It’s One of the Most Torturous Parts of Caring for a Baby. But the Biggest Payoff is Very Clear.
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Sleep is a Big Deal to new parents. I'm writing this with a 4-month-old asleep on my chest. She's sleeping well right at this exact moment—but today she woke up every hour from 2 a.m. to 6 a.m., at which point we all had to get up to get ready for the day. And she's not even at the low end of sleeping practices for a baby her age: She sometimes manages to sleep five hours in a row. I would do anything for this tiny creature, but it's not great for her to wake up so much. And at a certain point, you get over the sleep-deprivation feeling of tiny ants biting the inside of your skull.
Sleep is, as the scientists say, physiologically necessary. Without sleep, most of your body starts falling apart. There's even evidence that a baby who refuses to sleep can make you depressed , something that, if you know enough parents or have kids yourself, you might not need a study to tell you.
The question is, how do you get a baby to sleep more? And the answer, weirdly, is that we don't really know. (Even if someone on Instagram claims that they do know the secret … they don't.)
One of the main methods suggested by health authorities to improve sleep in infants is something called sleep training . Sleep training can mean slightly different things to different people, though generally it involves letting the baby cry without rocking or comforting them so that they can, ideally, learn to self-soothe. So, rather than picking up your infant every time they start to scream, you wait a bit, maybe two minutes, before going in and saying something comforting, rather than soothing them back to sleep. Then you extend the wait times. The idea is that, eventually, babies will learn to get themselves back to sleep without the parents intervening and, ultimately, that they get better sleep overall.
This is a highly contentious idea in some parenting circles. Sleep training is basically torture for parents while you are going through the training portion of things, so much so that many loudly claim that sleep training is actively detrimental to babies. (The best evidence we've got, however, does not support any major harms.) But there's nothing like listening to your tiny baby screaming on the other side of the door while waiting for a timer to go off so you can go comfort them. Still, all of the pain might be worth it if sleep training actually works. What does the evidence say?
There's some quite reasonable evidence looking at sleep training over the past three decades. Although some of it is now a bit old— this randomized trial from 2002, for example—the data all looks quite consistent. If we randomize parents to either an intervention in which they are recommended to let their baby engage in controlled crying—usually guidance delivered by a midwife or pediatric nurse—or a control group with no intervention, the parents who use controlled crying report that their children sleep better. For example, a 2007 study randomized 328 mothers to get either the controlled-crying advice or no advice; it showed that the mothers who got the advice reported better sleep three months later and were even less depressed after their children turned 2. And this small 2016 study tested a type of controlled crying called graduated extinction, which also demonstrated significant benefits to parent-reported sleep for those who were given the sleep-training advice compared to those who weren't.
It sounds as if sleep training is highly effective, but there's a problem. As you might have noticed, all of these studies measured parent-reported outcomes. People tend to be biased to think that their hard work has paid off in some way. If you tell people to torture themselves by listening to their baby cry instead of soothing her, there's a reasonable possibility that they will report some benefits to the method even if there aren't any.
There is in fact a study that analyzed whether babies who sleep trained really did get better sleep. A Canadian group randomized families to get either sleep training and infant safety advice or just the safety advice alone. (There is, if you haven't had a baby recently, a lot of safety advice when it comes to infant sleep.) They also asked parents to put an actigraph—a device that monitors movement—on their babies for a week during the assessment period. This allowed the researchers to evaluate not just whether parents thought that sleep training improved sleep, but whether it actually did.
They found that the rate of nighttime wake-ups in both groups, as measured objectively by the actigraphy, was the same. Though sleep training did slightly increase the longest stretch of sleep that infants were able to get, there was otherwise no noticeable improvement in objective sleep caused by the sleep-training advice. (On the flip side, though, sleep training doesn't harm sleep. Your baby will not simply be awake forever if you don't go in and rock them.)
But something interesting showed up in the data as well: Despite the fact that sleep didn't objectively improve, parents in the sleep-training arm reported less depression, less fatigue, better sleep, and better cognition.
This raises an important question: What's the point of sleep training? The Canadian study researchers argued that this shows precisely what they would expect—controlled crying doesn't prevent children from waking up entirely. What it does is reduce the amount of time and effort on the part of the parents that it takes to get the baby back to sleep, and importantly gives the parents a measure of control over their infant's sleep that they didn't have before. If your sleep-trained infant is waking up just as much as they were previously, but you feel as if they're able to get themselves back to sleep—sometimes without waking you up at all—that's huge.
So, yes, to an extent, we can say that this works. Depression and fatigue are, after all, mostly subjective experiences. If parents report better sleep due to controlled crying, then you could argue there is a benefit even if the babies are not, in fact, sleeping any more than they were before.
Importantly, the intervention also reduced one key metric: parental anger about infant sleep. One of the hardest things as a parent whose child is not sleeping is how furious you can get at 4 a.m., even though you know you shouldn't be angry, because they're just a baby. Reducing the feelings of helplessness and even rage that new parents experience is itself a meaningful thing.
Whether or not you pursue sleep training for the imperfect strategy that it is, there's a ray of hope for anyone struggling through the trenches of nighttime wake-ups. In every study, children overall improved dramatically in terms of sleep time by the follow-up. How to get your baby to sleep better tonight might be a bit of a mystery. But every baby, going through sleep training or no, will eventually sleep for a lot longer in the future than they are right now.
