The infant gut microbiome and the intergenerational transmission of psychiatric risk.

Elevated stress during the prenatal period is associated with increased psychiatric risk among children. However, less is known about the mechanisms through which this intergenerational transmission of risk occurs. The early life microbiome is one candidate mechanism through which maternal stress during the prenatal period could impact offspring mental health, with a growing body of literature highlighting the importance of the early life microbiome in mental health across the lifespan. This study leverages Canada's largest deeply phenotyped birth cohort to elucidate the mechanistic associations between maternal prenatal stress, dynamic changes in the microbiome across the first year of life, and child internalizing symptoms. Analytic sample size with use of full information maximum likelihood methodology was 2,985. Analyses indicated that early diversification of the early life microbiome significantly mediated the relation between higher maternal perceived stress during pregnancy and increased internalizing symptoms among offspring at 5 years of age. Crucially, microbial taxa impacted by early diversification of the microbiome implicated the immune system. This work supports maturational dynamics of the microbiome as one mechanism through which prenatal stress is biologically embedded to impact offspring's later mental health. By linking several burgeoning areas of research, this study lays the groundwork for future multidisciplinary work examining the intergenerational transmission of psychiatric risk through the microbiome.