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

Abstract

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.

Full text

1
Parental use of ‘cry it out’ in infants: No adverse effects on attachment and behavioural
development at 18 months
Ayten Bilgin1, PhD
Dieter Wolke1,2, PhD, Dr rer nat h.c.
Affiliations: 1Department of Psychology, University of Warwick, Coventry, UK; 2Division of
Mental Health and Wellbeing, Warwick Medical School, University of Warwick, Coventry,
UK
Correspondence: Dieter Wolke; University of Warwick, Department of Psychology,
Coventry CV4 7AL, United Kingdom; telephone number: +44 (0)24 7657 3217; fax number:
+ 44 (0) 24 7652 4225; email: D.Wolke@warwick.ac.uk
Short Title: Outcomes of Cry-it-out
Funding Source: This study was supported by grant 1590/611 from the Health Foundation,
UK.
Financial Disclosure: Ayten Bilgin and Dieter Wolke have no financial relationships relevant
to this article to disclose.
Conflict of Interest: Ayten Bilgin and Dieter Wolke have no conflicts of interest to disclose.
Acknowledgements: We would like to thank the researchers who assisted in recruitment and
data collection: Tina Gutbrod, Libi Rust, and Karine Edme. We would also like to thank to
the participating hospitals (Addenbrookes Hospital, Cambridge; Luton and Dunstable
Hospital, Luton; and Queen Elizabeth II Hospital, Welwyn Garden City) and the parents and
their children. Furthermore, we would like to thank Eva Liu and Dr. Lara Ayala-Nunes for
providing feedback on the initial manuscript.

2
Abstract
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 of 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 UK 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.
Keywords: crying, cry-it-out, attachment
Word Count: 6887/ 6000

3
Introduction
Should you leave an infant to cry it out or respond immediately and attempt to soothe
him/her? This has been the subject of vehement discussion between attachment theorists and
behaviourists since half a century ago (Bell & Ainsworth, 1972; Gewirtz & Boyd, 1977) and
is a perennial concern for both researchers and parents (Blunden, Etherton, & Hauck, 2016;
Ramos & Youngclarke, 2006). Attachment theorists recommended mothers to provide prompt
response to infant crying according to infants’ needs. On the other hand, they have advised
against leaving infants to cry it out due to having concerns about its potential negative impact
on the development of infant-mother attachment (Bell & Ainsworth, 1972). In other words,
they have suggested that immediate responsiveness reflects sensitive parenting (Bell &
Ainsworth, 1972). Indeed, there was support for this claim in an early small-sample (N= 26)
naturalistic study conducted by Bell and Ainsworth (1972). In this study, the number of
crying episodes that is ignored by the mother, the duration of maternal unresponsiveness and
duration and frequency of the infant crying were observed at home during the first year at
each of the 4 quarters for approximately 4 hours during each visit. Findings of this study
showed that as the number of ignored crying episodes increased, the frequency of crying also
increased. Furthermore, it was shown that when the duration to respond to infant’s crying
signal increased, the duration of infant crying increased both concurrently and prospectively
(Bell & Ainsworth, 1972). It was further shown that increased crying at 3 months was
associated with insecure attachment at 12 months (Ainsworth, Blehar, Waters, & Wall, 1978).
In contrast, pure behaviourists argued that leaving infants to cry it out would reduce the
duration of crying, whereas immediate responding would reinforce the crying behaviour
(Gewirtz & Boyd, 1977).
Surprisingly, despite it being an old controversy, there have not been many attempts to
replicate the findings of Bell and Ainsworth’s (1972) study. A few early attempts revealed

4
support for the findings of Bell and Ainsworth’s (1972) study, however they had some
methodological shortcomings such as failure to measure maternal unresponsiveness, short
follow up periods (i.e., 3 months) or reporting on cross-sectional associations (Belsky,
Rovine, & Taylor, 1984; Crockenberg & Smith, 1982; Grossmann, Grossmann, Spangler,
Suess, & Unzner, 1985). In the only complete replication study (van IJzendoorn & Hubbard,
2000), a sample of 50 mother-infant dyads were recruited to examine the association between
frequency (i.e., percentage of infant crying ignored by the mother), and duration of maternal
unresponsiveness (i.e., percentage of the time infant cried before maternal response) and
consequent infant crying duration and frequency over a 9 months period. The study further
explored the association between frequency and duration of ignoring infant crying and
attachment classification at 15 months. Findings revealed that the frequency of ignoring
infant’s crying signals during the first 9 weeks particularly was associated with a decrease in
the frequency of infant crying 9 weeks later. However, there were no significant associations
between duration of infant crying before maternal response and later crying duration of the
infant. Furthermore, frequency and duration of infant crying ignored by the mother did not
differentiate infant-mother attachment classifications prospectively. Thus, waiting longer to
respond to crying may allow the infant to make attempts of self-soothing before responding.
This is contrary to the assertion by early attachment theorists that immediate responding
should reduce crying (Bell & Ainsworth, 1972) and partly supportive of a behavioural control
interpretation (Gewirtz & Boyd, 1977). Therefore, the existing two studies provided
contradictory findings.
The current study has two objectives. Firstly, to examine the association between the
frequency of parents leaving their infant to cry it out anytime during the day at term, 3 and 6
months and cry duration and frequency during infancy at subsequent assessment points (i.e.,
3, 6 or 18 months). Secondly, to investigate the association between frequency that parents

