"By the time your baby is 3 months old and has developed a fairly predictable 24-hour pattern, it becomes more important for you to provide increasingly consistent structure. If you do your best to establish a reasonable and consistent daily routine and keep to it as much as possible, then it is likely that your child will continue to develop good patterns. If instead you allow the times of your child's feedings, playtimes, baths, and other activities to change constantly, chances are his sleep will become irregular as well."
The most well known cry it out technique is the one developed by pediatrician Richard Ferber, director of the Center for Pediatric Sleep Disorders at Children's Hospital Boston. Ferber says that in order to fall asleep on their own and sleep through the night, babies have to learn to soothe themselves. Ferber believes that teaching a baby to soothe himself may involve leaving him alone to cry for prescribed periods of time.
Honestly, in our personalized consultations, we try to avoid this method as much as possible. If you are going to use cry it out, we recommend your baby is at least 6 months old, but preferably 10 months or older, when we expect almost all babies to be able to get through the night without a feeding. It is not for the faint at heart. We find that laying a foundation in the beginning with other strategies and techniques can reduce crying even if this method is used in the end, however.
• Pick-up-put-down method. In this sleep-training method, you put your child to bed while he’s awake and check on him at gradual intervals, as you do with the Ferber method. Unlike with Ferber, you can pick him up and comfort him, holding him for a few minutes before putting him down. Eventually baby will become drowsy enough to fall asleep on his own.
"A young child cannot yet understand what is best for him, and he may cry if he does not get what he wants," Ferber writes. "If he wanted to play with a sharp knife, you would not give it to him no matter how hard he cried, and you would not feel guilty or worry about psychological consequences. Poor sleep patterns are also harmful for your child and it is your job to correct them."
If your baby is older than six months, don’t worry, McGinn says: “It’s never too late to develop good sleep habits.” Dickinson says he finds nine months to be a bit of a sweet spot for parents in terms of getting babies to sleep through the night. “They are at a good age for understanding routines and don’t need to eat during the night,” he explains.