Using behavioral training to help babies fall asleep doesn't seem to harm them emotionally or developmentally years later, but it doesn't benefit them long-term either, according to a new study.

Australian researchers, who published their findings in the journal Pediatrics on Monday, found that of 225 six-year-olds, those who participated in sleep training when they were babies were no different in terms of emotional health from those who did not.

The study is a follow-up to some of the researchers' earlier work - originally published in 2007 - that found babies and their parents benefited when the infants were taught to settle themselves through various behavioral techniques.

Parents and doctors, however, 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 impact the children's relationships with their parents.

"We wanted to find out if the benefits were really long lasting and if there were any long term effects," said Anna Price, the study's lead author from The Royal Children's Hospital in Victoria, Australia.

Price and her colleagues turned to the same children and parents they followed for the 2007 study to answer those questions.

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 parent periodically responds to their child's cries - instead of the frowned upon approach of letting the child "cry it out." Camping out, on the other hand, 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, the 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, nine percent of the six year olds who went through training were having sleep problems compared to seven percent 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.

Dr. Umakanth Khatwa, the sleep lab director at Boston Children's Hospital in Massachusetts, called the new study "excellent work."

"I think they looked at this from all sides, and we needed this kind of long term study," Khatwa, who was not involved in the new research, said in an interview.

Price told Reuters Health that the new results show the techniques are safe for children older than six months old. And, regarding possible harm, "the research that's out there answers the questions quite conclusively."