The role of job strain in the relationship between depression and long-term sickness absence: a register-based cohort study.

Purpose: Though individuals with depression and those with poor working conditions are more likely to be on long-term sickness absence (LTSA), less is known about how working conditions may modify the associations between depression status and LTSA. This study aims to examine the association between depression and LTSA among Swedish workers with different levels of job strain and its individual components (job demands and job control).

Methods: All Swedish workers 30 - 60 years old (N = 3,065,258) were studied in 2005. At baseline (2005-2010), workers were categorized as: without depression, being prescribed antidepressants, and being in inpatient/outpatient care. Job strain was measured using a Swedish Job Exposure Matrix, and data on LTSA were obtained from 2011 to 2021. The association between depression and LTSA was assessed using Cox proportional-hazards regression stratified by categories of job strain.

Results: Compared to workers without depression, workers with depression had higher risk of LTSA across all job strain levels. Depression was associated with the highest hazards of LTSA in active jobs, but a similar population attributable fraction (PAF) was found across categories of job strain, indicating similarities between the different categories.

Conclusion: There was evidence of a moderating effect of job strain in the relationship between depression and LTSA, but also evidence that this was due to differences in baseline depression prevalence in the different job strain categories. Future research is needed to determine alternative factors which could be relevant for reducing LTSA among those who have already developed depression.