Hospital Anxiety and Depression (HAD) scale: Factor structure, item analyses and internal consistency in a large population

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Abstract
Background: The Hospital Anxiety and Depression (HAD) rating scale is a commonly used questionnaire. Former studies have given inconsistent results as to the psychometric properties of the HAD scale.Aims: To examine the psychometric properties of the HAD scale in a large population.Method: All inhabitants aged 20–89 years (n=92 100) were invited to take part in The Nord-Tr⊘ndelag Health Study, Norway. A total of 65 648 subjects participated, and only completed HAD scale forms (n=51 930) formed the basis for the psychometric examinations.Results: Principal component analysis extracted two factors in the HAD scale that accounted for 57% of the variance. The anxiety and depression sub-scales shared 30% of the variance. Both sub-scales were found to be internally consistent, with values of Cronbach's coefficient (a) being 0.80 and 0.76, respectively.Conclusions: Based on data from a large population, the basic psychometric properties of the HAD scale as a self-rating instrument should be considered as quite good in terms of factor structure, intercorrelation, homogeneity and internal consistency.