Objective  To explore the mediating effect of depressive symptoms on occupational stress and work-related musculoskeletal disorders (WMSDs) in employees of petrochemical enterprises for developing intervention measures on WMSDs.

  Methods  Totally 4 066 employees were recruited with cluster sampling from a petrochemical enterprise in Jiangsu province for an online survey conducted during July – October 2021. Core Occupational Stress Scale (COSS), Patient Health Questionnaire-9 (PHQ-9), and two questionnaire on demographics and WMSDs developed by Chinese researchers previously were used in the survey. Spearman rank correlation analysis was adopted to analyze the relationships between occupational stress, depression symptoms, and WMSDs; hierarchical regression analysis and bootstrap method were used to verify the mediating effect of depressive symptoms on the correlation between occupational stress and WMSDs.

  Results  Of the 3 763 participants with valid responses, 2 934 (77.97%) were assessed as having WMSDs during past one year. The participants′ mean scores were 3.47 ± 3.17 on WMSDs and 10.04 ± 5.99 on depressive symptoms; the mean score on occupational stress was 45.79 ± 9.48, with the dimensional scores of 19.81 ± 3.75 on social support, 15.85 ± 4.94 on organization and reward, 12.35 ± 3.39 on demand and effort, and 4.62 ± 1.80 on autonomy, respectively. Spearman rank correlation analysis revealed following significant correlations among partici-pants′ scores on WMSDs, occupational stress and its dimensions, and depression symptoms: (1) positive correlations of WMSDs with overall occupational stress (r = 0.334), occupational stress dimensions of organization and reward (r = 0.284) and demand and effort (r = 0.202), and depression symptoms (r = 0.463) (P < 0.01 for all); (2) negative correlations of WMSDs with occupational stress dimensions of social support (r = – 0.256) and autonomy (r = – 0.141) (both P < 0.01); (3) positive correlations of depression symptoms with overall occupational stress (r = 0.621), occupational stress dimensions of organization and reward (r = 0.540) and demand and effort (r = 0.410) (P < 0.01 for all); (4) negative correlations of depression symptoms with social support (r = – 0.419) and autonomy (r = – 0.196) (both P < 0.01); (5) positive correlations of overall occupational stress with occupational stress dimensions of organization and reward (r = 0.848) and demand and effort (r = 0.639) (both P < 0.01); and (6) negative correlations of overall occupational stress with occupational stress dimensions of social support (r = – 0.648) and autonomy (r = – 0.310) (both P < 0.01). The results of mediating effect analysis showed that depressive symptoms had a partial mediating effect on the correlations of WMSDs with occupational stress dimensions of social support (effect value = – 0.137; confidence interval CI: –0.155, – 0.120; effect percentage = 72.87%) and demand and effort (effect value = 0.177; CI: 0.159, 0.196; effect percentage = 78.67%) but a complete mediating effect on the correlations of WMSDs with occupational stress dimensions of organization and reward (effect value = 0.146; CI: 0.131, 0.160; effect percentage = 90.12%) and autonomy (effect value = – 0.126; CI: – 0.158, – 0.094; effect percentage = 98.44%).

  Conclusion  Among the employees in a petrochemical enterprise in a province of China, the detection rate of WMSDs was high and depressive symptoms showed a mediating effect on the correlation of occupational stress with WMSDs, suggesting that the prevalence of WMSDs could be decreased through intervention on depression symptoms in the occupational population.