Development and Validation of a Short-form (6-item) Version of the Clinician-Administered Dissociative States Scale (CADSS-SF)

Background: State dissociation is commonly assessed using the Clinician Administered Dissociative States Scale (CADSS; 19-items). A briefer CADSS would have many advantages, enabling assessment of relatively transient dissociative states and allowing repeated assessment within short intervals while minimizing participant burden. This is especially relevant in studies of dissociative drugs which cause sedation and psychomotor slowing. Here we describe the process of developing a short-form version of the CADSS (CADSS-SF).Methods: In the ‘development phase’ using data from three experimental pharmacological studies on nitrous oxide (N2O) in healthy volunteers (n=229) we identified the most ‘N2O-responsive’ items with the highest item-total correlations, endorsed by experts and consistent with published accounts on the phenomenology of drug-induced dissociation. Initially identified items were subjected to confirmatory factor analysis using a separate validation dataset (n=80) which tested a series of one and two factor models with 6-8 items.Results: A 6-item, single-factor CADSS-SF showed excellent model fit (χ2(9)=0.246, p=0.246, CFI/TLI>0.99, RMSEA=0.059). The CADSS-SF was internally consistent (=0.87) and strongly correlated with the full scale (r≥0.88).Discussion: The CADSS-SF is a promising tool for rapid assessment of dissociation. It may be especially useful for capturing fleeting experimentally-induced dissociative phenomena that would otherwise be disrupted through the process of extended self-reporting, or for studying dissociation during drug intoxication, which is often accompanied by psychomotor slowing, sedation and inattention. The brevity of the scale may allow tracking of changes in dissociation over relatively brief periods. However, it may be less appropriate for capturing the multidimensionality of dissociative phenomena.