In shock discovery, scientists link mother’s childhood trauma to specific molecules in her breast milk

A new study published in Translational Psychiatry reports that mothers with a history of adverse childhood experiences tend to have a distinct molecular profile in their breast milk. These differences in specific microRNAs and fatty acids were also associated with aspects of their infants’ temperament in the first year of life.

A growing body of evidence suggests that the health consequences of early life stress can be transmitted across generations. Adverse childhood experiences, such as abuse, neglect, or household dysfunction, can have lasting effects on an individual’s mental and physical health. Research also indicates that children of parents who were exposed to such adversity are at a higher risk for developing their own behavioral and metabolic issues.

Scientists are working to identify the biological pathways through which these effects might be passed down. Breast milk, a complex fluid rich in bioactive compounds that influence infant development, presents a plausible route for this transmission.

“Our main motivation was to examine the relevance of breast milk to the emerging concept of ‘transgenerational trauma’. Our previous work identified a role for sperm epigenetics in potential biological transmission of psychiatric disease susceptibility through the patriline (fathers),” said study author Ali Jawaid, principal investigator at the Translational Neuropsychiatry Research Group (TREND Lab) at the Polish Center for Technology Development.

“Breast milk introduces an additional pathway that is relevant for matrilineal (mothers) influences. We wanted to test whether epigenetic signatures of adverse childhood experiences in mothers could be detected in their breast milk, and whether they are associated with early behavioral measures in their infants. This is, indeed, what the study showed.”

For their study, the researchers conducted a prospective study with 103 mother-child pairs from Wroclaw, Poland. The participants were assessed at birth, and then again at 5 and 12 months after birth. At the 5-month visit, mothers provided breast milk samples and completed questionnaires about their infant’s temperament.

At the 12-month visit, mothers completed a questionnaire to assess their own history of adverse childhood experiences before the age of 12. This timing was chosen to prevent any stress from the questionnaire from influencing the composition of the milk samples.

The research team analyzed the breast milk for two types of molecules: microRNAs, which are small molecules that help regulate which genes are turned on or off, and fatty acids, which are fundamental components of fats. The mothers were categorized into a “high adversity” group if they had experienced two or more traumatic events in childhood, and a “low adversity” group if they had experienced zero or one. The scientists then compared the molecular composition of the milk between these two groups.

The analysis revealed distinct differences in the milk’s microRNA content. Milk from mothers in the high adversity group showed elevated levels of three specific microRNAs, identified as miR-142-3p, miR-142-5p, and miR-223-3p.

Further analysis indicated a positive correlation, suggesting that as a mother’s number of adverse childhood experiences increased, the levels of these three microRNAs in her breast milk also tended to increase. These associations were present even when accounting for symptoms of postpartum depression, which did not differ between the groups.

“We were surprised that the alterations of microRNAs in milk were not mediated or confounded by postpartum depression,” Jawaid told PsyPost. “One might expect that mothers with more adverse childhood experiences would also have higher postpartum depression, and that this could explain the effects observed in milk. However, this was not the case in our cohort.”

The researchers also identified differences in the fatty acid composition of the breast milk. Specifically, mothers in the high adversity group had lower concentrations of medium-chain fatty acids in their milk compared to mothers in the low adversity group. This finding held true even after the researchers statistically controlled for other factors that could influence fatty acid levels, such as the mother’s dietary fat intake and body mass index.

“Signatures of childhood traumatic experiences can persist biologically for a long time and can be detectable even in body fluids such as breast milk,” Jawaid said. “A next step will be to examine whether enriching experiences or therapy before or during pregnancy can modify these signals.”

The researchers then explored potential links between these molecular signatures in the milk and the infants’ temperament, which was assessed through maternal reports. The results suggest a connection. For example, higher expression of miR-142-5p in breast milk was associated with infants showing more high-intensity pleasure at 12 months. At the same time, lower expression of this microRNA was linked to infants showing more distress when faced with limitations.

Similarly, the levels of medium-chain fatty acids in the milk were associated with certain infant behaviors. Higher concentrations of these fatty acids were correlated with a greater “falling reactivity,” which reflects an infant’s reaction to loss of support or balance, at 5 months of age. Other types of fatty acids in the milk were also linked to temperamental traits such as activity level and soothability at 12 months.

“Epigenetic signatures in milk were associated with different early temperaments in newborns,” Jawaid told PsyPost. “However, this should NOT be interpreted as breastfeeding being harmful. Breast milk is protective in many ways. We need more work to clarify whether these epigenetic signals in the milk that are impacted by mothers’ childhood adversity are just biomarkers or transmit risk or adaptability and resilience to the next generation.”

The authors note some limitations of their work. The findings are based on correlations, which means the study identifies associations but cannot prove that the changes in breast milk directly cause the differences in infant temperament. The study was also conducted with a specific group of participants from an urban Polish population, so the results may not apply to all populations.

“The study involved 103 mother child dyads from a highly educated urban Polish cohort, so the implications should be interpreted with nuance,” Jawaid noted. “Still, the findings show that maternal adverse childhood experiences are associated with measurable epigenetic alterations in human breast milk, and that these signatures relate to early infant behavioral profiles.”

The researchers also emphasize that these findings should not be interpreted to discourage breastfeeding, as breast milk provides numerous established benefits for infant health. The study instead points to early life trauma as a public health issue with long-lasting biological consequences, highlighting the need to develop strategies that might mitigate the transmission of risk across generations.

“This study should not be misused to blame mothers or to argue for formula feeding,” Jawaid explained. “Breast milk provides many protective factors, and we cannot say — at this point — that altered epigenetic factors in milk lead to psychiatric disease risk. Importantly, our previous work has also identified trauma related epigenetic changes in sperm. The biological and psychosocial contributions of both mothers and fathers matter. Trauma is the problem, not mothers or fathers.”

For future research, the scientists are planning studies with animal models to better understand the potential causal links between milk components and offspring outcomes. They are also continuing to follow the children from this study as they grow older to see how these early associations relate to later health and behavior.

“Our long-term goal is to identify biomarkers and mechanisms of intergenerational transmission of psychiatric disease risk in humans,” Jawaid said. “We are following this cohort longitudinally, and are studying parallel cohorts in Bosnia, Pakistan, and Rwanda. Ultimately, we hope to develop biomarkers, guidelines and mitigation strategies to prevent the transmission of psychiatric risk across generations.”

The study, “Differential microRNAs and metabolites in the breast milk of mothers with adverse childhood experiences,” was authored by Weronika Tomaszewska, Anna Apanasewicz, Magdalena Gomółka, Maja Matyas, Patrycja Rojek, Marek Szołtysik, Magdalena Babiszewska-Aksamit, Bartlomiej Gielniewski, Bartosz Wojtas, Anna Ziomkiewicz and Ali Jawaid.