Yes. Multiple studies have shown that sleep training is both safe and effective, without any studies showing evidence of harm. The best long-term study followed 326 children for the first six years of life. The authors reported that children who had sleep trained via any method in infancy slept better at 2 years of age than children who were not sleep trained, and their mothers were less likely to be depressed. Several years later, the researchers looked at these children again and noted that there was no evidence of emotional or behavioral problems in children who had been sleep trained versus those who had not. As part of this follow-up, the researchers measured the children’s levels of the stress hormone cortisol, which is frequently cited by opponents of sleep training as the mechanism by which crying affects developing brains. The researchers did not find any evidence of differing levels of cortisol secretion between children who had been sleep trained and those who had not.
"My 4-and-a-half-month-old will only sleep through the night if we do everything the experts say not to do. She must be nursed to sleep unless we want to see her turn purple and cry for 45 minutes or more. She's like a wind-up doll when she starts and never settles until she's comforted, and she's been that way from the beginning. It really became a matter of, "Do we want to sleep, or do we want to do what the books say?" If she's comforted and put down sleeping, she sleeps eight to 10 hours. To all you parents out there who have a baby like mine, do not despair – just do what works for you."
Most experts recommend starting when your baby is between 4 and 6 months old. By about 4 months, babies have typically started to develop a regular sleep-wake cycle and dropped most of their night feedings. These are signs they may be ready to start sleep training. Many babies this age are also developmentally able to sleep for long stretches at night.
"I have a 5 1/2-month-old baby girl who has never once in her life "cried it out." From night one in the hospital, she has slept with me. She is rocked and nursed to sleep and when she starts to grunt/wiggle beside me, I simply shift near enough for her to latch on to my breast, and she nurses back to a deep sleep before either of us fully wakes. I follow Dr. Sears' attachment style parenting and my baby has never once in all her life cried during the night or even fully woken up."
“I knew I didn’t want to sleep train, so I co-slept with my son until he was about 5 months old,” says Corinna, a mom of two. “At 5 months, I was able to put him in a room on his own, but I would attend to him if he cried. By 10 months, he was sleeping through the night on his own. Maybe I was lucky, but I felt like what worked best for our family was following his lead.”
The age of your baby might determine what kind of sleep-training method you choose, though. You could try a gentle shush-pat technique with a five-month-old, but you’ll likely have to leave a one-year-old in the crib as they protest (cry or scream) about the new bedtime arrangement. Don’t attempt a formal sleep-training method before four months, until your baby is able to go longer in between feeds and their circadian rhythm starts to develop. (Many babies this age still feed in the night—contrary to popular thinking, sleep training isn’t synonymous with night weaning.) Dickinson says that many four-month-old babies are biologically able to go through the night without a feed, but that doesn’t mean you shouldn’t respond and feed them if other methods of calming them aren’t working. Since every situation is different, we recommend checking with your doctor before withholding your baby’s night-time feeds.