Babies who are deliberately left to cry themselves to sleep are more stressed than babies who are comforted to sleep — that’s according to a new study published in the journal Early Human Development.
Even though these babies would eventually settle themselves, researchers found that hormone levels showed that they remained just as stressed by the experience, as if they had remained crying.
This method of sleep training – often used by parents — is thought to help babies self sooth and learn to fall asleep.
The study, which was conducted by Wendy Middlemiss, researcher at the University of North Texas analysed the effects of the experience on children and their moms.
The babies who were observed were between the ages of 4 and 10 months. Researchers monitored their levels of cortisol and measured the length of time they cried over successive nights – while their moms listened in a nearby room.
Researchers observed that infants cried for a shorter period on the third night, before falling asleep. However their stress levels were elevated.
In mothers, who could hear their babies, the level of the hormone fell in accordance with the time spent crying, indicating they had relaxed as the youngsters appeared to settle.
“Although the infants exhibited no behavioural cue that they were experiencing distress at the transition to sleep, they continued to experience high levels of physiological distress, as reflected in their cortisol scores, Wendy Middlemiss said.
She added that “given the continued presence of distress, infants were not learning how to internally manage their experiences of stress and discomfort.”
Researchers are now undertaking a longer study to test how the hormone level is affected as sleep patterns settle over more time.