title: Bidirectional associations between clinically relevant depression or anxiety and COPD: a systematic review and meta-analysis.
abstract: BACKGROUND
  The longitudinal associations between depression or anxiety and COPD, and their comorbid effect on prognosis, have not been adequately addressed by previous reviews. We aimed to systematically assess these associations to inform guidelines and practice.
  
  
  METHODS
  We searched electronic databases for articles published before May 2012. Longitudinal studies in adult populations that reported an association between clinically relevant depression or anxiety and COPD, or that reported their comorbid effect on exacerbation and/or mortality, were eligible. Risk ratios (RRs) were pooled across studies using random-effects models and were verified using fixed-effects models. Heterogeneity was explored with subgroup and metaregression analyses.
  
  
  RESULTS
  Twenty-two citations yielded 16 studies on depression or anxiety as predictors of COPD outcomes (incident COPD/chronic lung disease or exacerbation) and/or mortality, in 28,759 participants followed for 1 to 8 years, and six studies on COPD as a predictor of depression in 7,439,159 participants followed for 1 to 35 years. Depression or anxiety consistently increased the risk of COPD outcomes (RR, 1.43; 95% CI, 1.22-1.68), particularly in higher-quality studies and in people aged ≤ 66 years. Comorbid depression increased the risk of mortality (RR, 1.83; 95% CI, 1.00-3.36), particularly in men. Anxiety (or psychologic distress) increased the risk of COPD outcomes/mortality in most studies (RR, 1.27; 95% CI, 1.02-1.58). Finally, COPD consistently increased the risk of depression (RR, 1.69; 95% CI, 1.45-1.96).
  
  
  CONCLUSIONS
  Depression and anxiety adversely affect prognosis in COPD, conferring an increased risk of exacerbation and possibly death. Conversely, COPD increases the risk of developing depression. These bidirectional associations suggest potential usefulness of screening for these disease combinations to direct timely therapeutic intervention.
authors: School of Nursing and Midwifery, Campbelltown Campus, NSW, Australia. Electronic address: e.atlantis@uws.edu.au.
authors: Evan
authors: E
authors: Atlantis
authors: School of Science and Health, University of Western Sydney, Campbelltown Campus, NSW, Australia.
authors: Paul
authors: P
authors: Fahey
authors: School of Nursing and Midwifery, Campbelltown Campus, NSW, Australia; School of Medicine, University of Western Sydney, Campbelltown Campus, NSW, Australia; Campbelltown Hospital, Department of Medicine, SLHD/SWSLHD, Campbelltown, NSW, Australia.
authors: Belinda
authors: B
authors: Cochrane
authors: School of Nursing and Midwifery, Campbelltown Campus, NSW, Australia; Centre for Pharmacology and Therapeutics, Division of Experimental Medicine, Imperial College, South Kensington, London, England.
authors: Sheree
authors: S
authors: Smith
mesh_terms: D001007:Anxiety / Q000453:epidemiology / Q000209:etiology*; D003863:Depression / Q000453:epidemiology / Q000209:etiology*; D014943:Global Health; D006801:Humans; D015994:Incidence; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications*; D018570:Risk Assessment