The Updated Italian Version of the Impact of Event Scale-Revised: A Bifactor Exploratory Structural Equation Modeling Perspective

The Impact Event Scale-Revised (IES-R) is awidely used instrument for assessing posttraumatic stress disorder. Our aimwas to further investigate the psychometric properties of the IES-R in a sample of 231 participants (56.3% females; Mage= 32.7, SD= 12.61). Confirmatory factor analysis and exploratory structural equation modeling models were tested and compared to select the most suitable factor representation for the data. Our findings showed that a bifactor exploratory structural equation modeling model was the most appealing factor solution, χ2(51)= 52.714, comparative fit index=.998, Tucker–Lewis index= .997, root-mean-square error of approximation=. 012, standardized root-mean-square residual=.020, Akaike Information Criterion= 8,478.705, Bayesian Information Criterion=8,767.868, adjusted Bayesian Information Criterion= 8,501.635, with a well-defined G-factor and three weak S-factors (avoidance, intrusion, and hyperarousal); internal reliability coefficients were excellent (ω= .952, ωs= .952, ωH= .919, .009,ωHS,.013). Our work supports the usefulness of the bifactor exploratory structural equation modeling framework and suggests that the IES-R is a robust and well-suited scale for assessing posttraumatic stress disorder in current research and clinical practice.