From Oster again: "I think it is fair to say that it would be good to have more data—it’s always good to have more data! And yes, it is possible that if we had more data, we would find some small negative effects. The studies we have are not perfect.
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. There isn’t anything in the data that shows this, but there is similarly nothing to show that sleep training is bad.
You could also argue that the effects of maternal depression on children are long-lasting, and therefore this intervention may have beneficial long-term effects. This seems in many ways more plausible. You’ll have to make a choice about this without perfect data. (This is true of virtually all parenting choices. Blame the parenting researchers!) But it would be a mistake to say, for example, that not sleep training is the “safest option.”
Does all this mean you should definitely sleep train? Of course not—every family is different, and you may really not want to let your baby “cry it out.” You need to make your own choices, just as with everything else. But if you do want sleep train, you should not feel shame or discomfort about that decision. The data, imperfect as it is, is on your side."
Oster, Emily. Cribsheet (pp. 181-182). Profile. Kindle Edition.