The purpose of this study was to explore the association between perceived stress and depression among medical students and the mediating role of insomnia in this relationship during the COVID-19 pandemic in China.
A cross-sectional survey was conducted from March to April 2020 in medical university. Levels of perceived stress, insomnia and depression were measured using Perceived Stress Scale (PSS), Insomnia Severity Index (ISI) and Patient Health Questionnaire 9 (PHQ-9). The descriptive analyses of the demographic characteristics and correlation analyses of the three variables were calculated. The significance of the mediation effect was obtained using a bootstrap approach with SPSS PROCESS macro.
The mean age of medical students was 21.46 years (SD=2.50). Of these medical students, 10,185 (34.3%) were male and 19,478 (65.7%) were female. Perceived stress was significantly associated with depression (β=0.513, P < 0.001). Insomnia mediated the association between perceived stress and depression (β=0.513, P < 0.001). The results of the non-parametric bootstrapping method confirmed the significance of the indirect effect of perceived stress through insomnia (95% bootstrap CI =0.137, 0.149). The indirect effect of insomnia accounted for 44.13% of the total variance in depression.
These findings contribute to a better understanding of the interactive mechanisms underlying perceived stress and depression, and elucidating the mediating effects of insomnia on the association. This research provides a useful theoretical and methodological approach for prevention of depression in medical students. Findings from this study indicated that it may be effective to reduce depression among medical students by improving sleep quality and easing perceived stress.

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