Postnatal depression may affect children's brain development through breast milk, study finds

Postnatal depression may affect children's brain development through breast milk, study finds

A study involving mice suggests biological changes in breastmilk linked to postnatal depression could affect brain development, learning and memory, highlighting the importance of early diagnosis and treatment.

Postnatal depression may affect more than a mother's mental health, with new research suggesting that biological changes in breast milk could influence how a child's brain develops.

The findings highlight the importance of identifying and treating depression after childbirth, particularly during the early months when infants depend heavily on their mothers for feeding and care.

The study, published in the journal Cell and reported through EurekAlert, examined how biological substances in breast milk from mothers experiencing postnatal depression could affect the developing brains of their offspring.

Postnatal depression is a mental health condition that develops after childbirth and can affect a mother's mood, sleep, emotions and ability to cope with everyday activities. It is estimated to affect between 10 and 20 per cent of women worldwide.

Previous studies have linked the condition to difficulties in children's language and cognitive development, behavioural regulation and academic performance. Children whose mothers experience postnatal depression may also face a higher risk of depression during adolescence.

Although these effects have often been associated with genetic factors, pregnancy-related conditions and interactions between mothers and their children, the biological processes behind the long-term impact have remained unclear.

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The latest research explored whether breast milk could provide one of the pathways through which a mother's mental health influences her child's development.

Breast milk supplies infants with essential nutrients for growth, but it also contains biological substances that help regulate various processes in the body. Researchers focused on tiny particles known as extracellular vesicles, which transport genetic material and other substances between cells.

Using mice, the research team conducted experiments in which healthy mothers and mothers displaying depression-like symptoms exchanged their young.

They found that pups born to healthy mothers but nursed by mothers in the depression model developed more noticeable cognitive and emotional difficulties than those born to depressed mothers but nursed by healthy mothers.

The findings suggested that the breastfeeding environment played an important role in the development of the young animals.

Further examinations revealed that pups nursed by mothers in the depression model had shorter and less developed branches in newly formed neurons in the hippocampus, a region of the brain responsible for learning and memory.

Researchers also observed changes in communication between brain cells. Some abnormalities appeared as early as 21 days after birth and remained evident when the animals reached adulthood.

The team subsequently examined the contents of breast milk vesicles and discovered increased levels of three particular microRNAs, known as miR-15a-5p, miR-15b-5p and miR-205-5p.

MicroRNAs are tiny molecules that help regulate how genes function. Researchers found that these molecules were carried inside breast milk vesicles and could reach different regions of the pups' brains, including areas involved in memory, learning and emotional regulation.

The findings suggested that breast milk could serve as a communication pathway between mothers and their offspring.

“Breast milk vesicle miRNAs can serve as carriers of maternal environmental signals,” the researchers explained, suggesting that changes in a mother's condition could be communicated to her offspring through breastfeeding.

To establish whether the vesicles were responsible for the observed changes, the team administered breast milk vesicles from mothers in the depression model to healthy pups.

The animals subsequently developed cognitive difficulties after weaning. However, breast milk samples from which the vesicles had been removed did not produce the same effects.

Researchers also reduced the release of these particles from the mammary glands of mothers in the depression model. This helped reduce some of the developmental abnormalities observed in their offspring.

Further investigations identified a brain receptor known as mGluR8, which helps regulate communication between nerve cells.

The researchers found that microRNAs carried in breast milk vesicles reduced the activity of this receptor in specific brain cells involved in memory formation.

When they increased the receptor's activity in the affected brain cells, some of the behavioural and neurological abnormalities improved.

However, the findings are based on experiments involving mice and do not establish that the same process occurs in human infants. Further studies involving mothers and children are needed to determine whether similar changes in breast milk microRNAs are associated with children's development.

The researchers cautioned against interpreting the findings as a reason for mothers experiencing postnatal depression to stop breastfeeding. They noted that “mothers with postnatal depression can generally continue breastfeeding and should receive timely treatment and feeding support suited to their circumstances.”

Instead, the findings highlight the importance of identifying and treating postnatal depression early while ensuring mothers receive appropriate psychological, medical and family support after childbirth.

For women struggling with depression after delivery, access to mental health care is essential not only for their recovery but also for supporting their children's well-being.

The research adds to growing evidence of the importance of maternal mental health and reinforces the need for families and healthcare systems to take postnatal depression seriously.