title: Mental-physical co-morbidity and its relationship with disability: results from the World Mental Health Surveys.
abstract: BACKGROUND
  The relationship between mental and physical disorders is well established, but there is less consensus as to the nature of their joint association with disability, in part because additive and interactive models of co-morbidity have not always been clearly differentiated in prior research.
  
  
  METHODS
  Eighteen general population surveys were carried out among adults as part of the World Mental Health (WMH) Survey Initiative (n=42 697). DSM-IV disorders were assessed using face-to-face interviews with the Composite International Diagnostic Interview (CIDI 3.0). Chronic physical conditions (arthritis, heart disease, respiratory disease, chronic back/neck pain, chronic headache, and diabetes) were ascertained using a standard checklist. Severe disability was defined as on or above the 90th percentile of the WMH version of the World Health Organization Disability Assessment Schedule (WHODAS-II).
  
  
  RESULTS
  The odds of severe disability among those with both mental disorder and each of the physical conditions (with the exception of heart disease) were significantly greater than the sum of the odds of the single conditions. The evidence for synergy was model dependent: it was observed in the additive interaction models but not in models assessing multiplicative interactions. Mental disorders were more likely to be associated with severe disability than were the chronic physical conditions.
  
  
  CONCLUSIONS
  This first cross-national study of the joint effect of mental and physical conditions on the probability of severe disability finds that co-morbidity exerts modest synergistic effects. Clinicians need to accord both mental and physical conditions equal priority, in order for co-morbidity to be adequately managed and disability reduced.
authors: Department of Psychological Medicine, Otago University, Wellington, New Zealand. kate.scott@otago.ac.nz
authors: K M
authors: KM
authors: Scott
authors: M
authors: M
authors: Von Korff
authors: J
authors: J
authors: Alonso
authors: M C
authors: MC
authors: Angermeyer
authors: E
authors: E
authors: Bromet
authors: J
authors: J
authors: Fayyad
authors: G
authors: G
authors: de Girolamo
authors: K
authors: K
authors: Demyttenaere
authors: I
authors: I
authors: Gasquet
authors: O
authors: O
authors: Gureje
authors: J M
authors: JM
authors: Haro
authors: Y
authors: Y
authors: He
authors: R C
authors: RC
authors: Kessler
authors: D
authors: D
authors: Levinson
authors: M E
authors: ME
authors: Medina Mora
authors: M
authors: M
authors: Oakley Browne
authors: J
authors: J
authors: Ormel
authors: J
authors: J
authors: Posada-Villa
authors: M
authors: M
authors: Watanabe
authors: D
authors: D
authors: Williams
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D002908:Chronic Disease / Q000453:epidemiology* / Q000523:psychology; D015897:Comorbidity; D003431:Cross-Cultural Comparison; D004185:Disability Evaluation; D006233:Persons with Disabilities / Q000523:psychology / Q000706:statistics & numerical data*; D014943:Global Health; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D007407:Interviews as Topic; D001523:Mental Disorders / Q000453:epidemiology*; D008603:Mental Health / Q000706:statistics & numerical data*; D008875:Middle Aged; D016017:Odds Ratio; D012720:Severity of Illness Index