They returned to evaluate the children a year later and five years later, when the children were 6. In this later follow-up, which included a subset of the original families, the researchers found no difference in any outcomes, including emotional stability and conduct behavior, stress, parent-child closeness, conflict or parent-child attachment. Basically, the kids who were sleep-trained looked exactly like those who were not.
These results are not an outlier. Review studies of sleep-training interventions do not find negative effects on infants. And many show sizable improvements in maternal depression and family functioning. Sleep affects mood, and parents who sleep less feel worse. The evidence paints a pretty pro-“cry it out” picture.
Nonetheless there are academic articles that argue against it. One small study that gets a lot of play shows that in the few days after sleep training, mothers are less stressed, but the same is not true of infants. The researchers interpret this as a signal that the mothers and children are losing emotional touch with each other, but this is a stretch. Why not interpret the evidence to say that cry-it-out relaxes parents without hurting children?
Fundamentally, the argument against sleep training is theoretical: that some children are devastated, even if those results don’t show up in the data, or that the damage may not manifest until babies are adults.
I think it is fair to say that it would be good to have more data. It’s always good to have more data! However, the idea that this uncertainty should lead us to avoid sleep training is flawed. Among other things, you could easily argue the opposite: Maybe sleep training is very good for some kids — they really need the uninterrupted sleep — and there is a risk of damaging your child by not sleep training.
Does this mean you should definitely sleep train? Of course not — every family is different, and you may not want to let your baby cry. But if you do want to sleep train, you should not feel shame or discomfort about that decision.
Finally, there are some parenting decisions where the data just isn’t much help at all, and family preferences have to take the front seat. One example is the question of whether to work outside the home.