Bilgin & Wolke (2020): Parental Use of Cry-It-Out (Journal of Child Psychology and Psychiatry)
A widely-cited study reports no adverse effects of cry-it-out at 18 months
Study of 178 infants followed to 18 months. Bilgin & Wolke reported no adverse effects of "leaving infant to cry it out" on attachment or behavioural development at 18 months. The paper has been heavily critiqued for power and analytical choices and is included here as the strongest counter-evidence in the field alongside Hiscock.
Bilgin and Wolke published a 2020 paper in the Journal of Child Psychology and Psychiatry examining whether parental use of cry-it-out affects infant attachment and behavioural development. The team followed 178 infants and their mothers, measured parental use of leaving the infant to cry at term, 3, 6, and 18 months, and assessed attachment at 18 months using the strange situation procedure plus parent-reported and observational behavioural measures. The headline finding was that contemporary parental use of cry-it-out in the first 6 months was not associated with adverse attachment or behavioural development at 18 months. The paper generated substantial controversy.
Commentaries by Davis and Kramer (2021) and others argued the study was underpowered for the kinds of subtle attachment effects predicted by theory and that the analytical choices may have overstated the null finding. Both the original paper and the critiques sit in the literature side by side.
178
Infants in the study
18 months
Follow-up duration
No adverse
Effects reported
JCPP
Journal of Child Psych & Psychiatry
Why it matters
This paper is one of the two strongest pieces of evidence (alongside Hiscock 2012) used to argue cry-it-out is harmless. The methodological critiques are part of the record, and the case for sleep training has not been settled by this paper.
This is one finding from the research library behind How to Birth a Mother. Everything here traces back to a study, a dataset, or a systematic review.