title: Factor analysis of the Hamilton Depression Rating Scale in Parkinson's disease.
abstract: BACKGROUND
  Several studies have validated the Hamilton Depression Rating Scale (HAMD) in patients with Parkinson's disease (PD), and reported adequate reliability and construct validity. However, the factorial validity of the HAMD has not yet been investigated. The aim of our analysis was to explore the factor structure of the HAMD in a large sample of PD patients.
  
  
  METHODS
  A principal component analysis of the 17-item HAMD was performed on data of 341 PD patients, available from a previous cross sectional study on anxiety. An eigenvalue ≥1 was used to determine the number of factors. Factor loadings ≥0.4 in combination with oblique rotations were used to identify which variables made up the factors. Kaiser-Meyer-Olkin measure (KMO), Cronbach's alpha, Bartlett's test, communality, percentage of non-redundant residuals and the component correlation matrix were computed to assess factor validity.
  
  
  RESULTS
  KMO verified the sample's adequacy for factor analysis and Cronbach's alpha indicated a good internal consistency of the total scale. Six factors had eigenvalues ≥1 and together explained 59.19% of the variance. The number of items per factor varied from 1 to 6. Inter-item correlations within each component were low. There was a high percentage of non-redundant residuals and low communality.
  
  
  CONCLUSIONS
  This analysis demonstrates that the factorial validity of the HAMD in PD is unsatisfactory. This implies that the scale is not appropriate for studying specific symptom domains of depression based on factorial structure in a PD population.
authors.affiliation: Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands. Electronic address: martijn.broen@mumc.nl.
authors.forename: M P G
authors.initials: MP
authors.lastname: Broen
authors.affiliation: Department of Psychiatry, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: A J H
authors.initials: AJ
authors.lastname: Moonen
authors.affiliation: Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: M L
authors.initials: ML
authors.lastname: Kuijf
authors.affiliation: Neurology and Movement Disorders Unit, Lille University Medical Center, Lille, France.
authors.forename: K
authors.initials: K
authors.lastname: Dujardin
authors.affiliation: Departments of Psychiatry and Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: L
authors.initials: L
authors.lastname: Marsh
authors.affiliation: Departments of Neurology and Department of Psychiatry, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: I H
authors.initials: IH
authors.lastname: Richard
authors.affiliation: School of Psychiatry, University of Western Australia and Fremantle Hospital, Fremantle, Western Australia, Australia.
authors.forename: S E
authors.initials: SE
authors.lastname: Starkstein
authors.affiliation: Area of Applied Epidemiology, National Centre for Epidemiology, and CIBERNED, Carlos III Institute of Health, Madrid, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Martinez-Martin
authors.affiliation: Department of Psychiatry, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: A F G
authors.initials: AF
authors.lastname: Leentjens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology*; D025341:Principal Component Analysis / Q000379:methods / Q000592:standards*; D011569:Psychiatric Status Rating Scales / Q000592:standards*
keywords: Depression; Factor analysis; Hamilton Depression Rating Scale; Parkinson's disease