Assessment of the structure of the Hospital Anxiety and Depression Scale in musculoskeletal patients

BACKGROUND: Research suggests there is a high prevalence of anxiety and depression amongst patients with chronic musculoskeletal pain, which can influence the effectiveness of rehabilitation programs. It is therefore important for clinicians involved in musculoskeletal rehabilitation programs to consider screening patients for elevated levels of anxiety and depression and to provide appropriate counselling or treatment where necessary. The HADS has been used as a screening tool for assessment of anxiety and depression in a wide variety of clinical groups. Recent research however has questioned its suitability for use with some patient groups due to problems with dimensionality and the behaviour of individual items. The aim of this study is to assess the underlying structure and psychometric properties of the HADS among patients attending musculoskeletal rehabilitation. METHODS: Data was obtained from 296 patients attending an outpatient musculoskeletal pain clinic. The total sample was used to identify the proportion of patients with elevated levels of anxiety and depression. Half the sample (n = 142) was used for exploratory factor analysis (EFA), with the holdout sample (n = 154) used for confirmatory factor analysis (CFA) to explore the underlying structure of the scale. RESULTS: A substantial proportion of patients were classified as probable cases on the HADS Anxiety subscale (38.2%) and HADS Depression subscale (30.1%), with the sample recording higher mean HADS subscales scores than many other patient groups (breast cancer, end-stage renal disease, heart disease) reported in the literature. EFA supported a two factor structure (representing anxiety and depression) as proposed by the scale's authors, however item 7 (an anxiety item) failed to load appropriately. Removing Item 7 resulted in a clear two factor solution in both EFA and CFA. CONCLUSION: The high levels of anxiety and depression detected in this sample suggests that screening for psychological comorbidity is important in musculoskeletal rehabilitation settings. It is necessary for clinicians who are considering using the HADS as a screening tool to first assess its suitability with their particular patient group. Although EFA and CFA supported the presence of two subscales representing anxiety and depression, the results with this musculoskeletal sample suggest that item 7 should be removed from the anxiety subscale.