title: Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts.
abstract: BACKGROUND
  Previous studies have shown that gainfully employed individuals with high work demands and low control at work (denoted "job strain") are at increased risk of common mental disorders, including depression. Most existing studies have, however, measured depression using self-rated symptom scales that do not necessarily correspond to clinically diagnosed depression. In addition, a meta-analysis from 2008 indicated publication bias in the field.
  
  
  METHODS
  This study protocol describes the planned design and analyses of an individual participant data meta-analysis, to examine whether job strain is associated with an increased risk of clinically diagnosed unipolar depression based on hospital treatment registers.  The study will be based on data from approximately 120,000 individuals who participated in 14 studies on work environment and health in 4 European countries. The self-reported working conditions data will be merged with national registers on psychiatric hospital treatment, primarily hospital admissions. Study-specific risk estimates for the association between job strain and depression will be calculated using Cox regressions. The study-specific risk estimates will be pooled using random effects meta-analysis.
  
  
  CONCLUSIONS
  The planned analyses will help clarify whether job strain is associated with an increased risk of clinically diagnosed unipolar depression. As the analysis is based on pre-planned study protocols and an individual participant data meta-analysis, the pooled risk estimates will not be influenced by selective reporting and publication bias. However, the results of the planned study may only pertain to severe cases of unipolar depression, because of the outcome measure applied.
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, DK-2100, Denmark.
authors.forename: Ida E H
authors.initials: IE
authors.lastname: Madsen
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, DK-2100, Denmark.
authors.forename: Harald
authors.initials: H
authors.lastname: Hannerz
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Solja T
authors.initials: ST
authors.lastname: Nyberg
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, SE-171 77, Sweden.
authors.forename: Linda L
authors.initials: LL
authors.lastname: Magnusson Hanson
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Ahola
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, SE-171 77, Sweden ; Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, SE-104 22, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK ; Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, GB-EH8 9JZ, UK ; Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, GB-EH8 9JZ, UK.
authors.forename: G David
authors.initials: GD
authors.lastname: Batty
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, DK-2100, Denmark.
authors.forename: Jakob B
authors.initials: JB
authors.lastname: Bjorner
authors.affiliation: Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, DK-2400, Denmark.
authors.forename: Marianne
authors.initials: M
authors.lastname: Borritz
authors.affiliation: Federal Institute for Occupational Safety and Health (BAuA, Berlin, DE- 10317, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Burr
authors.affiliation: Department of Medical Sociology, University of Düsseldorf, Düsseldorf, DE-40225, Germany.
authors.forename: Nico
authors.initials: N
authors.lastname: Dragano
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK ; School of Community and Social Medicine, University of Bristol, Bristol, GB-BS8 2PS, UK.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Ferrie
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Hamer
authors.affiliation: Institute of Behavioral Sciences, University of Helsinki, Helsinki, FI-00014, Finland.
authors.forename: Markus
authors.initials: M
authors.lastname: Jokela
authors.affiliation: Department of Health Sciences, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Knutsson
authors.affiliation: Department of Public Health, University of Helsinki, Helsinki, FI-00014, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Koskinen
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, SE-171 77, Sweden.
authors.forename: Constanze
authors.initials: C
authors.lastname: Leineweber
authors.affiliation: Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, DK-2400, Denmark.
authors.forename: Martin L
authors.initials: ML
authors.lastname: Nielsen
authors.affiliation: Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, SE-901 85, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Nordin
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Oksanen
authors.affiliation: The Danish National Centre for Social Research, Copenhagen, DK-1052, Denmark.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Pejtersen
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Pentti
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK ; Department of Psychology, University of Turku, Turku, FI- 20014, Finland.
authors.forename: Paula
authors.initials: P
authors.lastname: Salo
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK ; Inserm U1018, Centre for Research in Epidemiology and Population Health, Villejuif, F-94807, France.
authors.forename: Archana
authors.initials: A
authors.lastname: Singh-Manoux
authors.affiliation: Folkhälsan Research Center, Helsinki, FI-00290, Finland ; Nordic School of Public Health, Göteborg, SE-402 42, Sweden ; Department of Public Health, University of Turku, Turku, FI-20014, Finland.
authors.forename: Sakari
authors.initials: S
authors.lastname: Suominen
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, SE-171 77, Sweden.
authors.forename: Töres
authors.initials: T
authors.lastname: Theorell
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Salla
authors.initials: S
authors.lastname: Toppinen-Tanner
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland ; Department of Public Health, University of Turku, Turku, FI-20014, Finland ; Turku University Hospital, Turku, FI-20520, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Vahtera
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Ari
authors.initials: A
authors.lastname: Väänänen
authors.affiliation: Occupational and Environmental Medicine, Uppsala University, Uppsala, SE- 751 85, Sweden.
authors.forename: Peter J M
authors.initials: PJ
authors.lastname: Westerholm
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, SE-171 77, Sweden.
authors.forename: Hugo
authors.initials: H
authors.lastname: Westerlund
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, SE-171 77, Sweden ; Institute of Environmental Medicine, Karolinska Institutet, Stockholm, SE-171 77, Sweden ; School of Health Sciences, Jönköping University, Jönköping, SE- 553 18, Sweden.
authors.forename: Eleonor
authors.initials: E
authors.lastname: Fransson
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Katriina
authors.initials: K
authors.lastname: Heikkilä
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland.
authors.forename: Marianna
authors.initials: M
authors.lastname: Virtanen
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, DK-2100, Denmark ; Department of Public Health and Department of Psychology, University of Copenhagen, Copenhagen, DK-1353, Denmark.
authors.forename: Reiner
authors.initials: R
authors.lastname: Rugulies
authors.affiliation: Finnish Institute of Occupational Health, Helsinki, FI-00250, Finland ; Department of Epidemiology and Public Health, University College London, London, GB-WC1E 6BT, UK ; Institute of Behavioral Sciences, University of Helsinki, Helsinki, FI-00014, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki