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ABSTRACTBackground: Structural and functional changes in stress-related gray matter (GM) regions have been found in trauma-exposed individuals. However, the nature of underlying neurobiological abnormalities in individuals following stress, particularly acute stress, is unclear.Methods: In this study, thirty-two motor vehicle accident (MVA) survivors and thirty-one nonexposed controls were recruited. MVA survivors were scanned and received trauma-specific clinical assessments within one week of their accident. Mean diffusivity (MD), fractional anisotropy (FA), and GM volume (GMV) were measured as indicators of GM structural changes in the medial orbitofrontal cortex (mOFC), amygdala, hippocampus, insula, and anterior cingulate cortex (ACC) bilaterally. In these regions with significant structural changes in the MVA group, sex differences were assessed. Functional connectivity (FC) analysis was conducted to explore the brain network effect of these structural alterations. Correlation analyses were performed to explore the association between the resultant GM structure and anxiety symptoms.Results: Significantly lower fractional anisotropy (FA) in the mOFC and ACC was detected in the MVA group. In these regions, females in the MVA group had lower MD in the right ACC, but no sex-by-stress interactions were found. Compared with controls, the MVA group had less connectivity between the right mOFC and the left inferior OFC. No significant association was found between GM structure and anxiety symptoms.Conclusion: MVA survivors showed potential GM microstructure alterations which may affect functional consequences shortly after acute stress. These findings may contribute to informing future strategies for timely interventions after acute stress.