Factor analysis of the hospital anxiety and depression scale among a Huntington's disease population

Introduction: Depression and anxiety are common in Huntington's disease, a genetic neurodegenerative disorder. There is a need for measurement tools of mood to be validated within a Huntington's disease population. The current study aimed to analyze the factor structure of the Hospital Anxiety and Depression Scale in Huntington's disease. Methods: Data from the European Huntington's Disease Network study REGISTRY 3 were used to undertake a factor analysis of the scale among a sample of 492 Huntington's disease mutation carriers. The sample was randomly divided into two equal subsamples and an exploratory factor analysis conducted on the first subsample suggested a two-factor interpretation, using eight of the items. A confirmatory factor analysis was then performed to test six possible models for goodness of fit. Results: A bifactor model, with all items loading onto a general distress factor, with two group factors, comprising four depression and four anxiety items, provided the best fit of the data. The salience of loadings on the bifactor model suggested that loadings were high on the general factor (accounting for 64% of the variance) and low on the group factors (21% for anxiety and 15% for depression). Conclusions: The findings suggest that eight items from the scale perform well among the sample. Consistent with recent developments in modeling the Hospital Anxiety and Depression Scale, a bifactor interpretation for an eight-item version outperformed other extant models. Our findings provide support for an eight-item version of the scale to be used as a measure of general distress within Huntington's disease populations.