Using behavioural training to help babies fall asleep doesn't seem to harm them emotionally or developmentally years later, but it also doesn't benefit them long-term either, according to an Australian study.
The study, which appeared in the journal Pediatrics, followed on a 2007 study by the same researchers that found babies and their parents benefited when the infants were taught to settle themselves to sleep with behavioural techniques.
But parents and doctors have expressed concern that the techniques could harm the children's emotional development, and thus their later mental health and ability to handle stress.
There were also concerns over whether the techniques would have an impact on the children's relationship with their parents.
"We wanted to find out if the benefits were really long lasting and if there were any long term effects," said lead author Anna Price, from The Royal Children's Hospital in Victoria, Australia.
Price and her colleagues followed the same children and parents they had followed for the 2007 study.
In the original study, 326 children who had trouble sleeping were randomly assigned to different groups for their parents to try various sleep-encouraging techniques with the help of nurses.
At the end of the study, researchers found the use of certain methods, such as "controlled comforting" and "camping out," improved the children's sleep problems and helped mothers with depression.
Controlled comforting is when a mother periodically responds to her child's cries, instead of the much-discussed "cry it out"approach. Camping out is when parents slowly ease out of a child's room, which eventually teaches the baby to sleep without a parent there.
For the new study, researchers were able to follow up with 225 of the children from the original study. Of those, 122 had gone through the sleep training while the other 103 had not.
Overall, 9 per cent of the 6-year-olds who went through training were having sleep problems compared with 7 per cent of those who did not go through training - a difference so small that statistically, it could be due to chance.
The researchers also didn't find any differences when it came to the children's emotions, conduct or stress.
Among parents, the researchers didn't see a difference between those who had tried training their infants and those who did not when it came to rates of depression, anxiety and stress.
Moreover, there didn't seem to be any difference between the two groups in the degree of closeness between children and their parents.