5
leave their infant to cry it out during the first 6 months of infancy and attachment type and
behavioural outcomes both directly observed or reported by the mother (i.e., social
referencing, easiness, task persistence, aggression, poor attention/hyperactivity) at 18 months
of age.
Methods
Participants
Participants were recruited at three hospitals in the East of England when they were born. The
infants were assessed longitudinally at term, 3, 6, and 18 months. The sample of this study
with complete longitudinal data comprised 73 very preterm/very low birth weight
(VP/VLBW (< 32 weeks gestation or <1500g birth weight) and 105 full-term infants and
their mothers. Previous studies revealed no difference between the VP/VLBW and full-term
samples in crying problems at 3 and 6 months and maternal sensitivity (Bilgin & Wolke,
2015, 2016). Thus, VP/VLBW and full-term samples were combined to allow for sufficient
statistical power while controlling for any effect of preterm birth in all analyses. There were
101 (56.7%) male and 77 (43.3%) female participants. The mean gestational age was 35.03
(SD = 4.91) weeks and the mean birth weight was 2408.98 (SD = 1061.81) grams. Forty-one
percent of infant participants had no siblings, 39% one sibling and the remaining 20%
participants had more than one sibling. Furthermore, 40% had low to moderate income
(yearly income of <£25k). Mean maternal age was 30.6 (SD = 5.82) and 34.5% of the infants’
mothers had education for more than 10 years (Table 1).
Measures
Leaving Infants to Cry it Out: Mothers were asked to report on the frequency of ‘Leaving
their infant to cry it out’ with the following question at term, 3, 6 and 18 months: ‘Have you
ever tried leaving your baby to cry it out during this time?’ The answers were as follows:
never, once, a few times and often. It was decided to combine the response options of ‘never’

6
and ‘once’ into one group, which comprised ‘no cry-it-out’ group since few responded
leaving their infant to cry it out ‘once’ (22 (12.8%) at term, 9 (5.1%) at 3 months, and 16
(9%) at 6 months). Thus, the analysis included three groups: no cry-it-out, a few times and
often.
Crying Duration and Crying Frequency: Mothers were asked to report how long their
infant fussed/cried during the morning, afternoon, evening and at night in minutes yesterday
at term, 3, 6, and 18 months and the number of bouts of fussing/crying during morning,
afternoon, evening and night yesterday at term, 3, and 18 months using the Crying Pattern
Questionnaire (St James-Roberts & Halil, 1991). Durations and bouts of fussing/crying
during morning, afternoon, evening and night were summed to create overall cry duration and
frequency of crying measure. The validity of this questionnaire has been shown to be
moderate to good (r= 0.51- 0.58) for cry duration and moderate for fuss/cry bouts (r=0.27-
0.51) when compared with a standard fuss/ cry seven day diary (Wolke, Meyer, & Gray,
1994).
Attachment: Attachment type was assessed at 18 months with the strange situation
procedure (SSP), a widely used and well-validated laboratory procedure to measure the
quality of attachment (Ainsworth, Blehar, Waters, & Wall, 1978). The coders were blind to
child and family characteristics and infant crying history. A third (32%) of the tapes were
randomly selected for inter-rater reliability assessment, which was found to be acceptable (κ=
0.76). A categorical variable was created to measure attachment insecurity: 0=secure versus
1=insecure (insecure-avoidant and insecure-resistant).
Attachment disorganization scores were coded according to Main and Solomon’s (1990)
continuous scale and a categorical variable was created: 0= organized versus (<5) 1=
disorganized (≥ 6). Please see supplementary file 1 for full description.

7
Observer-Rated Behaviour: Infant behaviour was assessed with two different observational
measures. The first assessment was the Play Observation Scheme and Emotion Rating
(POSER) at 18 Months (Wolke, Bilgin, & Samara, 2017). POSER is an observational
measure to rate maternal and infant behaviours, which includes play with a toy and free play,
each lasting 2.5 minutes. Scales in both sessions were rated by two independent researchers who
were blind to child characteristics. Each episode was viewed by the researchers a minimum of
three times, focusing firstly on maternal behaviours, followed by infant behaviours and mother-
infant joint behaviours. Overall, the coding procedure took approximately half an hour per infant-
mother dyad. Infant behaviours were rated on two sub-scales using 9-point Likert scales (1=
very low, 9 = very high). First, activity, intensity and persistence/attentiveness were combined
to a scale of Poor Attention/ Hyperactivity. Internal consistency was found to be moderate (α
= 0.71) and the inter-rater reliability was found to be = 0.90. Second, social referencing,
emotional tone and amount of vocalization were combined to an overall scale of Social
Referencing, i.e. showing positive emotional expression, vocalization and integrating
mothers’ suggestions in behaviour (α= 0.70). The inter-rater reliability was found to be =
0.91.
The second assessment is the Tester’s Rating of Infant Behaviour (TRIB) completed by a
trained examiner during the Bayley Scales assessment (Jaekel, Wolke, & Bartmann, 2013;
Wolke, Skuse, & Mathisen, 1990) at 18 months. Observations lasted on average 45 minutes
and 20% of the assessments were videotaped and rated by independent examiners for
reliability assessment. Behaviours were rated on a nine-point Likert scale ranging from
1=very low to 9=very high. The six rating scales attentiveness, competence, cooperativeness,
robustness/endurance, low demandingness and difficultness were combined to an overall
Scale of Task Persistence with high internal consistency (α= 0.95) and = 0.93 inter-rater
reliability. Ratings on adaptability, initial approach to examiner and emotional tone were

8
combined to a total scale labelled Easiness, which had high internal consistency (α= 0.87)
and = 0.90 inter-rater reliability.
Parent-Rated Behaviour Problems
Parents rated the behaviour of their 18-month-old infants using the Child Behaviour and
Health Questionnaire (CBHQ). The questionnaire consists of 35 items adapted from three
validated scales for older children: the Strengths and Difficulties Questionnaire (SDQ;
Goodman, 1997), ADHD Rating Scales (DuPaul, Power, Anastopoulos, & Reid, 1998) and
the Child Behaviour Checklist (CBCL; Achenbach, 1991). The two scales derived from
principal component analysis were poor attention/hyperactivity and aggression (see for
details -Supplementary Table 1) and had good internal consistency (αpoor attention/ hyperactivity = 0.84;
αaggression= 0.74).
Maternal Sensitivity
Maternal sensitivity was observed at 3 and 18 months of age. At 3 months of age, maternal
sensitivity was measured with the Mother-Infant Structured Play Assessment (MISPA; Bilgin
& Wolke, 2017) during 2 minutes of play with a toy and 2 minutes of free play. Maternal
sensitivity was coded using a 5-point scale of maternal positive emotion expression,
sensitivity, and stimulation adapted from 3 interaction coding schemes: the Play Observation
Scheme and Emotion Ratings: POSER (Wolke, 1986); the Emotional Availability Scales:
EAS (Biringen, 1993); and the Infant and Caregiver Engagement Phases: ICEP (Weinberg &
Tronick, 1998). The inter-rater reliability scores for each item were high (κ= 0.76, κ= 0.76,
κ= 0.78) and the overall internal consistency of the maternal sensitivity factor was moderate
(α= 0.73).
At 18 months, maternal sensitivity was observed with the POSER (Wolke, 1986; Bilgin &
Wolke, 2017), the same mother-child interaction observation we used to rate infant behaviour

