BackgroundWith the rapid development of the networking technologies， internet addiction has increasingly become a serious mental health issue. Previous studies have revealed the link between childhood trauma and internet addiction， while the mediating role of perceived stress in this link is not yet clear. ObjectiveTo investigate the role of medical students' perceived stress in the relationship between childhood trauma and internet addiction， so as to provide references for the intervention of internet addiction. MethodsFrom February to March 2023， a random sampling technique was used to select 1 232 undergraduate students from the School of Clinical Medical Sciences of Southwest Medical University as research subjects. The Childhood Trauma Questionnaire-Short Form （CTQ-SF）， Perceived Stress Scale （PSS）， Internet Gaming Disorder Scale （IGDS）， and Bergen Social Media Addiction Scale （BSMAS） were used for assessment. Pearson's correlation coefficients were calculated. The mediation effect of perceived stress in the relationship between childhood trauma and internet addiction was tested using Model 4 in the SPSS Process 4.1， and Bootstrapping procedure involving 5 000 replicates was employed to confirm the statistical significance. ResultsA total of 1 016 （82.47%） valid completed questionnaires were gathered. The CTQ-SF scores of medical students were positively correlated with PSS scores， IGD scores， and BSMAS scores （r=0.583， 0.474， 0.465， P<0.01）. PSS scores were positively correlated with IGD scores and BSMAS scores （r=0.369， 0.479， P<0.01）. Childhood trauma in medical students was found to positively predict perceived stress （β=0.191， P<0.01）， social media addiction （β=0.160， P<0.01）， and internet gaming disorder （β=0.106， P<0.01）. Perceived stress played a significant mediating role in the relationship between childhood trauma and internet gaming disorder， indirect effect value was 0.018 （95% CI： 0.009~0.027）， accounting for 16.98%. Perceived stress also exhibited a significant mediating role in the relationship between childhood trauma and social media addiction， indirect effect value was 0.063 （95% CI： 0.048~0.079）， accounting for 39.38%. ConclusionChildhood trauma in medical students may affect internet gaming disorder and social media addiction through perceived stress. ［Funded by 2022 Annual Research Project of Sichuan Applied Psychology Research Center，（number，CSXL-22102）］