The Inclusion of the Other in the Self-Scale (IOSS) as a valid self-discrepancy measure after stroke.

Self-discrepancy, i.e., negative changes in self-concept, is a common post-stroke phenomenon which is closely associated with depression and quality of life. In earlier research, self-discrepancy has been measured with the 18-item seven-stepped Head Injury Semantic Differential Scale (HISDS-III), by comparing pre- and post-morbid self-concepts. As completing this scale may be demanding especially for cognitively impaired stroke survivors, a straightforward instrument is desirable. Therefore, the validity of the Inclusion of the Other in the Self Scale (IOSS), which measures self-discrepancy with a single visualized item, was cross-sectionally examined in 123 individuals three years after stroke. Results revealed a substantial correlation between the IOSS and the established HISDS-III (r = .47, p < .001) and a Gini Index corresponding to an AUC of 0.74, both indicating convergent validity. Both measures showed similar correlations with relevant covariates. Prediction of depressive symptoms using established predictors was significantly improved by the inclusion of the IOSS (ΔR² = .07, p < .001). The findings indicate the high validity of the IOSS as an economic measure of global self-discrepancy after stroke. In addition, the results confirm self-discrepancy as a relevant determinant of post-stroke depression and thus as a potential target for psychological interventions in stroke patients.