Infants left to cry themselves to sleep will not suffer any emotional, behavioral or parental attachment problems, a new study suggests. The findings may help parents rest easier knowing that ignoring their babies’ cries won’t cause long-term damage.

Australian researchers found babies allowed to CIO — "cry it out" or cry themselves to sleep, a method called "graduated extinction" by researchers, did not produce any more signs of stress in the infants than a “gentler” method, according to the study published Tuesday in the journal Pediatrics.

“Both treatments helped the babies fall asleep quicker,” said the study’s lead author, Michael Gradisar, an associate professor and clinical psychologist at Flinders University in Adelaide, Australia. “However graduated extinction was better in reducing the number of times the infants woke during the night, as well as the amount of time they spent awake during the night.”

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Gradisar and his colleagues randomly assigned 43 sets of infants and parents to one of three groups: graduated extinction, "bedtime fading," or a control group in which parents just received information about infants and sleep. In the bedtime fading group, infants were put to bed a little later each night in the hopes that the children would drop off quicker if they were more tired.

The researchers kept track of when the babies were sleeping during the night with an ankle monitor and also measured a stress hormone, called cortisol, in the babies’ saliva the next day.

The sleep method made little difference between the infants in terms of stress hormone levels. But those who were in the "cry it out" group went to sleep faster and slept more soundly during the night than those in the other two groups. Infants in the CIO group slept around 20 minutes more during the night, on average, compared to the babies in the "bedtime fading" group.

Babies in the control group, whose parents just got general information about sleep, took the longest to drop off and slept the least amount during the night.

The advantage of CIO, Gradisar said, is that parents and babies are less likely to fall into what researchers call “a coercive behavior trap,” meaning that babies are more rewarded by their parents’ responses to their cries than they are by falling back to sleep.

“This is especially true if the parent responds quickly after the child cried,” he said. “The result being the child is more likely to cry more often thus disrupting the sleep of both themselves and their parents.”

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The new study adds to the body of research showing that children sleep better when parents adopt the extinction method, said Dr. Marc Weissbluth, a professor of clinical pediatrics, emeritus, at Northwestern University’s Feinberg School of Medicine and author of “Healthy Sleep Habits, Happy Child, 4th Edition: A Step-by-Step Program for a Good Night's Sleep.”

“This study shows there is no harm in letting children cry to help them sleep better,” said Weissbluth, a longtime proponent of cry-it-out methods who was not involved in the study. “They are not stressed more.”