9
(see above). The maternal sensitivity factor consisted of maternal positive emotion
expression, sensitivity, and appropriateness of play each rated on a 9-point Likert scale (1=
low; 9= high). The inter-rater reliability of each of the maternal behaviour items (κpositive emotion=
0.93, κsensitivity= 0.90, κappropriateness of play= 0.91) was high. The ratings on the three items during the
unstructured and structured play situation were totaled for an overall maternal sensitivity
score, which had high internal consistency (α= 0.90).
Statistical Analysis
Analyses were performed using SPSS Version 23. Logistic regression and multiple regression
analyses were used to analyze the association between leaving infant to cry it out at term, 3
and 6 months and the outcome variables which were a) crying duration and frequency of
crying at the subsequent assessment point (3, 6, 18 months); b) attachment (insecure or
disorganized), observer-rated behavioural development (poor attention/ hyperactivity, social
referencing (POSER) and task persistence, easiness (TRIB) and parent-rated behavioural
outcomes (poor attention/hyperactivity and aggression) at 18 months. Differences in sample
characteristics across the three groups of ’Leaving infant to cry it out’ (0= Never, 1= A few
times, 2=Often) were analyzed using X2 tests and one-way ANOVAs. We applied Bonferroni
correction to account for multiple comparisons.
Income (0= £0–£25k, 1= >£25k), preterm birth (0= Full-Term infants; FT, 1= Very
Preterm/Very Low Birthweight infants; VP/VLBW), being first born and crying duration or
frequency at the previous assessment point were included as covariates in all analyses.
Sensitivity analysis was performed, where all analyses were repeated excluding very preterm
born participants. Statistical significance was defined as p< .05.
Results
Characteristics of Participants according to Leaving Infant to Cry it Out

10
Figure 1 shows the frequency of leaving infant to cry it out during the first 18 months. The
majority of the parents reported never leaving their infants to cry it out at term (N= 109,
63.4%), although as time went on more parents reported leaving infant to cry it out a few
times (N= 50, 29.1% at term; N= 87, 48.9% at 3 months; N= 87, 52.1% at 6 months; N=65,
36.9% at 18 months) or often (N= 13, 7.6% at term; N= 23, 12.9% at 3 months; N= 13, 7.8%
at 6 months and N=55, 31.3% at 18 months).
High income mothers most frequently never left their infant to cry it out at term (69.8%) and
3 months (44.1%) (Table 2). At 6 months, mothers who never left their infant to cry it out
were older (M= 32.6, SD= 4.7) in comparison to those who left their infant to cry it out often
(M= 25.2, SD= 5.8). At 18 months, mothers who left their infant to cry it out more often had
higher maternal sensitivity (M= 6.42, SD= 1.46) in comparison to those who left their infant
to cry it out a few times (M= 5.74, SD= 1.30), while there were no differences in maternal
sensitivity during play interaction at 3 months (Table 2). Supplementary Table 2 shows the
bivariate correlations for all study variables.
Associations between Leaving Infant to Cry It Out and Cry Duration and Frequency
During Infancy
Leaving infant to cry it out a few times at term was significantly negatively associated with
crying duration at 18 months (

= -0.22, p= 0.004). Furthermore, leaving infant to cry it out
often at 3 months had significant negative association with crying duration at 18 months (

=
-0.17, p= 0.03). Otherwise, there were no significant associations between leaving infant to
cry it out and crying duration at earlier assessments (Table 3).
Leaving infant to cry it out a few times (

= -0.17, p= 0.03) or often (

= -0.18, p= 0.02) at
term were associated with frequency of crying at 3 months. No other significant associations
were found between leaving infant to cry it out and the frequency of crying (Table 3). When
the p-value was adjusted for multiple comparisons using Bonferroni correction (0.05/8=

11
0.006), only the association between leaving infant to cry it out a few times at term and
crying duration at 18 months remained significant (

= -0.22, p= 0.004). When we repeated
the analyses excluding very preterm infants, findings remained the same (Supplementary
Table 3a).
Associations between Leaving Infant to Cry It Out at term, 3 and 6 months and
Attachment at 18 Months
There were no significant associations between leaving infant to cry it out during the first 6
months and insecure or disorganized attachment at 18 months (Table 4). When we excluded
very preterm infants, findings remained the same (Supplementary Table 3b).
Associations between Leaving Infant to Cry Out at term, 3 and 6 months and
Behavioural Development at 18 Months
Table 4 shows that there were no significant associations between leaving infant to cry it out
during the first 6 months and behavioural development at 18 months as observed during a
play situation (POSER) or a cognitive assessment (TRIB). Similarly, there were no
significant associations between leaving infant to cry it out during the first 6 months and
parent rated behaviour at 18 months (Table 4). When we excluded very preterm infants and
the p-value was adjusted for multiple comparisons, findings remained the same
(Supplementary Table 3b).
Discussion
This study found firstly, that frequency of leaving infants to cry it out in the first 6
months in infancy is not associated with an increase of crying duration or frequency of crying
up to 18 months of age. Rather, cry duration was found to be lower at 18 months if parents
left their infants to cry it out for a few times at term and often at 3 months. Furthermore,
leaving infants to cry it out at term both a few times or often was negatively associated with

