Measuring stigma across neurological conditions: The development of the stigma scale for chronic illness (SSCI)

Purpose: Most measures of stigma are illness specific and do not allow for comparisons across conditions. As part of a study of health-related quality of life for people with neurological disorders, our team developed an instrument to assess the stigma for people with chronic illnesses. Methods: We based item content on literature review, responses from focus groups, and cognitive interviews. We then administered the items to people with neurological disorders for psychometric testing. Results: Five hundred eleven participants completed items of the stigma scale. Exploratory factor analysis produced two factors that were highly correlated (r = 0.81). Confirmatory factor analysis produced high standardized loadings on an overall stigma factor (0.68-0.94), with poorer loadings on the two sub-domains (-0.12 to 0.53). These results demonstrated a sufficiently unidimensional scale that corresponded with the bifactor model. Item response theory modeling suggested good model fit, and differential item functioning analyses indicated that the 24-item scale showed potential for measurement equivalence across conditions. Conclusions: Our efforts produced a stigma scale that had promising psychometric properties. Further study can provide additional information about the SSCI and its benefit in measuring the impact of stigma across conditions.