Perceived Stress in First-Year Medical Students and its Effect on Gut Microbiota

Medical students are constantly under stress caused by strenuous medical programs, which may exert persistent physical and psychological effects on their well-being. Using medical students as a model population, this work explores the gut microbiome as a potential contributing mechanism for why individuals exposed to similar stimuli react variably. We evaluated the relationship of gut microbiome composition of first year medical students and stress resilience over a period of 4 months. Our objective was to identify gut microbiome characteristics of individuals that showed long-term stress resilience. Students were voluntarily recruited and screened for lifestyle and environmental factors at 3 timepoints during the first semester. Fecal samples were also collected at each timepoint. In order to identify candidates with stress resilience, their perceived stress and depression levels were normalized and summed to produce a psychologic index score. The most notable finding is a correlation between psychologic resiliency of Bacteriodete:Firmicute abundance as well as a relationship between durable resiliency and microbiome stability. Phylogenetic assembly of participants by microbiome relatedness found that 100% of subjects who were resilient to stress across all timepoints (n=8) were phylogenetically clustered in adjacent positions, showing a high degree of temporal stability. Of participants who were not durably resilient to stress, only 62% of participants (n=8) showed microbiomes that were phylogenetically related across the same 4 month period. We identified 2,102 Operational Taxonomic Units (OTUs) which were unique to the durable resilience group and 94 OTUs which were unique to the susceptible group. Of the 4,794 observed OTUs, 6.1% (n=294) were significantly different between groups. These findings support that the gut microbiome may play an important role in stress resilience at a time scale of 4 months. A better understanding of the role of the gut microbiome in stress resilience may shed light on potential treatment to reduce stress/anxiety in general, as well as to promote wellbeing of our future health care providers and physicians.