12
frequency of crying at 3 months. The strength of the associations was weak. Secondly,
frequency of leaving infants to cry it out in the first 6 months in infancy was not found to be
associated with either adverse behavioural effects on infant development or infant-mother
attachment at 18 months of age. Thus, whether contemporary parents respond immediately or
leave their infant to cry it out a few times or often might not be associated with short- or
long-term adverse effects on infant behaviour or quality of infant-mother relationship during
the first 18 months in this UK sample.
This study does not provide support for predictions made by either attachment theory
or learning theory. Thus, we neither recommend leaving infant to cry out nor responding
immediately. Rather our findings are consistent with an approach to parenting that is intuitive
and adapts to infant demands according to infant regulatory competencies across infancy
(Papousek & Papousek, 1996). In this UK sample, most mothers appear to intuitively follow
a differential responsiveness approach with most of them responding immediately at term and
then starting to adopt a differential response approach from 3 months onward. Crying in the
first 3 months of age is biologically driven and patterns of crying (the crying curve) have
been found to be similar across cultures and countries (Barr, 1990; Wolke et al., 2017). Up to
40% of crying in the first 3 months of life has been consistently reported to be inconsolable
independent of highly responsive “proximal” care or not (Lucassen et al., 2001; St James-
Roberts et al., 2006; Wolke et al., 2017). Furthermore, intervention studies found that
increased maternal responsiveness to crying and close physical contact (i.e. carrying of baby),
in particular for colic crying, did not reduce crying behaviour (Barr et al., 1991; Douglas &
Hill, 2011; St James-Roberts, Hurry, Bowyer, & Barr, 1995). Thus, converging evidence
suggests that neither immediate responding nor not responding during the first 3 months - as
suggested by behaviourists - alters infants’ crying duration subsequently in infancy. However,
there may be a small association between leaving infant to cry it out at term and frequency of

13
crying subsequently at 3 months. Likewise, the findings of the van Ijzendoorn and Hubbard
(2000) study, leaving infants to cry it out a few times is associated with a decrease in
frequency of crying subsequently.
Leaving an infant to cry it out might not reflect parental neglect but it may rather
reflect authoritative parenting which includes both limit-setting and high levels of emotional
warmth (Baumrind, 1967). Delayed responding has been suggested for dealing with infant
night waking signaled by infant crying from 6 months onwards. Hiscock et al. (2007) showed
that intervention involving leaving infant to cry it out gradually at 7 months decreased night
crying and thus, sleeping problems at 10 months and 12 months. This method of leaving
infant to cry it out using a graded approach corresponds with the concept of authoritative
parenting (Baumrind, 1967) and is consistent with a differential responsiveness framework
(van IJzendoorn & Hubbard, 2000; Wolke, 2019). Helping infants to learn how to regulate
their crying behaviour is a type of limit setting and considered beneficial when combined
with parental warmth (Baumrind, 1967). This is consistent with the finding here that maternal
sensitivity in play situations was not or positively associated (at 18 months) with leaving
infant cry it out. On the contrary, trying to respond to a crying infant immediately every time
might put mothers under a lot of stress, increase fatigue (Barr et al., 2014; Long et al., 2018)
and may increase depression (Petzoldt, 2018). Moreover, mothers’ own expectations of
responding to their crying infants immediately might even increase later infant night waking
(Galbally, Watson, Teti, & Lewis, 2018). For infants’ healthy development, the importance of
maternal self-care and good maternal mental health is invaluable (Kurth, Kennedy, Spichiger,
Hosli, & Stutz, 2011). Knowing that leaving infant to cry it out gradually decreases maternal
depression (Hiscock et al., 2007), it is more likely to be beneficial for infant emotional and
behavioural development in comparison to having ill effects. However, the number of studies

14
on leaving infant to cry it out is still scarce and longitudinal studies of different cohorts are
needed to confirm this finding.
The second argument put forward against leaving infants to cry it out is that it may
increase the risk of insecure mother-infant attachment as well as behavioural problems (Bell
& Ainsworth, 1972; Murray & Ramchandani, 2007). The current study found no associations
between leaving infants to cry it out during the first 6 months and insecure or disorganized
attachment at 18 months consistent with the findings of van Ijzendoorn and Hubbard’s (2000)
study. Furthermore, no associations were found between frequency of leaving infants to cry it
out and infant behaviour at 18 months. Similarly, sleep intervention studies and studies using
time-out (Knight, Albright, Deling, Dore-Stites, & Drayton, 2019) have not shown any
adverse effect of using a graded extinction approach in response to waking and crying at
night on infant-mother attachment or behaviour after one year (Gradisar et al., 2016) and 5
years (Price, Wake, Ukoumunne, & Hiscock, 2012). Indeed, a majority of parents reported to
be successful in adopting a behavioural approach in the community to deal with night waking
and crying (Honaker, Schwichtenberg, Kreps, & Mindell, 2018). The children fell asleep
faster and woke less within a week.
A further argument against leaving infants to cry it out has been the suggestion that it
may increase infants’ stress levels, which may be harmful to the infant (Etherton, Blunden, &
Hauck, 2016; Murray & Ramchandani, 2007). However, there is no empirical evidence that
leaving infants to cry it out actually induces stress to the infant. The only study on the stress
levels of infants after a 5-day intervention program including leaving infants to cry it out
gradually revealed no change in infant cortisol levels (Middlemiss, Granger, Goldberg, &
Nathans, 2012). Short and long-term chronic stress impact humans differently (Monaghan &
Haussmann, 2015) and early stress may increase adaptive strategies (Ellis & Del Giudice,
2019). It has been shown that short-term stress is beneficial in terms of its positive impact on

