Parental use of 'cry it out' in infants: no adverse effects on attachment and behavioural development at 18 months

Background Leaving infant to cry it out has been the subject of discussion among researchers and parents. Nevertheless, there is paucity of empirical research investigating the association between leaving infant to cry it out and consequent crying duration and frequency, mother-infant attachment and behavioural development. Methods The sample with complete longitudinal data comprised 178 infants and their caretakers. Parental use of 'leaving infant to cry out' and cry duration were assessed with maternal report at term, 3, 6 and 18 months, and frequency of crying was assessed at term, 3 and 18 months of age. Attachment was measured at 18 months using the strange situation procedure. Behavioural development of the infant was assessed with two observational measures and a parent-report questionnaire at 18 months. Results The use of 'leaving infant to crying' was rare at term and increased over the next 18 months. 'Leaving infants to cry it out' at term was associated with a decrease in crying frequency at 3 months. Furthermore, leaving infants to cry it out a few times at term and often at 3 months was associated with shorter fuss/cry duration at 18 months of age. No adverse impacts of leaving infants to cry it out in the first 6 months on infant-mother attachment and behavioural development at 18 months were found. Conclusions Contemporary practice of some parents in the United Kingdom to occasionally or often 'leaving infant to cry it out' during the first 6 months was not associated with adverse behavioural development and attachment at 18 months. Increased use of 'leaving to cry it out' with age may indicate differential responding by parents related to infant self-regulation.