Perceived Stress and Psychological Distress among Chinese Nurses: The Mediating and Moderating Roles of Psychological Flexibility and Insomnia

Background Nurses working in high-stress clinical environments are particularly vulnerable to psychological distress. While perceived stress plays a central role in psychological distress, the mechanisms underlying this association remain unclear. Methods A cross-sectional study was conducted with a sample of 2,951 nurses in China. Psychological distress was measured using the Kessler Psychological Distress Scale, perceived stress using the Chinese Perceived Stress Scale, psychological flexibility using the Comprehensive Assessment of ACT Processes, and insomnia using the Insomnia Severity Index. Descriptive statistics, Pearson correlations, and moderated mediation analyses using Hayes' PROCESS macro were employed for data analysis. Results Moderate to severe psychological distress was observed in 62.2% of nurses. Perceived stress was strongly and positively correlated with psychological distress (r = 0.75, p < .01), whereas psychological flexibility was negatively correlated with both perceived stress (r = -0.72, p < .01) and psychological distress (r = -0.68, p < .01). The results of the mediation analysis showed that psychological flexibility mediated 47.64% of the total effect of perceived stress on psychological distress. Moderation analysis showed that insomnia intensified both the direct effect of perceived stress on psychological distress (β _{non−insomnia}  = 0.25, t = 20.92, p < .001; β _insomnia  = 0.33, t = 22.68, p < .001) and the indirect effect of psychological flexibility on psychological distress (β _{non−insomnia} = -0.12, t = -10.82, p < .001; β _insomnia = -0.17, t = -11.61, p < .001), with stronger associations observed in the insomnia group compared to the non-insomnia group. Conclusions The findings revealed a high prevalence of psychological distress among nurses. Perceived stress was significantly correlated with psychological distress, and psychological flexibility mediated this association. Furthermore, insomnia moderated the effect of perceived stress on psychological distress and the impact of psychological flexibility on psychological distress. These findings underscored the importance of targeted interventions addressing sleep disturbances and enhancing psychological flexibility to mitigate psychological distress, particularly in high-stress professions such as nursing. Trial registration: The study was approved by the Ethics Committee of the Health Science Center, Xi’an Jiaotong University (No. 2020–1336), and complied with the Declaration of Helsinki.