The Bottom Line “Cry it out” methods are effective at encouraging nighttime sleep. There is evidence that using these methods improves outcomes for parents, including less depression and better general mental health. There is no evidence of long- or short-term harm to infants; if anything, there may be some evidence of short-term benefits. There is

And we did sleep train Penelope, working roughly out of the Healthy Sleep Habits, Happy Child playbook.

Generally, it will be easier to sleep train a six-month-old than a three-month-old, and probably harder to train a two-year-old. But these methods seem to work on a variety of ages.

Which Method, and When? Most “cry it out” methods are variants on one of three themes: Extinction—just leave, and do not return; Graduated Extinction—come back at increasingly lengthy intervals; and Extinction with Parental Presence—sit in the room, but do not do anything. Ferber is a proponent of the second, whereas Weissbluth is more in favor of

We can say, for example, that one year of parental leave versus two years doesn’t influence a child’s high school test scores or earnings in early adulthood.

The Bottom Line There are some broad guidelines for a sleep schedule. Longer nighttime sleep develops around two months. Move to three regular naps around four months. Move to two regular naps around nine months. Move to one regular nap around fifteen to eighteen months. Drop napping around age three. There is tremendous variability across children

The Bottom Line There is good evidence that infants who sleep on their back are at lower risk for SIDS. There is moderate evidence that bed sharing is risky. These risks are much higher if you or your partner smokes or drinks alcohol. There is some less-good evidence that room sharing is beneficial. The benefits to room sharing die out in the first

The vast majority—up to 90 percent—of SIDS deaths occur in the first four months of life, so sleeping choices after four months are very unlikely to matter for SIDS. This also shows up in the data. The choice of sharing a room, or even sharing a bed, does not seem to affect SIDS risk after three or four months, at least for parents who are nonsmoke

Notably, there does not seem to be any elevated risk from co-sleeping after three months if both parents are not drinking or smoking.