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Babies Are Soothed By Matching Heartbeats With Their Mother

Mothers with postpartum depression have a harder time soothing their babies. Now we know why - and what to do about it.


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

A mother holding a sleeping bubba
Babies get soothed by their mothers' heartbeat - unless their mothers have untreated depression.
Image Credit: Alena Ozerova/Shutterstock

A lot of trivia can be organized according to the noise you make when you learn it. There are your “ahh!” facts, like how infinities can be different sizes; then there are the “wah?” facts, like how sharks existed before the rings of Saturn; there are even “eww!” facts, like your dog’s, uhm, grieving process

Best of all, there are the “aww!” facts – like the one recently elucidated in the Journal of Psychopathology and Clinical Science. In a study investigating why some mothers seem to have a unique ability to calm their upset babies, researchers discovered something quite adorable: it all comes down to synchronized heartbeats. 


“This study demonstrates empirically, for the first time, that synchronized physiology between mothers and babies plays a role in soothing distressed infants,” said study lead John Krzeczkowski, postdoctoral fellow in the Department of Psychology at York University, in Canada, in a statement.

“[It has] provided important clues into how soothing signals may be transmitted in real time on a moment-to-moment scale between mothers and infants.”

That’s not the only important discovery they made. It turns out that for new mothers with post-partum depression (PPD), this effect doesn’t work the same way – and the researchers were able to figure out why.

“Many studies have shown that mothers with postpartum depression struggle to calm their distressed babies,” Krzeczkowski noted. “However, it is not known how mothers’ soothing signals are transmitted to their baby, how postpartum depression disrupts this process, or if treating depressed mothers can alter these signals.”


To investigate, the team worked with two sets of mother-infant pairs: the control set consisted of mothers without PPD, and the other comprised mothers who had received a diagnosis within a year of giving birth. 

All pairs were observed throughout three phases of interaction. First, there was the play phase, in which mothers played with their babies as they would normally. Next came a “still-face” phase, which was exactly what it sounds like: the mothers were directed to show no emotion, to not touch or speak to the babies, and to maintain eye contact only.

Unsurprisingly, this made the babies quite upset – but that was the point. The third phase of the experiment was a reunion phase, where mothers were allowed to interact with their babies as normal once again.

Researchers were also monitoring both the mothers’ and babies’ heart rates. That told them how much emotional distress was being felt by the participants: the more variation in the heart rate, the more stressed out the babies and their mothers were.


That’s when the team saw it: “Among healthy dyads, maternal [heart-rate variability] influenced subsequent decreases in infant [heart-rate variability],” explains the paper – an effect Krzeczkowski refers to as the “soothing dance.” 

However, in mothers with PPD, the opposite was true: the heart rates still synched up, but it was the mothers’ who followed their babies’ physiology. Was this how PPD can stop mothers from soothing their infants?

To find out, the researchers gave the group a course of cognitive behavioral therapy (CBT) – a type of talking therapy that concentrates on consciously modifying thoughts and behavior to help with certain mental and physical health problems. If PPD was the cause of this reversal, could therapy counteract the effect?

The answer? Happily, yes: “treating PPD with CBT can improve the synchrony patterns and thereby augment mothers’ ability to soothe their distressed babies,” explained Krzeczkowski.


There’s one caveat, however: as it stands, the link is only correlation. But the team hopes that, with future research, a causal link can be established, bringing hope to the roughly one in five mothers who experience postpartum depression.

“Because of our study’s observational design, we can’t say conclusively that positive changes were specifically due to CBT treatment,” Krzeczkowski said. “However, it may be contributing, and we now need to replicate this finding and understand how it works."

“Our goal is to ensure that more people can get treatment for PPD when they need it. We hope that by conducting future studies that can show causality, it can increase the idea that these programs can benefit them,” he concluded.


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  • tag
  • psychology,

  • mental illness,

  • health,

  • babies,

  • therapy,

  • heart rate,

  • postpartum depression