title: Comorbidity between depression and asthma via immune-inflammatory pathways: a meta-analysis.
abstract: BACKGROUND
  Depression is often present in patients with asthma and vice versa. In this review, we aimed to summarize reports on the comorbidity of depression and asthma, and to seek evidence that the biological mechanisms of allergy may have an important role linking asthma and depression.
  
  
  METHODS
  To explore the relationship and pathway underpinning this comorbidity, we reviewed medical articles and undertook a meta-analysis of epidemiological studies on (i) incidence of asthma in patients with depression; (ii) morbidity of depression in patients with asthma; (iii) concentration of cytokines in depressed subjects.
  
  
  RESULTS
  High level of comorbidity of asthma and depression was consistently demonstrated in 10 studies of patients with asthma and four studies of patients with depression. In search of biological connection of the two illnesses, thirty-eight studies were included for Meta-analyses examining differences in allergy related cytokines between patients with depression and non-depressive subjects. In people with depression, concentration of monocytes related cytokines such as IL-1 (1.56ng/mL, 95% CI: 0.00-3.12, p=0.05) was significantly higher than that in non-depressive control subjects. At the same time, some other inflammatory factors including IL-4 (5.77pg/mL, 95% CI: 2.34-9.21, p=0.00010), IL-6 (1.44ng/mL, 95% CI: 1.05-1.82, p<0.00001) and TNF-α(3.01ng/mL, 95% CI: 1.76-4.26, p<0.00001) were extremely significantly higher in depressed people compared with the controls. There was no significant differences of the T cell related cytokine levels, IFN-γ (-0.16ng/mL, 95% CI: -0.85-7.73, p=0.97), accompanied with IL-10 (0.67ng/mL, 95% CI: -0.84-2.18, p=0.38) between depressive and non-depressive groups.
  
  
  CONCLUSIONS
  The varying levels of certain cytokines play an important role in arousing and remitting asthma and depression. That suggests inflammatory response could be a common pathway adjusting both depression and asthma.
authors.affiliation: Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China.
authors.forename: Mingdi
authors.initials: M
authors.lastname: Jiang
authors.affiliation: National Centre for Suicide Research and Prevention, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Ping
authors.initials: P
authors.lastname: Qin
authors.affiliation: Section of Environmental Biomedicine, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China. Electronic address: yangxu@mail.ccnu.edu.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Yang
mesh_terms: D001249:Asthma / Q000453:epidemiology* / Q000276:immunology; D015897:Comorbidity; D016207:Cytokines / Q000276:immunology*; D003866:Depressive Disorder / Q000453:epidemiology* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male
chemical_list: D016207:Cytokines
keywords: Allergy; Asthma; Cytokines; Depression