title: Does a history of depression actually mediate smoking-related pain? Findings from a cross-sectional general population-based study.
abstract: BACKGROUND
  Smokers report more pain and worse functioning. The evidence from pain clinics suggests that depression affects this relationship: The association between smoking and chronic pain is weakened when controlling for depression. This study explored the relationship between smoking, pain and depression in a large general population-based cohort (Generation Scotland: Scottish Family Health Study).
  
  
  METHODS
  Chronic pain measures (intensity, disability), self-reported smoking status and a history of major depressive disorder (MDD) were analysed. A multivariate analysis of covariance determined whether smoking status was associated with both pain measures and a history of depressive illness. Using a statistical mediation model any mediating effect of depression on the relationship between smoking and chronic pain was sought.
  
  
  RESULTS
  Of all 24,024 participants, 30% (n = 7162) reported any chronic pain. Within this chronic pain group, 16% (n = 1158) had a history of MDD; 7108 had valid smoking data: 20% (n = 1408) were current smokers, 33% (n = 2351) former and 47% (n = 3349) never smokers. Current smokers demonstrated higher pain intensity and pain-related disability scores compared with former and non-smokers (p < 0.001 for all analyses). From the mediation model, the effect on pain intensity decreased (p < 0.001), indicating that the relationship between smoking and a history of depression contributes significantly to the effect of smoking on pain intensity. When applied to smoking-related pain disability, there was no mediation effect.
  
  
  CONCLUSIONS
  In contrast to smokers treated in pain clinics, a history of MDD mediated the relationship between smoking and pain intensity, but not pain-related disability in smokers in the community.
authors.affiliation: Medical Research Institute, University of Dundee, UK.
authors.forename: O
authors.initials: O
authors.lastname: van Hecke
authors.forename: N
authors.initials: N
authors.lastname: Torrance
authors.forename: L
authors.initials: L
authors.lastname: Cochrane
authors.forename: J
authors.initials: J
authors.lastname: Cavanagh
authors.forename: P T
authors.initials: PT
authors.lastname: Donnan
authors.forename: S
authors.initials: S
authors.lastname: Padmanabhan
authors.forename: D J
authors.initials: DJ
authors.lastname: Porteous
authors.forename: L
authors.initials: L
authors.lastname: Hocking
authors.forename: B H
authors.initials: BH
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059350:Chronic Pain / Q000453:epidemiology*; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000453:epidemiology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D012606:Scotland / Q000453:epidemiology; D012907:Smoking / Q000453:epidemiology*; D055815:Young Adult