An item response theory analysis of the Dissociative Experiences Scale II: examining psychometric properties and longitudinal stability among Japanese adults

In the present study, we applied item response theory (IRT) to the DES-II, which has traditionally been interpreted using classical test theory (CTT). Results suggested the need for item-focused assessment rather than relying solely on mean scores or cut-off points. Specifically, results suggested that the severity levels differed across item ratings, and to set cut-off points for each item based on the severity of the ratings. Furthermore, the possibility of cultural differences in response patterns of the DES-II was indicated. However, few studies have discussed cultural differences based on IRT; hence, further research should examine response patterns of the DES-II across various cultures. In conclusion, the DES-II is a valuable tool for assessing dissociative symptoms, with adequate psychometric properties from an item response theory perspective. Clinicians should consider item-specific responses in their assessments, and further research is needed to explore the scale's applicability across diverse populations.