title: Clinical relevance of comorbidity in anxiety disorders: a report from the Netherlands Study of Depression and Anxiety (NESDA).
abstract: BACKGROUND
  To study the clinical relevance of type of comorbidity and number of comorbid disorders in anxiety disorders. Four groups were compared according to sociodemographic-, vulnerability- and clinical factors: single anxiety disorder, anxiety-anxiety comorbidity, anxiety-depressive comorbidity and "double" comorbidity (i.e. anxiety and depressive comorbidity).
  
  
  METHODS
  Data were obtained from the Netherlands Study of Anxiety and Depression (NESDA). A sample of 1004 participants with a current anxiety disorder was evaluated.
  
  
  RESULTS
  As compared with single anxiety, anxiety-anxiety comorbidity was associated with higher severity, greater chronicity and more treatment. Anxiety-anxiety comorbidity was associated with an earlier age of onset and a more chronic course compared with anxiety-depressive comorbidity, while anxiety-depressive comorbidity was associated with more severe symptoms and more impaired functioning than anxiety-anxiety comorbidity. "Double" comorbidity was associated with higher severity, greater chronicity, more treatment and increased disability. Sociodemographic and vulnerability factors were comparable among the four groups. Limitations A prospective design would be more appropriate to study the outcome. In this study no distinction was made between whether depression or anxiety disorder preceded the current anxiety disorder.
  
  
  CONCLUSIONS
  It is clinical relevant to diagnose and treat comorbidity among anxiety disorders as it is associated with higher severity and more chronicity. Whereas anxiety-anxiety comorbidity has an earlier age of onset and a more chronic course, anxiety-depressive comorbidity leads to more treatment and impaired functioning. "Double" comorbidity leads to even more severity, chronicity and impairment functioning compared with both anxiety-anxiety and anxiety-depressive comorbidity.
authors.affiliation: Department of Psychiatry and EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands. m.klein2@ggzcentraal.nl
authors.forename: Mieke Klein
authors.initials: MK
authors.lastname: Hofmeijer-Sevink
authors.forename: Neeltje M
authors.initials: NM
authors.lastname: Batelaan
authors.forename: Harold J G M
authors.initials: HJ
authors.lastname: van Megen
authors.forename: Brenda W
authors.initials: BW
authors.lastname: Penninx
authors.forename: Danielle C
authors.initials: DC
authors.lastname: Cath
authors.forename: Marcel A
authors.initials: MA
authors.lastname: van den Hout
authors.forename: Anton J L M
authors.initials: AJ
authors.lastname: van Balkom
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001008:Anxiety Disorders / Q000453:epidemiology* / Q000523:psychology; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D055815:Young Adult