Does stress affect your breast milk letdowns or supply?

Stress doesn't directly interfere with your letdown

Even though you might often hear it said that stress can interfere with letdowns, there's no good reason - nor reliable evidence - to suggest this is the case.

• Chronic stress affects the function of our body and neurohormonal secretions in many different ways. However,

• Believing that stress directly interferes with letdowns is like believing that stress interferes with your capacity to secrete bile into your bile duct, or acid into your stomach, or sebaceous sebum from your skin's oil glands, or pancreatic enzymes into your pancreatic duct. I disagree that psychological stress or nipple and breast pain directly impacts on milk production, and there is no evidence to suggest that this is the case.

• Often when researchers or health professionals note links between stress hormones and breastfeeding, association is accidentally mixed up with causation. The way hormones like oxytocin and prolactin act in our bodies are very complex, their interactions with measurable stress hormones like cortisol are also complex.

It’s true that catastrophic physical stress from severe injury or a serious medical condition can impact on the capacity of a gland to secrete. But overall, it is much more likely that behaviours associated with being stressed affect your breastfeeding and the amount of milk your baby is transferring, rather than the stress itself.

Stress doesn't affect your milk supply because it affects your hormone levels

You might hear it said that stress causes an increase in your cortisol levels, which decreases your prolactin levels, which means that your body makes less milk for your baby.

However, whilst your breasts need high prolactin levels at birth to get started with breastfeeding, from then the amounts of prolactin in your bloodstream don't correlate with the amount of milk your breasts make. The amount of milk your breasts make mostly depends on how much milk is removed from your breasts. So high cortisol levels don't decrease your breasts capacity to produce milk.

Stress might interfere with breastfeeding because feeling stressed changes behaviours and neuromuscular dynamics

Stress does change our behaviours, however. For example, stress might affect how you go about breastfeeding in two main ways - by changing

1. How often you offer the breast to your baby

2. How well baby fits into your body.

Both of these behaviours directly affect your breast milk supply. Pain in particular will affect how often you can offer the breast, and how you hold your baby to the breast. Pain requires urgent attention so that you can get rid of the underlying nipple and breast tissue drag.

Stress can result in breastfeeding problems, because feeling stressed might

• Interfere with you offering frequent and flexible feeds

• Result in you tightening up your shoulders and arms while breastfeeding, which worsens breast tissue drag, which worsens nipple pain

• Result in you accidentally pressuring or coercing your baby to fill up with milk (becaause you're worried about baby's weight), which can cause baby to develop a conditioned dialling up with the breast

• Make it hard for you to expose your baby to adequate sensory motor nourishment, e.g. causing you to spend a lot of time in the low-sensory interior environment of your home, which dials a baby up, which might make you worry that your baby is hungry but "won’t take the breast" or "is breastfeeding all day" even though the problem is actually one of baby's sensory motor needs

• Make it hard for you to relax back into the deck-chair position while breastfeeding

• Make it hard for you to relax into tiny experimental micromovements while breastfeeding.

This is comforting to know, because once you're aware of these possible behaviours, you can alter them, even if you continue to feel stressed inside. You might be managing difficult thoughts and unpleasant stressed or distressed feelings, but what matters for your breastfeeding and for your relationship with your little one overall, is the actions you take and how you behave.

Your nipple still tightens and becomes more prominent when you roll it, no matter how stressed you are. Your stomach still secretes acid to digest the chocolate bar you just ate, no matter how stressed you feel. Your letdown will happen once baby is stimulating the breast. Your milk ejection is a reliable, hardwired neural and hormonal reflex, no matter how stressed you are - even if you don't feel any letdowns at all.

Recommended resources

Does stress affect your breast milk letdowns or supply?

Your milk ejection reflex: what letdown feels like and how it works

Why your milk ejections are resilient and very difficult to disrupt

Busting myths about your letdown or milk ejection reflex

Selected references

Uvnäs Moberg K, Ekström-Bergström A, Buckley S, Massarotti C, Pajalic Z, Luegmair K, Kotlowska A, Lengler L, Olza I, Grylka-Baeschlin S, Leahy-Warren P, Hadjigeorgiu E, Villarmea S, Dencker A. Maternal plasma levels of oxytocin during breastfeeding-A systematic review. PLoS One. 2020 Aug 5;15(8):e0235806. doi: 10.1371/journal.pone.0235806. PMID: 32756565; PMCID: PMC7406087.

Nagel E, Howland M, Pando C. Maternal psychological distress and lactation and breastfeeding outcomes: a narrative review. Clinical Therapeutics. 2023;44(2):215-277.

Prentice A, Paul A, Black A. Cross-cultural differences in lactational performance. In: Hamosh M, Goldman AS, editors. Human Lactation. Boston, MA: Springer; 1986 p. https://doi.org/10.1007/1978-1001-4615-7207-1007_1002.