insomnia have negative impacts on mental and physical health in adolescents. In order to examine the problems caused by insomnia, we need tools with acceptable validity and reliability for the target population. The aim of this study was to evaluate the psychometric properties of Insomnia Severity Index (ISI) in Iranian adolescent population.

The study was carried out as a descriptive-analytic normalization. Study group consisted of 701 adolescents aged 12 to 19, who were selected through cluster sampling. The participants completed ISI, Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Inventory (PSQI), Adolescent sleep hygiene scale (ASHS) and global sleep assessment questionnaire (GSAQ). In addition, SPSS ver.22 and AMOSS ver.10 were used to analyze the data.

The reliability of the test was obtained equal to 0.77 based on Cronbach's alpha and a good reliability (0.84) was obtained through test/retest method. Exploratory and confirmatory factor analyses with seven items were computed. The models fitness indexes were suitable for the structural model (CFI=0.99%, NFI=0.98%, GFI=0.99%, TLI=0.98%, RMSEA=0.049%). Moreover, there was a direct and significant correlation between the ISI index and the total score of other indexes. As to gender-based reliability, Cronbach's alpha was 0.78 in female adolescents and 0.85 in male adolescents.

The results indicated that the Persian version of the insomnia severity index can be used as a reliable and valid tool for assessing the severity of insomnia in Persian-speaking adolescents.