International university students may be at greater risk for developing psychological problems due to the unique stressors in them, particularly during the COVID-19 pandemic. The purpose of present study is to propose and test a moderated mediation model that would illuminate the underlying relationships of cross-cultural adaption, perceived stress and psychological health as well as the moderating effect of optimism and resilience among international medical undergraduates in China during the COVID-19 pandemic. The study was conducted via a web-based survey in November 2020. Electronic informed consents were obtained from all participants. A total of 453 students including 233 males and 220 females aged 18 to 28 years with an average age of 22.09 ( = 2.73) completed the questionnaires. Symptom Checklist 90, the measurement of cross-cultural adaption, the Perceived Stress Scale, the Life Orientation Test-Revised and the Resilience Scale were used for the survey. Results for the moderated mediation model testing revealed that cross-cultural adaption significantly and negatively associated with the Global Severity Index (GSI) of the Symptom Checklist 90 (β = -0.24, < 0.01), and perceived stress partially mediated the relationship. Optimism (β = -0.29, < 0.01) and confidence in COVID-19 control (β = -0.19, < 0.01) had direct negative effects on perceived stress. Furthermore, optimism and resilience negatively moderated the indirect effect of cross-cultural adaption on psychological health through perceived stress. Findings of this study suggest that university educators ought to promote or make use of programs that cope with stress and boost optimism and resilience in order to support students not only adapt well to a new culture, but also keep good psychological health during the period of COVID-19 pandemic.
