Abstract
The gut microbiota plays a role in a wide range of diseases and disorders, with low microbial diversity and richness emerging as notable risk factors. This longitudinal study addressed the impact of marital quality (assessed by the Couples Satisfaction Index) on changes in depressive symptoms, and gut diversity, richness, and permeability. On two occasions an average of 90 days apart, 162 people provided stool and blood samples, and completed questionnaires. Depressive symptoms, assessed by the Center for Epidemiological Studies Depression Scale (CES-D), increased from visit 1 to visit 2 in those with clinically significant relationship problems, in contrast to the lack of change among their more satisfied counterparts. These changes in depression were consequential: the gut microbiota's diversity and richness decreased in tandem with the increase in depressive symptoms. Lower relationship satisfaction also foreshadowed increases in lipopolysaccharide binding protein from visit 1 to visit 2, reflecting greater translocation of bacterial endotoxin from the gut to blood circulation, a process that fuels inflammation. Lower diversity and richness provide a pathway from depressive symptoms and marital distress to subsequent health risk.