Integrating gut microbiota and violence exposure metrics to classify psychological distress in middle-aged adults

Background: Exposure to violence and psychological distress are positively correlated across populations. Microbiota-gut-brain crosstalk research supports that the microbiota is affected by environmental stressors and may influence mental state. Accordingly, we explored how the microbiota relates to exposure to violence and distress in midlife, a pivotal yet underexplored period. This life stage is marked by emerging vulnerability to chronic stress and mental health decline yet offers opportunities for early identification and intervention. Methods: We characterized the fecal microbiota of a previosly snowball-recruited Israeli-Muslim cohort (n = 305, 40-65 yrs) exposed to ongoing and increasing violence (during adulthood) and examined correlations with subjective reports of exposure to violence and psychological distress. We then used machine learning to leverage microbiota profiles and exposure to violence, classifying individuals into high- and low-distress categories. Results: We identify unique microbial signatures associated with increasing exposure to violence and distress. Some associated bacteria were previously identified in the literature, while others were not yet described in the context of the gut-brain axis. Microbial profiles associated with violence and distress are largely non-overlapping, yet we are able to classify participants into high- and low distress categories using a combination of microbiota and violence variables. This combined model outperforms those using only microbiota or demographics, but its classification accuracy remains modest (with a median area-under-the-curve of 0.595 (IQR 0.045). Conclusions: This research sheds light on the microbiota-gut-brain axis, highlighting that psychological distress and exposure to violence are differentially associated with microbiota composition in midlife. These cross-sectional findings, together with moderate classification into distress classes based on the microbiome, suggest that holistic, context-aware approaches would benefit proactive mental health interventions.