Development and validation of the DISCUS scale: a reliable short measure for assessing experienced discrimination in people with mental health problems on a global level

Background: The Discrimination and Stigma Scale (DISC-12) was specifically developed to measure experienced and anticipated discrimination reported by people with mental health problems. However, the length of the DISC-12 may represent a disadvantage especially in country settings with limited human capacity and infrastructure. The purpose of the study was to develop a short version of DISC-12 (DISCUS) to address these limitations. Methods: Data from 1087 participants with major depressive disorder and 732 patients with schizophrenia were collected as part of two research network studies across 35 countries - Anti Stigma Programme European Network (ASPEN) and International Study of Discrimination and Stigma (INDIGO). We used a Meta Exploratory Factor Analysis (meta-EFA) and a Multiple Causes Multiple Indicators (MIMIC) Model to reduce the number of items in the DISC-12 scale. The validity and reliability of the reduced scale (DISCUS) was tested in 202 people with the full spectrum of mental disorders recruited in a cross-sectional study conducted in South London. Psychometric validation for the reduced scale used confirmatory factor analysis and measures of Cronbach's alpha and Pearson's correlation coefficient. Results: meta-EFA reduced twenty-one items to twelve items. An additional item was discarded with the use of the MIMIC model. The 11-item DISCUS demonstrated excellent reliability (Cronbach's alpha >0.85), good fit (Tucker Lewis Index and Comparative Fit Index value>0.9) and weak to moderate construct validity. Conclusions: The DISCUS scale is a consistent and valid instrument to measure experienced and anticipated discrimination predominantly in personal and social relationships in global settings.