Objective To investigate the mental health status of researchers in Huairou Science City and to analyze the impact and pathways of salivary cortisol (COR), occupational stress, and burnout on depression.

Methods From July to September 2023, 420 researchers in Huairou Science City were selected as study subjects by a cluster random sampling method. Their occupational stress, burnout, and depression were surveyed with questionnaires, while salivary cortisol concentrations were measured. Amos 26.0 software was used to construct a chain mediation model to verify the pathway effects of salivary cortisol, occupational stress, and burnout on depression, and the bootstrap method was used to verify mediation effects.

Results A total of 414 valid questionnaires were collected, with a response rate of 98.57%. The median concentration of salivary COR among the 414 researchers was 12.57 nmol/L. The rate of occupational stress was 38.89% (161/414), the rate of high occupational burnout was 30.19% (125/414), and the rate of depression was 21.50% (89/414). The researchers with a monthly salary below 9 000 RMB, or weekly working hours longer than 40 hours, or aged 30-40 years, had higher salivary COR concentrations (all P < 0.05); the researchers aged ≤ 30 years, or with bachelor's degrees, or married/cohabiting, or with a monthly salary below 9 000 RMB, or with weekly working hours longer than 40 hours had higher levels of occupational burnout (all P < 0.05); The researchers aged 31-40 years, or with a doctorate, or with weekly working hours longer than 40 hours, or with a monthly salary below 9 000 RMB, had higher levels of occupational stress (all P < 0.05); the researchers those aged ≤ 30 years, or with a master's degree and lower, or with a monthly salary below 9 000 RMB, or with weekly working hours longer than 40 hours had higher depression scores (all P < 0.05). Mediation model results showed that occupational stress had no direct predictive effect on depression but influenced depression indirectly through two pathways: occupational stress → salivary COR → depression and occupational stress → salivary COR → occupational burnout → depression, with effect sizes of 80.80% and 10.40%, respectively.

Conclusions The levels of occupational stress, burnout, and depression among researchers in Huairou Science City cannot be ignored. The impact of occupational stress on depression was primarily mediated by intermediate variables. Managers should take necessary measures to reduce occupational burnout to mitigate depressive symptoms. The role of physiological indicators such as salivary COR in the mediation effect should be paid attention in order to fully understand the effect mechanisms of occupational stress on mental health.