title: The Relationship between Depression and Asthma: A Meta-Analysis of Prospective Studies.
abstract: BACKGROUND
  Previous studies have suggested that asthmatic patients often have comorbid depression; however, temporal associations remain unclear.
  
  
  OBJECTIVE
  To determine whether depression predicts asthma and, conversely, whether asthma predicts depression.
  
  
  METHODS
  A literature search was conducted without language restrictions using Pubmed, Embase, Cochrane and PsycINFO for studies published before January, 2015. Papers referenced by the obtained articles were also reviewed. Only comparative prospective studies with reported risk estimates of the association between depression and asthma were included. In order to investigate whether one of these conditions was predictive of the other, studies were excluded if enrolled participants had pre-existing depression or asthma. A random-effects model was used to calculate the pooled risk estimates for two outcomes: depression predicting asthma and asthma predicting depression.
  
  
  RESULTS
  Seven citations, derived from 8 cohort studies, met our inclusion criteria. Of these, six studies reported that depression predicted incident adult-onset asthma, including 83684 participants and 2334 incident cases followed for 8 to 20 years. Conversely, two studies reported that asthma predicted incident depression. These studies involved 25566 participants and 2655 incident cases followed for 10 and 20 years, respectively. The pooled adjusted relative risks (RRs) of acquiring asthma associated with baseline depression was 1.43 (95% CI, 1.28-1.61) (P<0.001). The adjusted RRs for acquiring depression associated with baseline asthma was 1.23 (95% CI, 0.72-2.10) (P = 0.45).
  
  
  CONCLUSIONS
  Depression was associated with a 43% increased risk of developing adult-onset asthma. However, asthma did not increase the risk of depression based on limited studies. Further prospective studies ascertaining the true association between asthma and subsequent risk of depression are warranted.
authors.affiliation: Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
authors.forename: Yong-Hua
authors.initials: YH
authors.lastname: Gao
authors.affiliation: Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
authors.forename: Hua-Si
authors.initials: HS
authors.lastname: Zhao
authors.affiliation: Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
authors.forename: Fu-Rui
authors.initials: FR
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Medical Sciences Graduate Program, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Pamela
authors.initials: P
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China.
authors.forename: Rong-Chang
authors.initials: RC
authors.lastname: Chen
authors.affiliation: Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
authors.forename: Guo-Jun
authors.initials: GJ
authors.lastname: Zhang
mesh_terms: D001249:Asthma / Q000150:complications / Q000453:epidemiology*; D003863:Depression / Q000150:complications / Q000453:epidemiology*; D003866:Depressive Disorder / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D011446:Prospective Studies; D012306:Risk