title: Hospital Anxiety and Depression (HAD) scale: factor structure, item analyses and internal consistency in a large population.
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.
  
  
  OBJECTIVE
  To examine the psychometric properties of the HAD scale in a large population.
  
  
  METHODS
  All inhabitants aged 20-89 years (n=92 100) were invited to take part in The Nord-Trøndelag 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 subscales were found to be internally consistent, with values of Cronbach's coefficient (alpha) 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.
authors.affiliation: Faculty of Psychology, University of Bergen, Bergen, Norway.
authors.forename: A
authors.initials: A
authors.lastname: Mykletun
authors.forename: E
authors.initials: E
authors.lastname: Stordal
authors.forename: A A
authors.initials: AA
authors.lastname: Dahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000175:diagnosis; D003866:Depressive Disorder / Q000175:diagnosis; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis*; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D015203:Reproducibility of Results