Objectives It is debated if results from epidemiological studies on psychosocial factors at work and risk of depression are affected by the common rater problem, thus inflating associations by introducing reporting bias. Because depression is associated with cognitive distortions it is expected that severity of depression affects the level of reported exposures. The present study aims to investigate the possible dose-effect relationship between diagnosed severity of depression and differences between individual and work-unit averaged measures of the psychosocial work environment in a large epidemiological study.
Methods In 2007 4291 Danish public employees within 378 different work units were enrolled in the study. Mean levels of psychological demands were computed for each work unit. Screening for depressive symptoms (SCL-DEP6) 329 persons scoring above cut-off were invited to a diagnostic interview (SCAN), resulting in 40 cases with mild, 43 with moderate, and 17 with severe depression, and 229 cases with no diagnosis of depression. Differences were analysed with ANOVA statistics.
Results For quantitative demands the mean score difference was 0.08 points for participants with mild depression compared to their work-unit average, 0.28 points for participants with moderate depression and 0.36 points for participants with severe depression (p = 0.40).
Conclusions The data indicate a dose-effect pattern between severity of depression and divergence from work-unit averages. However, the results are not statistically significant and our initial hypothesis is not supported. Future perspectives involve including two follow-up waves to gather more cases and provide additional statistical power, and also allow adjustment for relevant confounders and changes in reporting over time. These results have implications regarding the need for exposure measures that are independent of reports from participants diagnosed with depression, but may also be explored as indicators of social marginalisation as a mechanism relevant to the development or maintenance of depression.