title: An examination of generalized anxiety disorder and dysthymic disorder by latent class analysis.
abstract: BACKGROUND
  The nosological status of generalized anxiety disorder (GAD) versus dysthymic disorder (DD) has been questioned. The aim of this study was to examine qualitative differences within (co-morbid) GAD and DD symptomatology.
  
  
  METHODS
  Latent class analysis was applied to anxious and depressive symptomatology of respondents from three population-based studies (2007 Australian National Survey of Mental Health and Wellbeing; National Comorbidity Survey Replication; and Netherlands Mental Health Survey and Incidence Study-2; together known as the Triple study) and respondents from a multi-site naturalistic cohort [Netherlands Study of Depression and Anxiety (NESDA)]. Sociodemographics and clinical characteristics of each class were examined.
  
  
  RESULTS
  A three-class (Triple study) and two-class (NESDA) model best fitted the data, reflecting mainly different levels of severity of symptoms. In the Triple study, no division into a predominantly GAD or DD co-morbidity subtype emerged. Likewise, in spite of the presence of pure GAD and DD cases in the NESDA sample, latent class analysis did not identify specific anxiety or depressive profiles in the NESDA study. Next, sociodemographics and clinical characteristics of each class were examined. Classes only differed in levels of severity.
  
  
  CONCLUSIONS
  The absence of qualitative differences in anxious or depressive symptomatology in empirically derived classes questions the differentiation between GAD and DD.
authors.affiliation: Department of Psychiatry and the EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Rhebergen
authors.affiliation: Department of Psychiatry and the EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, The Netherlands.
authors.forename: I M
authors.initials: IM
authors.lastname: van der Steenstraten
authors.affiliation: Clinical Research Unit for Anxiety and Depression (CRUfAD), University of New South Wales, Sydney, NSW, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Sunderland
authors.affiliation: Netherlands Institute of Mental Health and Addiction, Utrecht, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: de Graaf
authors.affiliation: Netherlands Institute of Mental Health and Addiction, Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Ten Have
authors.affiliation: Genetic Epidemiological Research Branch, National Institute of Mental Health, Bethesda, MD, USA.
authors.forename: F
authors.initials: F
authors.lastname: Lamers
authors.affiliation: Department of Psychiatry and the EMGO Institute for Health and Care Research, VU University Medical Center Amsterdam, The Netherlands.
authors.forename: B W J H
authors.initials: BW
authors.lastname: Penninx
authors.affiliation: Clinical Research Unit for Anxiety and Depression (CRUfAD), University of New South Wales, Sydney, NSW, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Andrews
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001008:Anxiety Disorders / Q000145:classification* / Q000453:epidemiology; D001315:Australia / Q000453:epidemiology; D019263:Dysthymic Disorder / Q000145:classification* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D055815:Young Adult