Abstract
This study investigated the psychometric properties of the Insomnia Severity Index (ISI) in substance-using Ethiopian adults. A simple random sampling of houses and a purposive sampling selection was performed in Mizan city, Ethiopia (n = 406). Participants completed the ISI and a meta-cognition questionnaire and sociodemographic information. IBM SPSS software with Amos was used for data analysis. There was no major ceiling or floor effect in the ISI scores. The internal consistency (Cronbach's alpha = 0.68 and 0.78) and internal homogeneity (moderate to strong item-total ISI score correlations; r ≥ 0.47) were adequate. All of the ISI (item as well as total) scores correlated with the meta-cognition total scores (r = 0.16-0.44; p < .01). The exploratory factor analysis results were heterogeneous. However, the confirmatory factor analysis favored a 2-factor model. The ISI has good psychometric validity among Ethiopian adults with substance use.