Impact of Event Scale-6 (IES-6) for U.S. adults who experienced the COVID-19 pandemic

Background: COVID-19 pandemic causes psychological problems such as stress. It is important to accurately identify the level of stress and establish effective intervention. The Impact of Event Scale-6 (IES-6) is widely used for post-traumatic stress disorder (PTSD) screening by measuring the level of subjective stress, but there has been no research on its psychometric properties with individuals who experienced the COVID-19 pandemic. Methods: A random sample of 600 participants were randomly selected from a COVID-19 survey database (n = 6391). Rasch analysis was conducted to examine item fit, rating scale structure, construct validity, differential item functioning (DIF), and precision of the IES-6. Results: The principal component analysis of Rasch residuals (54.1% of the raw variance explained) and the average of residual correlations (average r =.19) supported the unidimensionality structure in the IES-6. The rating scale was suitable, and the item difficulty hierarchy was logical. The item fit and the DIF contrast were acceptable, except for item 5. The IES-6’s person reliability was.76, which was also an acceptable level. Conclusions: This study showed that the IES-6 has acceptable item-level psychometrics for screening the stress level in adults in the United States for individuals who have experienced the COVID-19 pandemic. The findings suggested that the IES-6 would be useful for the rapid identification of the high-level stressand allow clinicians to quickly provide interventions for people with the COVID-19 related stress and their families.