Yesterday, I spent the day in the presence of @Nils Bergman, who is the founder of Kangaroo Mother Care in South Africa. Nils confirmed that swaddling causes high levels of cortisol in infants
and that infants are actually having an extreme stress response which involves shutting down and/or disassociation when they are swaddled. Infants are not "sleeping" when they are swaddled, but are in an extreme biological shutdown which would only happen in case of extreme threat. In other words, if the infant were in the wild and was in extreme danger of being eaten by a wild animal, it would "play dead" and remain very silent so as not to be noticed. Infants are responding the same exact way when they are swaddled and are really in a state of hypervigilance to threat and exhibiting signs of parasympathetic shock.
Swaddling is NOT good. And a better and far more loving way to calm a baby would be to put the baby skin-to-skin with it's mother.
"...In fact, many researchers and infant advocates now believe the apparent contentment of a swaddled baby may in fact be a sign of listlessness and shutting down, rather than of feeling comforted. Franz tells of a new product introduced some years ago at a medical conference. Plugged into a crib, the device vibrated its springs while emitting “white noise.” Fussy babies were believed to be calmed by the rhythmic movement and sounds. But photographs of the babies’ faces told another story.The Question of Routine Swaddling
“In the before photos the eyes were open, hands fisted, there was tightness around the nose and mouth, and the babies were crying,” Franz says. In photos taken as babies experienced the crib device, the hands were still fisted, there was the same furrowed brow and tightness around the eyes and mouth—but the babies were silent. Franz has observed a similar response among swaddled babies. “The baby is staying quiet but is not relaxed or happy. That led me to conclude the baby is shutting down,” she says..."