Background Occupational stress has been shown to be an important factor affecting the mental health of workers. The role of affective commitment to the organization and overcommitment to work cannot be ignored. However, there is a lack of research on this topic in China.

Objective To explore a potential mediating effect of affective commitment on how occupational stress affects the mental health of medical staff and a potential moderating effect of overcommitment on the mediating effect of affective commitment.

Methods A total of 1372 health care workers in a tertiary Grade A hospital in Lanzhou City were selected as study subjects for a cross-sectional survey. The occupational stress, emotional commitment, and psychological distress of the subjects were evaluated by the Effort-Reward Imbalance Scale, Affective Commitment Scale, and Kessler 10 Scale. SPSS 26.0 was used for correlation analysis, mediation analysis, and moderated mediation analysis. Common method bias wasevaluated by Harman one-factor test.

Results A total of 1372 questionnaires were distributed, of which 1277 valid questionnaires were returned, with a valid recovery rate of 93.08%. The mean occupational stress score was 1.14±0.23, the mean overcommitment score was 20.26±3.21, the mean affective commitment score was 20.25±3.34, and the mean psychological distress score was 26.26±7.90. The Spearman correlation analysis results showed that occupational stress among medical staff was positively correlated with overcommitment and psychological distress (r=0.153, 0.410, P＜0.01) and negatively correlated with affective commitment (r=−0.341, P＜0.01); overcommitment was negatively related to affective commitment and positively related to psychological distress (r=−0.107, 0.312, P＜0.01); affective commitment was negatively related to psychological distress (r=−0.464, P＜0.01). The positive effect of occupational stress on psychological distress of medical staff was significant (b=0.41, t=15.42, P<0.001); affective commitment presented a partial mediating effect on the relationship between occupational stress and psychological distress (effect value=0.13), accounting for 31.71% of the total effect; overcommitment moderated the process of occupational stress-affective commitment-psychological distress (P＜0.01).

Conclusion Affective commitment of medical staff has a partial mediating effect on the relationship between occupational stress and psychological distress, and overcommitment plays a significant role in moderating the process of occupational stress-affective commitment-psychological distress.