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Does sleep training affect attachment?

The best evidence available, several small randomized trials and one larger longitudinal study, does not show that common sleep-training methods (graduated extinction, controlled crying, bedtime fading) harm parent-infant attachment.

These studies also did not find lasting increases in infant stress hormone (cortisol) levels or negative effects on child behaviour and emotions afterward.

Strength of evidence

Mixed

Evidence comes from a handful of small randomized trials and pilot studies (as few as 14-18 infants per group) plus one larger observational cohort; sample sizes are small, and some published critiques argue the trials are underpowered to rule out harm, so results should be seen as reassuring but not definitive.

What the evidence says

Several randomized trials have directly tested this question. In one Australian RCT of infants 6-16 months, researchers compared graduated extinction and bedtime fading against a sleep-education control group. They found both sleep-training methods improved sleep without causing extra stress-hormone spikes or later problems with parent-child attachment or child emotions and behaviour.

A separate five-year follow-up of a related trial similarly found no evidence of harm to attachment from behavioural sleep interventions delivered by nurses. A large observational study following infants to 18 months also reported no adverse effects on attachment or behavioural development linked to parents' use of controlled crying.

That said, this reassurance comes with caveats. The trials are small (as few as 14 infants per group in some), and published expert commentary has pointed out that studies this size cannot statistically prove there is truly no effect, only that no harmful effect was detected. A related pilot RCT comparing more responsive settling methods to controlled crying found no cortisol differences between groups, though mothers using the more responsive approach reported feeling less stressed themselves.

Broader reviews of parenting interventions aimed at attachment, and of the sleep-attachment relationship generally, show mixed and inconsistent findings across different studies and measurement approaches, which is why we rate this evidence as mixed rather than strong. Overall, current evidence leans toward sleep training being safe for attachment when used as studied, but the research base is still fairly thin.

Sources

✓Reviewed by CH, MD, FRCPC

Reviewed by a specialist physician certified by the Royal College of Physicians and Surgeons of Canada, who has read this answer against the sources listed above and confirmed it reflects them. That is not medical advice about your child. How we review

Answer checked July 30, 2026

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