title: Chronic low back pain and the risk of depression or anxiety symptoms: insights from a longitudinal twin study.
abstract: Pain is commonly associated with symptoms of depression or anxiety, although this relationship is considered bidirectional. There is limited knowledge regarding causal relationships.
  
  
  
  This study aims to investigate whether chronic low back pain (LBP) increases the risk of depression or anxiety symptoms, after adjusting for shared familial factors.
  
  
  
  This is a longitudinal, genetically informative study design from the Murcia Twin Registry in Spain.
  
  
  
  The patient sample included 1,269 adult twins with a mean age of 53 years.
  
  
  
  The outcome of depression or anxiety symptoms was evaluated with EuroQol questionnaire.
  
  
  
  Using logistic regression analyses, twins were initially assessed as individuals in the total sample analysis, followed by a co-twin case-control, which was partially (dizygotic [DZ] twins) and fully (monozygotic [MZ] twins) adjusted for shared familial factors. There was no external funding for this study and no conflict of interest was declared.
  
  
  
  There was a significant association between chronic LBP and the risk of depression or anxiety symptoms in the unadjusted total sample analysis (odds ratio [OR]: 1.81, 95% confidence interval [CI]: 1.34-2.44). After adjusting for confounders, the association remained significant (OR: 1.43, 95% CI: 1.05-1.95), although the adjusted co-twin case-control was non-significant in DZ (OR: 1.03, 95% CI: 0.50-2.13) and MZ twins (OR: 1.86, 95% CI: 0.63-5.51).
  
  
  
  The relationship between chronic LBP and the future development of depression or anxiety symptoms is not causal. The relationship is likely to be explained by confounding from shared familial factors, given the non-statistically significant associations in the co-twin case-control analyses.
authors.affiliation: Faculty of Health Sciences, The University of Sydney, 75 East St, Lidcombe, Sydney, NSW 2141, Australia. Electronic address: mfer4234@uni.sydney.edu.au.
authors.forename: Matt
authors.initials: M
authors.lastname: Fernandez
authors.affiliation: Murcia Twin Registry, Department of Human Anatomy and Psychobiology, University of Murcia and IMIB-Arrixaca, 30100 Murcia, Spain; Quantitative Genetics Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Brisbane, QLD 4006, Australia.
authors.forename: Lucia
authors.initials: L
authors.lastname: Colodro-Conde
authors.affiliation: Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55 DK-5230 Odense M, Denmark; Nordic Institute of Chiropractic and Clinical Biomechanics, University of Southern Denmark, Campusvej 55 DK-5230 Odense M, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Hartvigsen
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney, Level 5, 1 King St, Newtown, Sydney, NSW 2042, Australia; Institute of Bone and Joint Research, The Kolling Institute, Sydney Medical School, The University of Sydney, Royal North Shore Hospital, St Leonards, NSW 2065, Australia.
authors.forename: Manuela L
authors.initials: ML
authors.lastname: Ferreira
authors.affiliation: Faculty of Health Sciences, The University of Sydney, 75 East St, Lidcombe, Sydney, NSW 2141, Australia.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Refshauge
authors.affiliation: Faculty of Health Sciences, The University of Sydney, 75 East St, Lidcombe, Sydney, NSW 2141, Australia.
authors.forename: Marina B
authors.initials: MB
authors.lastname: Pinheiro
authors.affiliation: Murcia Twin Registry, Department of Human Anatomy and Psychobiology, University of Murcia and IMIB-Arrixaca, 30100 Murcia, Spain.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Ordoñana
authors.affiliation: Faculty of Health Sciences, The University of Sydney, 75 East St, Lidcombe, Sydney, NSW 2141, Australia.
authors.forename: Paulo H
authors.initials: PH
authors.lastname: Ferreira
mesh_terms: D000328:Adult; D003863:Depression / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000150:complications / Q000453:epidemiology* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
keywords: Anxiety; Chronic low back pain; Depression; Epidemiology; Genetics; Twins