The book, Sleep, Child, by Sylvia de Béjar and Eduard Estivill, promotes a version of the method in which parents refuse to comfort or breastfeed infants after bedtime, after which it claims the infants learn to “self-soothe”.
In June, Gyldendal put out a press release announcing its intention to keep selling the book in the face of a Facebook campaign last summer, saying it had contacted international experts. “The response from researchers, both national and international, has not led to a change in the publishers position on keeping the book on the shelves,” it said.
But the 723 psychologists, led by the Copenhagen-based researcher Christine Posselt, in their letter questioned which researchers the company had contacted, insisting that there was evidence that the method risked causing long-term emotional damage.
“Babies and toddlers rely heavily on the comfort and care of their parents, and it can have negative consequences for their development if they are not comforted and reassured when they are upset,” the psychologists wrote.
“Children who have not been met with enough care when they were upset may find it more difficult to deal with their emotions, among other things. In addition, a lack of comforting and care can damage the connection between the child and the parents.”
After the letter, Danish media contacted parents who had used the controversial method.
Niels Groth, a teacher in Copenhagen, used the method on his son Uffe when he was seven months old, and watched the time his son spent crying decreaase from 50 minutes on the first night to sleeping straight away on the fourth.
“He cried much less than I had feared, and was less upset,” he told Danish state broadcaster DR.
The psychologists attacked de Béjar and Eduard Estivill's characterisation of infant crying as “manipulative”, and also their assertion that if a child is suffering from a sleep disorder if he or she still wakes up in the middle of the night at six months old.
“If the child cries so violently that it vomits, even this is seen as a way to get the parents' attention, and the parents are encouraged to simply change the bedding and then let the child cry further,” the psychologists wrote.
“We would like to emphasize that crying is not a form of manipulation and that babies and toddlers are not at all able to manipulate, nor to vomit on purpose.”
They also criticised an idea that when the child stops crying it has learned to 'self-soothe'.
“It is known from the research that babies and young children are not able to soothe themselves at all,” they wrote. “The child has simply become quiet because it has learned that its crying is ignored. In other words, the child may still be sad, scared and lonely, but it has stopped expressing his feelings.”