Letting a baby cry it out is not harmful when done at the right age and in the right way. Multiple large studies have found no lasting negative effects on a child’s emotional development, stress levels, or attachment to their parents. That said, the details matter: how old your baby is, which approach you use, and what “cry it out” actually means in practice can look very different from family to family.
What “Cry It Out” Actually Means
Most parents who say “cry it out” are really talking about one of two approaches, and the difference between them is significant.
Graduated extinction (the Ferber method) is the most common version. You put your baby down drowsy but awake, leave the room, and wait a set number of minutes before going back to briefly comfort them. You don’t pick them up, but you can shush, pat, or talk quietly. Then you leave again, and the interval before your next check gets a little longer each time. Over several nights, the intervals stretch out and the crying typically shrinks. Cleveland Clinic describes it as “essentially the cry-it-out method but with check-ins.”
Unmodified extinction is the more intense version. You put the baby down, say goodnight, and don’t return until morning (or the next scheduled feeding). There are no check-ins. This approach tends to work faster but is emotionally harder for parents to sustain.
Both methods aim to teach the same skill: falling asleep without a parent’s physical presence. The goal isn’t to ignore your baby’s needs. It’s to give them the chance to learn self-soothing, which is a developmental ability that emerges around 4 to 6 months of age.
What the Research Says About Safety
The biggest concern parents have is whether prolonged crying causes psychological harm, elevated stress hormones, or damage to the parent-child bond. Researchers have looked at this directly.
A landmark 2016 study published in Pediatrics randomly assigned 43 infants to graduated extinction, a gentle bedtime-fading technique, or a control group. The researchers measured cortisol (the body’s primary stress hormone) in the babies’ saliva and followed the families for a year. Babies in the graduated extinction group fell asleep faster and woke less often, and their cortisol levels were no different from babies in the other groups. At the 12-month follow-up, there were no differences in emotional or behavioral problems, and no differences in parent-child attachment security.
A larger Australian trial followed over 200 families for five years after sleep training. At age six, children whose parents had used controlled crying showed no measurable differences in emotional health, behavior, sleep quality, stress regulation, or closeness with their parents compared to children who were never sleep trained. The results held regardless of which method parents had used.
No well-designed study has found evidence that cry-it-out methods cause lasting harm. The fear that a baby left to cry will develop attachment issues or chronic stress is not supported by the data.
When Babies Are Ready
Age matters. Sleep training of any kind is generally appropriate starting at 4 months, when babies begin developing the neurological ability to self-soothe and their sleep cycles start consolidating into longer stretches. Before that point, frequent waking is biologically normal and often tied to feeding needs.
The American Academy of Pediatrics advises putting babies 4 months and older down when they are drowsy rather than fully asleep, and recommends not rushing in to soothe a crying baby because “babies need time to put themselves back to sleep, and they need to learn how to fall back asleep on their own.” They note that parents should still attend to genuine needs like hunger, a dirty diaper, or illness.
Premature babies may not be ready at the same calendar age as full-term babies. If your baby was born early, their adjusted age (counted from their due date, not their birth date) is the better guide.
What the First Week Looks Like
If you’re considering cry it out, knowing the typical timeline helps set realistic expectations. The first night is hard, but it’s usually not the hardest.
Many babies experience what’s called an “extinction burst” on the second or third night. This is a temporary spike in crying, where the baby protests more intensely than the first night because the old routine (being rocked, fed, or held to sleep) isn’t working anymore and they haven’t yet learned the new one. It can feel like things are getting worse, but it’s actually a predictable part of the process and a sign that learning is happening.
After that peak, crying typically drops off. Most babies show clear improvement by the end of the first week. By two weeks, the crying is usually done. If you don’t see meaningful progress within that window, it may be worth pausing and reassessing with your pediatrician. Some babies have underlying issues like reflux, ear infections, or sleep apnea that make self-settling genuinely difficult.
Why Some Babies Struggle More
Temperament plays a real role. Babies who are naturally more intense, more persistent, or slower to adapt to change tend to cry longer and louder during sleep training. This doesn’t mean the method isn’t working or that you’re doing something wrong. It means your baby’s personality makes transitions harder, which is information about who they are, not a sign of distress that requires intervention.
Consistency is the single biggest factor in whether sleep training succeeds. Responding to crying intermittently, sometimes going in and sometimes not, actually teaches a baby to cry harder and longer because the unpredictability keeps them guessing. If you decide to try a cry-it-out approach, committing to the plan for at least a full week gives the clearest picture of whether it’s working.
What Cry It Out Doesn’t Mean
Letting a baby cry it out does not mean ignoring them around the clock. It applies to sleep transitions: bedtime and middle-of-the-night wakings where the baby is fed, dry, and safe. During the day, responsive parenting remains exactly the same. You still pick them up when they’re upset, comfort them when they’re scared, and meet their needs consistently. Sleep training is a narrow intervention, not a parenting philosophy.
It also doesn’t mean skipping nighttime feedings before a baby is ready. Many 4- to 6-month-olds still need one or two overnight feeds. You can sleep train while keeping those feeds. The goal is teaching the baby to fall asleep independently, not to go 12 hours without eating before they’re developmentally able to.
Some families try cry it out and find it’s not for them. That’s a valid choice. Gentler methods like bedtime fading (gradually shifting the bedtime later until the baby falls asleep quickly) or chair methods (sitting near the crib and slowly moving farther away over days) also work. They tend to take longer but involve less crying. The research suggests all behavioral sleep interventions produce similar outcomes in the long run. The “best” method is the one you can follow through on consistently.