15
resiliency to stress in later life (Ellis & Del Giudice, 2019; Monaghan & Haussmann, 2015).
Differential responding as part of intuitive parenting provides infants the opportunity to
soothe themselves by waiting before intervening when crying and allows them to explore
ways of self-soothing, acquiring a first sense of self, and regulating their behavioural state
(Wolke, 2019). If leaving infants to cry it out is occurring within the context of a warm
mother-infant relationship, no adverse impacts have been demonstrated.
This prospective longitudinal study has several strengths, including a larger sample
than previous studies, adjustment for several important covariates, using repeated assessment
of frequency of leaving infant to cry it out during infancy, observer assessed infant-mother
attachment and the assessment of behavioural outcomes using both researcher observations
and parental reports. There are also limitations. Firstly, frequency of leaving infant to cry it
out and cry duration and frequency were assessed via maternal report. This assessment
represents maternal perception of her own behaviour and her infant’s crying behaviour. Direct
independent observation over long periods would be desirable but is less feasible in a
prospective study with a good sample size and repeated measurements. Where direct
observations of crying amounts and maternal report have been compared, the correlations
exceeded r=.80 (St James-Roberts, Hurry, & Bowyer, 1993). Furthermore, maternal report
has the benefit of capturing behaviours over longer time periods. Secondly, the correlational
design of the current study does not allow to determine if there is a causal relationship
between leaving infant to cry it out and the assessed outcomes. However, randomization in
controlled trials may not be possible due to strongly held views by parents. Thirdly,
frequency of crying was not assessed at 6 months. Thus, the current study did not allow us to
investigate the associations between leaving infant to cry out at 3 months and frequency of
crying at 6 months. Fourthly, the validity information of CBHQ measure was not available.
Nevertheless, this measure was formed by items from valid measures. Fifthly, the current

16
study did not allow to distinguish between leaving infant to cry out during daytime and night
time. Thus, we could not distinguish whether parents may wait less or longer when
intervening at day than night time. Future studies may address responsiveness to crying
during daytime and night time separately. Lastly, the current study included a large group of
infants who were born very preterm or very low birth weight (41%). All analyses were
controlled for the role of very preterm birth. Furthermore, sensitivity analysis excluding very
preterm born participants did not alter the main findings, revealing wider confidence
intervals.
In conclusion, contemporary practice by some parents 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. Nor was ‘Leaving infant to cry it out’
associated with reduced maternal sensitivity in interaction at 3 or 18 months of age. Increased
use of ‘Leaving to cry it out’ with age may indicate differential responding by mothers to aid
the development of infant self-regulation.

17
References
Achenbach, T. M. (1991). Manual for the Child Behavior Checklist/4-18 and 1991 profile.
Burlington, VT: University of Vermont, Department of Psychiatry.
Ainsworth, M., Blehar, M., Waters, E., & Wall, S. (1978). Patterns of attachment. Hillsdale,
N.J.: Erlbaum.
Ainsworth, M. D. S., Blehar, M. C., Waters, E., & Wall, S. (1978). Patterns of attachment: A
psychological study of the strange situation. Oxford, England: Lawrence Erlbaum.
Barr, R. G. (1990). The Normal Crying Curve: What Do We Really Know? Developmental
Medicine & Child Neurology, 32(4), 356-362. doi:10.1111/j.1469-
8749.1990.tb16949.x
Barr, R. G., Fairbrother, N., Pauwels, J., Green, J., Chen, M., & Brant, R. (2014). Maternal
frustration, emotional and behavioural responses to prolonged infant crying. Infant
Behav Dev, 37(4), 652-664. doi:10.1016/j.infbeh.2014.08.012
Barr, R. G., McMullan, S. J., Spiess, H., Leduc, D. G., Yaremko, J., Barfield, R., . . .
Hunziker, U. A. (1991). Carrying as colic "therapy": a randomized controlled trial.
Pediatrics, 87(5), 623-630.
Baumrind, D. (1967). Child care practices anteceding three patterns of preschool behavior.
Genet Psychol Monogr, 75(1), 43-88.
Bell, S. M., & Ainsworth, M. D. (1972). Infant crying and maternal responsiveness. Child
Dev, 43(4), 1171-1190.
Belsky, J., Rovine, M., & Taylor, D. G. (1984). The Pennsylvania Infant and Family
Development Project, III: The origins of individual differences in infant-mother
attachment: maternal and infant contributions. Child Dev, 55(3), 718-728.

18
Bilgin, A., & Wolke, D. (2015). Maternal Sensitivity in Parenting Preterm Children: A Meta-
analysis. Pediatrics, 136(1), e177-193. doi:10.1542/peds.2014-3570
Bilgin, A., & Wolke, D. (2016). Regulatory Problems in Very Preterm and Full-Term Infants
Over the First 18 Months. J Dev Behav Pediatr, 37(4), 298-305.
doi:10.1097/dbp.0000000000000297
Bilgin, A., & Wolke, D. (2017). Associations Between Feeding Problems and Maternal
Sensitivity Across Infancy: Differences in Very Preterm and Full-Term Infants. J Dev
Behav Pediatr, 38(7), 538-544. doi:10.1097/dbp.0000000000000466
Biringen, Z., Robinson, J., & Emde, R.N. (1993). The Emotional Availability Scales (2nd
ed.). Department of Human Development and Family Studies. Colorado State
University. Fort Collins.
Blunden, S., Etherton, H., & Hauck, Y. (2016). Resistance to Cry Intensive Sleep Intervention
in Young Children: Are We Ignoring Children's Cries or Parental Concerns? Children
(Basel), 3(2). doi:10.3390/children3020008
Crockenberg, S. B., & Smith, P. (1982). Antecedents of mother-infant interaction and infant
irritability in the first three months of life. Infant Behavior and Development, 5(2),
105-119. doi:https://doi.org/10.1016/S0163-6383(82)80021-0
Douglas, P., & Hill, P. (2011). Managing infants who cry excessively in the first few months
of life. BMJ, 343. doi:10.1136/bmj.d7772
DuPaul, G. J., Power, T. J., Anastopoulos, A. D., & Reid, R. (1998). ADHD Rating Scale—
IV: Checklists, norms, and clinical interpretation. New York, NY, US: Guilford Press.
Ellis, G. B., & Del Giudice, M. (2019). Developmental Adaptation to Stress: An Evolutionary
Perspective. Annual Review Of Psychology, 70(1), 111-139. doi:10.1146/annurev-
psych-122216-011732

