Letting a baby cry it out is generally considered safe for healthy infants who are at least 4 months old and weigh around 14 pounds. Multiple studies have found no lasting harm to the baby’s emotional development or parent-child bond, and the method can significantly improve sleep for the entire family. That said, it’s not appropriate for every baby or every age, and there are important details worth understanding before you try it.
What “Cry It Out” Actually Means
The phrase “cry it out” gets used loosely, but it refers to a specific category of sleep training called extinction. You put your baby down drowsy but awake, leave the room, and don’t return until morning (or until a scheduled feeding). The goal is for the baby to learn to fall asleep without being rocked, fed, or held. It sounds harsh in description, and it feels harder than it sounds in practice, but the crying typically decreases sharply within a few nights.
A more popular variation is graduated extinction, often called the Ferber method after the pediatrician who popularized it. Instead of no check-ins at all, you return to briefly reassure your baby at increasing intervals. You might wait 3 minutes before the first check-in, then 5 minutes, then 10. When you go back in, you keep it short (under two minutes), pat their back or speak softly, but don’t pick them up or feed them. Over several nights, the intervals stretch longer and the crying tapers off. Many parents find this version more tolerable emotionally while still being effective.
Why 4 Months Is the Earliest Starting Point
Newborns should never be left to cry it out. Before about 3 months, babies haven’t developed their own melatonin production or the ability to regulate sleep cycles. They can’t distinguish day from night reliably, and they genuinely need to eat every few hours. Their short sleep cycles and small stomachs make sleeping through the night biologically impossible.
Around 4 months, several things change at once. The baby’s circadian rhythm starts functioning, sleep cycles begin to mature, and many babies no longer require nighttime feedings. This is also when babies become developmentally capable of learning to self-soothe. The weight threshold matters too: a baby who weighs at least 14 pounds can typically go longer stretches without needing calories overnight. Your pediatrician can confirm whether your specific baby is ready, especially if they were premature or have any health concerns that might mean they still need those nighttime feeds.
What the Research Shows About Safety
The biggest worry most parents have is that letting a baby cry will cause emotional damage, weaken attachment, or flood the baby with harmful stress hormones. The evidence doesn’t support those fears. A study of 43 babies published in Pediatrics in 2016 measured cortisol (the body’s primary stress hormone) in babies who learned to self-soothe through sleep training. One year later, those babies showed no greater signs of attachment problems or emotional issues compared to a control group. Their cortisol levels were actually lower than those of babies in the control group whose caregivers received no sleep training guidance.
This finding is important because cortisol is what critics of cry it out most often point to. The concern is that prolonged crying spikes stress hormones in ways that could affect brain development. But the data consistently shows that the stress of a few nights of sleep training doesn’t translate into measurable harm. What does cause measurable harm is chronic sleep deprivation, both for babies and parents.
The Effect on Parents’ Mental Health
Sleep deprivation in new parents isn’t just unpleasant. It’s a significant risk factor for postpartum depression, anxiety, and relationship strain. A study published in BMJ Open tracked mothers whose babies were waking an average of 5 times per night. After a sleep intervention, those wakings dropped to an average of 0.5 per night. The change in the mothers’ mental health was striking.
Before the intervention, 32.5% of the mothers met criteria for depression. Afterward, that number fell to 5%. Anxiety dropped from 25% to 15%. Stress went from affecting nearly half the mothers (48.8%) down to 20%. Depression scores specifically showed a 66% reduction. These aren’t small improvements. For many families, sleep training doesn’t just fix a baby’s sleep; it pulls a parent out of a mental health crisis.
When Cry It Out Isn’t the Right Fit
Not every baby is a candidate for sleep training. Babies under 4 months, babies who are underweight, and babies with medical conditions that require overnight feeding should not be left to cry. If your baby is sick, teething badly, or going through a major transition like starting daycare, it’s worth waiting until things stabilize. The method works best when the baby is healthy, well-fed, and in a consistent sleep environment.
It’s also worth acknowledging that some parents simply can’t do it. Listening to your baby cry for extended periods triggers a deep biological response, and for some parents the distress outweighs the benefit. That’s a valid reason to choose a gentler approach. Graduated methods like the Ferber technique offer a middle ground, and there are even more gradual options (like sitting in the room and slowly moving your chair toward the door over several nights) that involve less crying overall, though they tend to take longer.
How to Make It Work
If you decide to try cry it out, consistency is what separates success from a miserable experience that doesn’t actually improve anything. Going in and picking up your baby after 45 minutes of crying teaches them that 45 minutes of crying gets results, which makes the next night worse, not better. Whatever approach you choose, commit to it for at least a week before evaluating.
A few practical things that help: establish a short, predictable bedtime routine (bath, book, song, bed) so your baby gets clear signals that sleep is coming. Put them down drowsy but not fully asleep, since falling asleep independently is the whole skill you’re trying to build. Keep the room dark and use white noise if it helps. And start with bedtime, not naps. Bedtime is when sleep pressure is highest, so it’s the easiest win.
Most families see significant improvement within 3 to 5 nights, though some babies take a full week. The first night is almost always the hardest, with crying that can last 30 to 60 minutes or more. By the third or fourth night, many babies fuss for under 10 minutes before falling asleep. The pattern holds for both full extinction and graduated methods, though graduated approaches sometimes take a night or two longer.