At what age is sleep training safe and does it work?

What the evidence says

Most experts say it's reasonable to start sleep training around 4 to 6 months, once babies have more regular sleep cycles and typically no longer need night feeds. An expert-reviewed source notes that a good idea is to get the go ahead from your pediatrician to make sure your baby's weight is on track and they are getting enough calories during the day before starting.

On whether it works: research says yes. A psychology summary of the evidence states that sleep training is highly effective, though it can be controversial because parents worry about potential negative consequences of prolonged crying.

On safety: this is the part parents worry about most, and the best evidence is reassuring. Two randomized controlled trials found no significant differences in emotional or behavioral problems or attachment styles either one year or five years following a sleep training intervention. An expert summarized it simply: the evidence suggests that sleep training is safe, but ultimately it's the family's decision.

That said, not every method has to involve letting a baby cry alone for long stretches. Gentler approaches exist, and if a family isn't comfortable with a particular method, waiting things out or trying a gentler approach are also reasonable options, according to the same expert.