What Does the Microbiome Have to Do with Stress and Depression?


By Andrew Schwartz

In one aspect of her most recent National Institutes of Health (NIH)-funded research, the UC San Francisco School of Nursing’s Sandra Weiss, the Robert C. and Delphine Wentland Eschbach Chair in Mental Health, has sought to understand the effects of maternal depression and corticosteroids during pregnancy on how preterm infants manage stress early in life. The work has led Weiss to begin an innovative study that explores whether the microbiome could be a mediating factor for those infant exposures. A preliminary analysis of data from 50 infants during their first two to three weeks of life has already yielded some intriguing results.

“The microbiome of babies whose mothers are depressed during pregnancy is depleted of many important bacteria that may have beneficial effects for the infant’s well-being,” says Weiss. “We found similar effects for infants whose mothers had received corticosteroids during pregnancy.”

Weiss and her team are beginning to map the differences and, she says, “This initial data confirms for me the importance of this research and our need to continue to study the microbiome as the child develops.” In addition, the work is spawning other studies from School faculty in the Weiss Stress and Depression Research Lab. All of the work is in collaboration with the School of Medicine’s Susan Lynch, a molecular microbiologist who runs one of the country’s leading labs for the study of human microbiomes and their environments. “Sue is a very gifted, insightful colleague. We are both interested in the effects of early exposure to stressors, so our research collaboration is ideal,” says Weiss.

The Microbiome and Infant Stress Response

Ultimately, Weiss and her team will collect data from approximately 150 infants during their first two to three weeks of life, as well as at six months and 12 months of age. The research team is trying to determine if maternal depression, stress and/or corticosteroid exposure during pregnancy are linked with the proliferation or depletion of specific microbiota and any imbalance in beneficial versus pathogenic bacteria. The researchers theorize that a less diverse or unbalanced microbiome can have lasting effects on a child’s ability to react appropriately to stress.

“We have already found that stress-related hormones a mother secretes in response to her own psychological distress, as well as prescribed antenatal corticosteroids, appear to suppress the infant’s stress response,” Weiss says.

Two of the key biomarkers that Weiss will try to link to changes in the microbiome are telomere length – telomeres are caps at the ends of each strand of DNA, which protect the chromosomes and affect the integrity of cells – and cortisol reactivity to stressors, a marker of how effectively the infant’s hypothalamic-pituitary-adrenal (HPA) axis is developing. The HPA axis is responsible for releasing the appropriate stress-related hormones in response to environmental stimuli. In preterm infants, the HPA axis is still developing, so problems in its function could have lifelong implications for how the child copes with stress.

Weiss says if her work and that of others can characterize the links among maternal depression, corticosteroids, the microbiome and infant stress, it could open doors to more effective ways to support and advise mothers to prevent any adverse impact on their children. The findings can also inform studies of probiotic therapies during pregnancy and the postpartum period.

Read the full story on our Science of Caring publication.