Letting a baby cry it out is not harmful when done at the right age and in a structured way. Multiple studies have followed children who went through cry-it-out sleep training and found no lasting differences in emotional development, behavior, or the parent-child bond compared to children who were never sleep trained. That said, timing and method matter, and understanding the nuances will help you feel confident in whatever approach you choose.
What “Cry It Out” Actually Means
The phrase “cry it out” gets used loosely, but it refers to a spectrum of sleep training techniques. At one end is unmodified extinction, where you put your baby down awake, leave the room, and don’t return until morning (outside of genuine needs like hunger or illness). At the other end is graduated extinction, commonly known as the Ferber method, where you leave the room but return at set intervals to briefly comfort your baby without picking them up. You might check in after three minutes, then five, then ten, with the gaps growing longer each night.
Both approaches share the same core idea: giving your baby the opportunity to learn how to fall asleep without being rocked, fed, or held. The difference is how much parental reassurance happens along the way. Most families who say they “tried cry it out” are actually using some version of graduated extinction, not leaving their baby to cry indefinitely with no response at all.
What the Research Shows About Safety
The largest and most frequently cited study on this topic, published in Pediatrics in 2012, followed 225 children for five years after their families were randomly assigned to either a sleep training group or a control group. At age six, researchers found no measurable differences between the two groups in emotional health, behavior, sleep quality, stress levels, or the quality of the child-parent relationship. Cortisol levels (a biological marker of stress) were also equivalent.
A 2016 trial published in Pediatrics compared graduated extinction, a technique called “bedtime fading,” and a control group. After three months, babies in both sleep training groups fell asleep faster and woke less often. Cortisol samples taken the morning after sleep training showed no elevation compared to the control group. Parent-child attachment was also unaffected.
These findings don’t mean crying is pleasant or that it feels easy to listen to. They mean that brief periods of crying during a structured sleep learning process do not appear to cause measurable harm to babies who are developmentally ready for it.
Why Age Matters
Newborns cannot self-soothe. They lack the neurological capacity to regulate their emotions, which is why they depend entirely on a caregiver to calm them. The Cleveland Clinic advises against any self-soothing practice before three months of age, and the American Academy of Pediatrics frames sleep training guidance around babies four months and older.
Around four to six months, most babies have developed enough neurologically to begin learning independent sleep skills. They can recognize familiar surroundings, start to anticipate routines, and their sleep architecture has matured enough that they cycle through lighter and deeper sleep more like an adult. This is the window when sleep training becomes both safe and more likely to work. The AAP notes that by six months, it’s normal for babies to wake during the night and put themselves back to sleep within a few minutes without intervention.
Emotional self-regulation is a process that takes years to develop fully, so no one is expecting an infant to manage complex emotions. Sleep training targets one narrow skill: falling asleep without external help. It’s not asking a baby to suppress distress or cope with abandonment.
The Effect on Parents
One dimension that often gets overlooked in the cry-it-out debate is what happens to parents, particularly mothers, when no one in the household is sleeping. A study published in BMJ Open tracked 80 mothers through a sleep intervention and found striking improvements. Before the intervention, 32.5% of mothers scored in the depressed range on a validated mental health scale. Afterward, that number dropped to 5%. Anxiety fell from 25% to 15%, and stress from 48.8% to 20%.
The babies’ nighttime awakenings dropped from an average of five per night to 0.5, and the researchers found a direct statistical correlation between how often babies woke and how stressed and depressed their mothers felt. This isn’t surprising, but it’s worth stating plainly: chronic sleep deprivation is a significant risk factor for postpartum depression, and postpartum depression affects the baby too. A well-rested parent is more emotionally available, more patient, and better equipped to provide responsive care during waking hours.
When Cry It Out May Not Be the Right Fit
Sleep training works well for many families, but it isn’t the only path and it isn’t always appropriate. Babies younger than four months, premature infants (adjusted for their corrected age), and babies with medical conditions that cause pain or discomfort at night need a different approach. If your baby is hungry, sick, or going through a major transition like starting daycare, it’s worth waiting until things stabilize before introducing any new sleep routine.
Some parents find that any amount of crying feels deeply wrong to them, and that’s a legitimate response. Attachment-focused alternatives exist, including chair methods (where you sit nearby and gradually move farther away over days) and pick-up-put-down techniques. These tend to take longer but still help babies learn independent sleep. The “best” method is the one you can follow through on consistently, because inconsistency, starting cry it out and then abandoning it after 45 minutes, tends to make things worse by teaching a baby that prolonged crying eventually gets results.
How to Make It Work
If you decide to try a cry-it-out approach, a few practical details make a big difference. Start with a consistent bedtime routine: a bath, a feeding, a book, a song, whatever signals to your baby that sleep is coming. Put them down drowsy but still awake, which is the single most repeated piece of advice from both the AAP and sleep researchers. The goal is for the last thing your baby remembers before falling asleep to be their crib, not your arms.
Expect the first two or three nights to be the hardest. Most babies cry for 30 to 60 minutes the first night, with significant improvement by night three and the process largely complete within a week. If you’re using the Ferber method, keep your check-ins brief and calm. You can talk softly or shush, but avoid picking your baby up or turning on lights. The purpose of the check-in is to reassure your baby (and yourself) that you’re still there, not to restart the soothing process from scratch.
Track your baby’s progress rather than watching the clock in the moment. Parents who log how long the crying lasted each night almost always see a clear downward trend, which helps counteract the in-the-moment feeling that things aren’t improving.