Dimensionality of the Chinese hospital anxiety depression scale in psychiatric outpatients: Mokken scale and factor analyses

Objective: The hospital anxiety and depression scale (HADS) is a widely used scale of anxiety and depression. However, recent studies have challenged the bi-dimensional scoring of the HADS. The present study was to examine the dimensionality of the Chinese HADS. Methods: We recruited a convenience sample of 214 adult psychiatric outpatients at a medical centre in Taiwan, and they completed the Chinese HADS. We used Mokken scale analysis (MSA), exploratory factor analysis (EFA), exploratory bifactor analysis (EBA) and confirmatory factor analysis (CFA) to examine the dimensionality of the Chinese HADS. Results: The Chinese HADS was a moderate Mokken scale (H_s= 0.44), and had a two-factor structure. EBA showed that one general factor, emotional distress, explained 68% of the common variance of the Chinese HADS. CFA confirmed that the bifactor model had the best fit statistics. The items 5 and 7 of the Chinese HADS contributed to structural ambiguity in the Chinese HADS subscales. Conclusions: The sum scores of the Chinese HADS were a reliable and valid unidimensional measure of emotional distress. The Chinese HADS subscales were incapable of differentiating between anxiety and depression. Clinicians and researchers should choose other scales that are specifically designed for measuring anxiety and depression.