Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts [v2; ref status: indexed, http://f1000r.es/30q]

• Main Authors: Ida E. H. Madsen, Harald Hannerz, Solja T. Nyberg, Linda L. Magnusson Hanson, Kirsi Ahola, Lars Alfredsson, G. David Batty, Jakob B. Bjorner, Marianne Borritz, Hermann Burr, Nico Dragano, Jane E. Ferrie, Mark Hamer, Markus Jokela, Anders Knutsson, Markku Koskenvuo, Aki Koskinen, Constanze Leineweber, Martin L. Nielsen, Maria Nordin, Tuula Oksanen, Jan H. Pejtersen, Jaana Pentti, Paula Salo, Archana Singh-Manoux, Sakari Suominen, Töres Theorell, Salla Toppinen-Tanner, Jussi Vahtera, Ari Väänänen, Peter J. M Westerholm, Hugo Westerlund, Eleonor Fransson, Katriina Heikkilä, Marianna Virtanen, Reiner Rugulies, Mika Kivimäki, for the IPD-Work Consortium
• Format: Article
• Language: English
• Published: F1000 Research Ltd 2014-02-01
• Series: F1000Research
• Subjects: Epidemiology; Methods for Diagnostic & Therapeutic Studies; Mood Disorders; Social & Behavioral Determinants of Health; Statistical Methodologies & Health Informatics
• Online Access: http://f1000research.com/articles/2-233/v2

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.   Discussion: 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.