19
Etherton, H., Blunden, S., & Hauck, Y. (2016). Discussion of Extinction-Based Behavioral
Sleep Interventions for Young Children and Reasons Why Parents May Find Them
Difficult. Journal of Clinical Sleep Medicine : JCSM : Official Publication of the
American Academy of Sleep Medicine, 12(11), 1535-1543. doi:10.5664/jcsm.6284
Galbally, M., Watson, S. J., Teti, D., & Lewis, A. J. (2018). Perinatal maternal depression,
antidepressant use and infant sleep outcomes: Exploring cross-lagged associations in a
pregnancy cohort study. J Affect Disord, 238, 218-225. doi:10.1016/j.jad.2018.05.025
Gewirtz, J. L., & Boyd, E. F. (1977). Does maternal responding imply reduced infant crying?
A critique of the 1972 Bell and Ainsworth report. Child Dev, 48(4), 1200-1207.
Goodman, R. (1997). The Strengths and Difficulties Questionnaire: a research note. J Child
Psychol Psychiatry, 38(5), 581-586.
Gradisar, M., Jackson, K., Spurrier, N. J., Gibson, J., Whitham, J., Williams, A. S., . . .
Kennaway, D. J. (2016). Behavioral Interventions for Infant Sleep Problems: A
Randomized Controlled Trial. Pediatrics. doi:10.1542/peds.2015-1486
Grossmann, K., Grossmann, K. E., Spangler, G., Suess, G., & Unzner, L. (1985). Maternal
Sensitivity and Newborns' Orientation Responses as Related to Quality of Attachment
in Northern Germany. Monographs of the Society for Research in Child Development,
50(1/2), 233-256. doi:10.2307/3333836
Hiscock, H., Bayer, J., Gold, L., Hampton, A., Ukoumunne, O. C., & Wake, M. (2007).
Improving infant sleep and maternal mental health: a cluster randomised trial.
Archives of Disease in Childhood, 92(11), 952-958. doi:10.1136/adc.2006.099812
Honaker, S. M., Schwichtenberg, A. J., Kreps, T. A., & Mindell, J. A. (2018). Real-World
Implementation of Infant Behavioral Sleep Interventions: Results of a Parental
Survey. The Journal of Pediatrics, 199, 106-111.e102.
doi:https://doi.org/10.1016/j.jpeds.2018.04.009

20
Jaekel, J., Wolke, D., & Bartmann, P. (2013). Poor attention rather than
hyperactivity/impulsivity predicts academic achievement in very preterm and full-
term adolescents. Psychol Med, 43(1), 183-196. doi:10.1017/s0033291712001031
Knight, R. M., Albright, J., Deling, L., Dore-Stites, D., & Drayton, A. K. (2019).
Longitudinal Relationship Between Time-Out and Child Emotional and Behavioral
Functioning. J Dev Behav Pediatr. doi:10.1097/dbp.0000000000000725
Kurth, E., Kennedy, H. P., Spichiger, E., Hosli, I., & Stutz, E. Z. (2011). Crying babies, tired
mothers: what do we know? A systematic review. Midwifery, 27(2), 187-194.
doi:10.1016/j.midw.2009.05.012
Long, J., Powell, C., Bamber, D., Garratt, R., Brown, J., Dyson, S., & James-Roberts, I. S.
(2018). Development of materials to support parents whose babies cry excessively:
findings and health service implications. Primary Health Care Research &amp;
Development, 1-13. doi:10.1017/S1463423617000779
Lucassen, P. L. B. J., Assendelft, W. J. J., van Eijk, J. T. M., Gubbels, J. W., Douwes, A. C., &
van Geldrop, W. J. (2001). Systematic review of the occurrence of infantile colic in
the community. Archives of Disease in Childhood, 84(5), 398-403.
doi:10.1136/adc.84.5.398
Middlemiss, W., Granger, D. A., Goldberg, W. A., & Nathans, L. (2012). Asynchrony of
mother-infant hypothalamic-pituitary-adrenal axis activity following extinction of
infant crying responses induced during the transition to sleep. Early Hum Dev, 88(4),
227-232. doi:10.1016/j.earlhumdev.2011.08.010
Monaghan, P., & Haussmann, M. F. (2015). The positive and negative consequences of
stressors during early life. Early Hum Dev, 91(11), 643-647.
doi:10.1016/j.earlhumdev.2015.08.008

21
Murray, L., & Ramchandani, P. (2007). Might prevention be better than cure? Archives of
Disease in Childhood, 92(11), 943-945. doi:10.1136/adc.2007.124628
Papousek, M., & Papousek, H. (1996). Infant colic, state regulation, and interaction with
parents: A systems approach. In M. H. B. J. L. Genevro (Ed.), Child development and
behavioral pediatrics: Toward understanding children and health (pp. 11-33).
Hillsdale, NJ: Lawrence Erlbaum.
Petzoldt, J. (2018). Systematic review on maternal depression versus anxiety in relation to
excessive infant crying: it is all about the timing. Arch Womens Ment Health, 21(1),
15-30. doi:10.1007/s00737-017-0771-4
Price, A. M. H., Wake, M., Ukoumunne, O. C., & Hiscock, H. (2012). Five-Year Follow-up
of Harms and Benefits of Behavioral Infant Sleep Intervention: Randomized Trial.
Pediatrics. doi:10.1542/peds.2011-3467
Ramos, K. D., & Youngclarke, D. M. (2006). Parenting advice books about child sleep:
cosleeping and crying it out. Sleep, 29(12), 1616-1623.
St James-Roberts, I., Alvarez, M., Csipke, E., Abramsky, T., Goodwin, J., & Sorgenfrei, E.
(2006). Infant crying and sleeping in London, Copenhagen and when parents adopt a
"proximal" form of care. Pediatrics, 117(6), e1146-1155. doi:10.1542/peds.2005-2387
St James-Roberts, I., & Halil, T. (1991). Infant crying patterns in the first year: normal
community and clinical findings. J Child Psychol Psychiatry, 32(6), 951-968.
St James-Roberts, I., Hurry, J., & Bowyer, J. (1993). Objective confirmation of crying
durations in infants referred for excessive crying. Archives of Disease in Childhood,
68(1), 82-84.
St James-Roberts, I., Hurry, J., Bowyer, J., & Barr, R. G. (1995). Supplementary carrying
compared with advice to increase responsive parenting as interventions to prevent
persistent infant crying. Pediatrics, 95(3), 381-388.

