The structure of the Hospital Anxiety and Depression Scale: Theoretical and methodological considerations.

The Hospital Anxiety and Depression Scale (HADS; Zigmond - Snaith, 1983) is widely used; however, its factor structure is unclear, with studies reporting differing unidimensional, two-factor and three-factor models. We aimed to address some key theoretical and methodological issues contributing to inconsistencies in HADS structures across samples. We reviewed existing HADS models and compared their fit using confirmatory factor analysis (CFA). We also investigated methodological effects by comparing factor structures derived from Rasch and Principal Components Analysis (PCA) methods, as well as effects of a negative wording factor. An Australian community-dwelling sample consisting of 189 females and 158 males aged 17-86 (M = 35.73, SD = 17.41) completed the 14-item HADS. The Rasch Analysis, PCA and CFA all supported the original two-factor structure. Although some three-factor models had good fit, they had unacceptable reliability. In the CFA, a hierarchical bifactor model with a general distress factor and uncorrelated depression and anxiety subscales produced the best fit, but the general factor was not unidimensional. The addition of a negative wording factor improved model fit. These findings highlight the effects of differing methodologies in producing inconsistent HADS factor structures across studies. Further replication of model fit across samples and refinement of the HADS items is warranted.