Research

Does sleep training have long-term effects?

What the longest sleep training follow-up found at age 6, what shorter studies add, and what the research still cannot tell you.

The Ferber team September 28, 2026 6 min read

Here is what usually happens, with a research note citing Price et al., Pediatrics, 2012.

Most worries about sleep training are about the long run. Will my baby trust me less? Will this show up years later? It is a reasonable thing to want to know before you start, and it is the question that comes up most in arguments about the Ferber method.

Here is what the best evidence says. The longest randomized follow-up tracked children from an Australian infant sleep trial until they were 6. Children’s outcomes at age 6 were no different whether or not families had sleep trained. That included emotional and behavioral problems, sleep, stress and closeness to their parents. Parents’ mental health was no different either. The authors concluded that behavioral sleep techniques have no marked long-lasting effects, positive or negative.

The study that followed children to age 6

The study most often cited on this question is Price and colleagues’ 2012 paper in Pediatrics (Price et al., 2012). It is worth understanding in some detail, because it is both the strongest evidence available and easy to misquote.

Who was in it. Researchers recruited a population sample of 692 infants from well-child centers in Melbourne, Australia. Of these, 326 children whose parents reported a sleep problem at 7 months were included in the trial, 173 of them in the intervention group.

What families got. The trial was cluster-randomized, meaning whole well-child centers were assigned to one group or the other. Families in the intervention group were taught behavioral sleep techniques by nurses over 1 to 3 individual consultations when their babies were 8 to 10 months old. The control group received usual care.

Who was blinded. Allocation was concealed, and the researchers measuring outcomes did not know which group a family was in. The parents did know.

Who came back. At age 6, 225 families (69%) took part in the follow-up.

What the age-6 follow-up measured, and found

The researchers looked at three groups of outcomes: the child, the child-parent relationship, and the mother. The abstract reports no evidence of differences between the intervention and control families for any outcome. Some of the figures behind that:

Child emotional and conduct behavior scores: no difference (P = .8 and P = .6).
Sleep problems: 9% in the intervention group vs 7% in the control group (P = .2).
Chronic stress in children: 29% vs 22% (P = .4).
Child-parent closeness (P = .1), conflict (P = .4) and disinhibited attachment (P = .3): no difference.
Parent depression, anxiety and stress scores (P = .9): no difference.
Authoritative parenting: 63% vs 59% (P = .5).

None of those differences was statistically significant. In plain terms, by the time the children were 6, a researcher looking at these measures could not tell which families had been taught the techniques.

The authors’ conclusion was that behavioral sleep techniques have no marked long-lasting effects (positive or negative), and that parents and health professionals can confidently use them to reduce the short- to medium-term burden of infant sleep problems and maternal depression.

Our research page has a shorter summary if you want to share it with a partner.

What happened before age 6

The same trial reported earlier results that help explain why families might choose sleep training even if nothing differs at 6.

At 10 and 12 months, fewer families in the intervention group reported an infant sleep problem: 56% vs 68% at 10 months, and 39% vs 55% at 12 months. Mothers’ depression scores were lower and their mental health scores higher at both points (Hiscock et al., 2007).

At age 2, mothers in the intervention group were less likely to report clinical depression symptoms: 15.4% vs 26.4% using the community cut point, and 4.2% vs 13.2% using the clinical cut point. Neither parenting style nor child mental health differed markedly between groups (Hiscock et al., 2008).

So the overall picture from this one trial is a benefit for sleep and for mothers’ mood in the first year or two, and no measurable difference either way by age 6.

Other research on long-term effects of sleep training

Fewer studies have followed children for long. A 2016 randomized trial of 43 babies aged 6 to 16 months compared graduated extinction (the approach the Ferber method uses), bedtime fading and a control group. Twelve months later, there were no significant differences in emotional and behavioral problems, and no significant differences in secure versus insecure attachment, measured with a standard lab test called the strange situation procedure (Gradisar et al., 2016).

The 2006 American Academy of Sleep Medicine review of 52 studies found that behavioral treatments produced reliable and durable improvements, with over 80% of treated children improving in ways that lasted 3 to 6 months. It also said that more research is needed on longer-term efficacy (Mindell et al., 2006).

What the research cannot tell you

Good evidence has limits, and it is fairer to you to name them.

There are only a few long-term trials. The age-6 follow-up is one trial, in one city, and several of the other key trials also come from Australia.

Parents were not blinded. They knew whether they had been taught the techniques, which can affect what they report.

Families were taught techniques, not monitored. The trial compared families who were taught behavioral strategies with families who received usual care. It cannot say exactly how often each family used them, or which ones.

Not everyone came back. About a third of families did not take part at age 6, and that can shift results in ways that are hard to predict.

Averages are not your child. A trial tells you what happened across groups. It cannot promise anything about a single baby, in either direction.

The evidence answers the question “did children taught these methods turn out differently by 6?” well, and other questions less well. For the stress-hormone studies that often come up in these debates, see our article on reading the cortisol studies fairly.

Making the decision for your family

If long-term effects were your main worry, the most direct evidence available points to no measurable difference at age 6. That leaves the decision where it probably belongs: with what your family needs now. If everyone is exhausted and a parent’s mood is suffering, the earlier results suggest sleep training can help. If your nights are working, there is nothing you need to fix, and choosing not to sleep train is a fine choice too.

If you do go ahead, the usual ground rules apply. Wait until your baby is at least 4 months old; 6 months is the common start, and under 6 months means talking to your pediatrician first. Pause if your baby is sick, feverish or in pain and call your pediatrician. Keep every sleep safe, following the AAP safe sleep guide. Our article on whether the Ferber method is safe covers those points in more depth, and if the crying itself is what worries you, this piece on parent anxiety may help.

One thing to do tonight

Read the age-6 findings above with your partner, or send them the research page, and talk about what each of you is actually worried about. Sometimes a disagreement about sleep training comes down to a fear one person has not said out loud yet.

If you decide on the Ferber method, the Ferber app runs each interval, times every check-in and keeps a history of each night, so you can see how things are changing.

Common questions

Does sleep training affect children long term?

The longest randomized follow-up, published in Pediatrics in 2012, tracked 225 families until the children were 6. Children's outcomes at age 6 were no different whether or not families had sleep trained, including emotional and behavioral problems, sleep, stress and closeness to parents. The authors concluded the techniques have no marked long-lasting effects, positive or negative.

Does sleep training affect attachment?

The studies that measured it did not find a difference. The 2012 Australian follow-up found no differences at age 6 in child-parent closeness or disinhibited attachment, and a 2016 trial found no significant differences in secure versus insecure attachment 12 months after graduated extinction or bedtime fading.

Does sleep training help parents?

In the short to medium term, it can. In an Australian trial, mothers whose families received a sleep program were less likely to report clinical depression symptoms when their children were 2. By age 6, parents' mental health no longer differed between groups.

What are the limits of the long-term research?

There are only a few long-term trials, mostly from Australia, and parents knew which group they were in. The trials compared families taught behavioral techniques with families who were not, so they cannot say exactly how each family used the techniques at home.

Sources

Written by The Ferber team. Educational information, not medical advice. If you are worried about your child’s health, feeding or growth, talk to your pediatrician.

All articles