22
van IJzendoorn, M. H., & Hubbard, F. O. (2000). Are infant crying and maternal
responsiveness during the first year related to infant-mother attachment at 15 months?
Attach Hum Dev, 2(3), 371-391. doi:10.1080/14616730010001596
Weinberg, M. K., & Tronick, E. Z. (1998). Infant and Caregiver Engagement Phases system.
Children's Hospital and Harvard Medical School. Boston, MA.
Wolke, D. (1986). Play Observation Scheme and Emotion Rating. University of
Hertfordshire.
Wolke, D. (1999). The mother-infant structured play assessment (MISPA). University of
Hertfordshire.
Wolke, D. (2019). Persistence of infant crying, sleeping and feeding problems: need for
prevention. Archives of Disease in Childhood, archdischild-2019-317578.
doi:10.1136/archdischild-2019-317578
Wolke, D. (2019). Persistence of infant crying, sleeping and feeding problems: need for
prevention. Arch Dis Child. doi:10.1136/archdischild-2019-317578
Wolke, D., Bilgin, A., & Samara, M. (2017). Systematic Review and Meta-Analysis: Fussing
and Crying Durations and Prevalence of Colic in Infants. J Pediatr, 185, 55-61.e54.
doi:10.1016/j.jpeds.2017.02.020
Wolke, D., Meyer, R., & Gray, P. (1994). Validity of the Crying Pattern Questionnaire in a
sample of excessively crying babies. Journal of Reproductive and Infant Psychology,
12(2), 105-114. doi:10.1080/02646839408408873
Wolke, D., Skuse, D., & Mathisen, B. (1990). Behavioral style in failure-to-thrive infants - a
preliminary communication. Journal of Pediatric Psychology, 15(2), 237-254.
Table 1. Demographic Characteristics
Demographic Characteristics Very Preterm Full-Term Total Sample
Infant Sex: N (%)
Female 32 (43.8%) 45 (42.9%) 77 (43.3%)

23
Male 41 (56.2%) 60 (57.1%) 101 (56.7%)
Gestational Age (weeks) 29.42 (1.65) 38.94 (2.25) 35.03 (4.91)
Birth Weight (gr) 1285.75 (345.73) 3205.06 (554.13) 2408.98 (1061.81)
Birth Order: N (%)
First Born 31 (42.5%) 39 (37.1%) 70 (39.3%)
Maternal Education
10 years 45 (66.2%) 63 (64.9%) 108 (65.5%)
>10 years 23 (33.8%) 34 (35.1%) 57 (34.5%)
Maternal Age 30.5 (5.7) 30.7 (5.9) 30.6 (5.8)
Income: N (%)
£0–£25k 30 (45.5%) 38 (36.5%) 68 (40%)
>£25k 36 (54.5%) 66 (63.5%) 102 (60%)
Breastfeeding: N (%)
Term 21 (28.8%) 55 (52.4%) 76 (42.7%)
3 Months 13 (17.8%) 31 (29.8%) 44 (24.9%)
6 Months 10 (14.3%) 13 (13.4%) 23 (13.8%)
Sleeping in Parents’ Room: N (%)
Term 54 (74.0%) 76 (72.4%) 130 (73.0%)
3 Months 43 (58.9%) 60 (57.1%) 103 (57.9%)
6 Months 23 (31.5%) 0 (0.0%) 23 (12.9%)
Table 2. Characteristics of mothers and infants according to response to crying at term, 3
months, 6 months and 18 Months
Leaving Infant to Cry it Out
Total
Number
Never A few Times Often p
Term

24
Maternal Education 0.22
10 years 104 63 (60.6%) 30 (28.8%) 11 (10.6%)
>10 years 56 40 (71.4%) 14 (25%) 2 (3.6%)
Maternal Age 172 31.3 (5.3) 29.7 (6.6) 27.9 (6.4) 0.07
Income
£0–£25k 68 37 (54.4%) 21 (30.9%) 10 (14.7%) 0.01
>£25k 96 67 (69.8%) 27 (28.1%) 2 (2.1%)
Infant Sex
Female 75 67 (69.1%) 23 (23.7%) 7 (7.2%) 0.19
Male 97 42 (56%) 27 (36%) 6 (8%)
Preterm Birth
Very Preterm 67 38 (56.7%) 21 (31.3%) 8 (11.9%) 0.15
Full-term 105 71 (67.6%) 29 (27.6%) 5 (4.8%)
First born 67 46 (68.7%) 18 (26.9%) 3 (4.5%) 0.36
Breastfeeding
Yes 74 51 (68.9%) 20 (27%) 3 (4.1%) 0.23
No 98 58 (59.2%) 30 (30.6%) 10 (10.2%)
Sleeping at Parents’
Room
Yes 130 82 (63.1%) 37 (28.5%) 11 (8.5%) 0.72
No 42 27 (64.3%) 13 (31%) 2 (4.8%)
3 Months
Maternal Education
10 years 108 38 (35.2%) 52 (48.1%) 18 (16.7%) 0.10
>10 years 57 25 (43.9%) 29 (50.9%) 3 (5.3%)
Maternal Age 178 31.5 (5.5) 30.3 (5.9) 28.9 (6.2) 0.14
Income
£0–£25k 68 20 (29.4%) 34 (50%) 14 (20.6%) 0.04
>£40k 102 45 (44.1%) 48 (47.1%) 9 (8.8%)
Maternal Sensitivity 174 3.96 (0.51) 3.90 (0.61) 3.80 (0.51) 0.49
Infant Sex
Female 77 29 (37.7%) 36 (46.8%) 12 (15.6%) 0.64
Male 101 39 (38.6%) 51 (50.5%) 11 (10.9%)
Preterm Birth
Very Preterm 73 26 (35.6%) 32 (43.8%) 15 (20.5%) 0.04
Full-term 105 42 (40%) 55 (52.4%) 8 (7.6%)
First born 70 26 (37.1%) 34 (48.6%) 10 (14.3%) 0.91
Breastfeeding
Yes 44 18 (40.9%) 22 (50%) 4 (9.1%) 0.66
No 133 49 (36.8%) 65 (48.9%) 19 (14.3%)
Sleeping at Parents’
Room
Yes 103 38 (36.9%) 55 (53.4%) 10 (9.7%) 0.21
No 75 30 (40%) 32 (42.7%) 13 (17.3%)
6 Months
Maternal Education
10 years 102 37 (36.3%) 54 (52.9%) 11 (10.8%) 0.16
>10 years 53 26 (49.1%) 25 (47.2%) 2 (3.8%)
Maternal Age 167 32.6 (4.7) 30.3 (5.7) 25.2 (5.8) <0.001
Income
£0–£40k 63 21 (33.3%) 33(52.4%) 9 (14.3%) 0.06
>£40k 97 42 (43.3%) 51 (52.6%) 4 (4.1%)
Infant Sex
Female 71 23 (32.4%) 40 (56.3%) 8 (11.3%) 0.12

