Exhaustion, Not Low Engagement, Differentiates Work-Related and Non-Work-Related Depression in Korean Wage Workers: A Negative-Control Analysis.

Background/Objectives: Workplace mental health surveys routinely measure exhaustion and work engagement, but whether either distinguishes work-attributed depression from depression in general remains unclear. We examined this question among Korean wage workers using a negative control outcome design. Methods: We analyzed the seventh Korean Working Conditions Survey (2023), a nationally representative sample of wage workers (complete-case N = 25,776; 270 work-related and 271 non-work-related depression cases). Past-year depression was classified by workers' attribution, with non-work-related depression as the negative control outcome. This control shares the respondent, instrument, and reporting occasion-and thus the principal reporting biases-but is presumed not to be reachable through an occupational pathway. For each exposure, we estimated the specificity contrast and assessed robustness across adjustment models, propensity-score matching, and stratification. Results: The exposures showed a double dissociation. Exhaustion was associated with both depression types, but was more strongly with work-related depression (fully adjusted specificity odds ratio, 1.17 per point; 95% confidence interval, 1.01-1.36), increasing monotonically with severity. Engagement was inversely associated with both, but did not distinguish them (0.97; 0.88-1.07). The dissociation persisted across all adjustment and sensitivity models and under propensity-score matching, where exhaustion did not distinguish between non-work-related depression and no depression-the expected negative-control behavior. Conclusions: Exhaustion, but not low engagement, distinguished work-attributed from non-work-attributed depression and may serve as a discriminating surveillance indicator. These cross-sectional associations are consistent with occupational specificity, but cannot establish causality, and they rely on single-item self-reported measures in small subgroups. Thus, replication with validated instruments and longitudinal data is required.