25
Male 96 44 (45.8%) 47 (49%) 5 (5.2%)
Preterm Birth
Very Preterm 70 30 (42.9%) 33 (47.1%) 7 (10%) 0.46
Full-term 97 37 (38.1%) 54 (55.7%) 6 (6.2%)
First born 61 20 (32.8%) 37 (60.7%) 4 (6.6%) 0.24
Breastfeeding
Yes 23 10 (43.5%) 12 (52.2%) 1 (4.3%) 0.79
No 144 57 (39.6%) 75 (52.1%) 12 (8.3%)
Sleeping at Parents’
Room
Yes 23 13 (56.5%) 9 (39.1%) 1 (4.3%) 0.22
No 144 54 (37.5%) 78 (54.2%) 12 (8.3%)
18 Months
Maternal Education
10 years 107 35 (32.7%) 38 (35.5%) 34 (31.8%) 0.51
>10 years 56 15 (26.8%) 25 (44.6%) 16 (28.6%)
Maternal Age 176 30.4 (4.9) 31.2 (6.2) 30.4 (6.1) 0.64
Income
£0–£40k 68 24 (35.3%) 25 (36.8%) 19 (27.9%) 0.57
>£40k 102 29 (28.4%) 38 (37.3%) 35 (34.3%)
Maternal Sensitivity 166 5.82 (1.46) 5.74 (1.30) 6.42 (1.46) 0.03
Infant Sex
Female 77 24 (31.2%) 29 (37.7%) 24 (31.2%) 0.98
Male 99 32 (32.3%) 36 (36.4%) 31 (31.3%)
Preterm Birth
Very Preterm 71 27 (38%) 31 (43.7%) 13 (18.3%) 0.01
Full-term 105 29 (27.2%) 34 (32.4%) 42 (40%)
First born 70 22 (31.4%) 28 (40%) 20 (28.6%) 0.75
Please note that boldface type indicates significant differences.

26
Table 3. Predicting Cry Duration and Cry Frequency During Infancy according to Frequency of Leaving Infant to Cry Out
Cry Duration at
3 Months
Cry Duration at
6 Months
Cry Duration at
18 Months
Cry Frequency at
3 Months
Cry Frequency at
18 Months
ppppp
Leaving Infant to Cry it Out at Term
Never [reference] [reference] [reference] [reference] [reference]
A Few Times -0.08 0.24 -0.01 0.89 -0.22 0.004 -0.17 0.03 -0.03 0.69
Often 0.07 0.35 -0.05 0.56 0.05 0.54 -0.18 0.02 -0.04 0.61
Leaving Infant to Cry it Out at 3 Months
Never [reference] [reference] [reference]
A Few Times 0.01 0.88 -0.03 0.74 0.13 0.09
Often -0.05 0.51 -0.17 0.03 -0.10 0.24
Leaving Infant to Cry it Out at 6 Months
Never [reference] [reference]
A Few Times 0.15 0.06 0.14 0.09
Often -0.07 0.36 -0.11 0.18
Please note that the analysis was controlled for income, preterm birth, first born and cry duration in the previous assessment for each regression

27
Table 4. Predicting Attachment and Behavioural Outcomes at 18 Months According to Leaving Infant to Cry it Out at Term, 3 and 6 Months
Observer Ratings Parent Ratings
POSER TRIB
Insecure
Attachment
Disorganized
Attachment
Poor Attention/
Hyperactivity
Social
Referencing
Task Persistence Easiness Poor attention/
Hyperactivity
Aggression
OR 95%
CI
OR 95%
CI
pppppp
Leaving infants to Cry it Out at Term
Never
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
A
Few
Times
0.83 0.39-
1.78
0.61 0.26-
1.47
0.05 0.53 -0.09 0.25 -0.02 0.78 -0.02 0.75 -0.03 0.6
7
0.02 0.79
Often
0.87 0.23-
3.3
0.81 0.19-
3.51
-0.08 0.32 -0.09 0.27 -0.06 0.46 -0.06 0.42 0.08 0.3
6
0.03 0.72
Leaving infants to Cry it Out at 3 Months
Never
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
A
Few
Times
1.01 0.53-
1.95
0.87 0.42-
1.83
0.05 0.50 -0.12 0.12 -0.06 0.44 -0.05 0.52 -0.03 0.7
2
-0.08 0.29
Often
1.19 0.46-
3.10
0.66 0.21-
2.07
0.02 0.77 -0.01 0.92 -0.01 0.94 -0.01 0.97 -0.03 0.7
2
0.04 0.60
Leaving infants to Cry it Out at 6 Months
Never
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
[reference
]
A
Few
Times
1.20 0.58-
2.46
0.86 0.39-
1.91
0.05 0.52 0.01 0.92 -0.09 0.29 -0.08 0.32 -0.05 0.5
9
0.05 0.60
Often
1.12 0.31-
4.10
1.10 0.27-
4.80
0.03 0.74 -0.07 0.39 0.05 0.51 0.05 0.54 -0.07 0.4
3
0.07 0.39

28
Please note that the analysis was controlled for income, preterm birth, first born and cry duration in the previous assessment for each regression. POSER: Play Observation
Scheme and Emotion Rating; TRIB: Tester’s Rating of Infant Behaviour
Term 3 Months 6 Months 18 Months
0
20
40
60
80
100
120
109
68 67
56
50
87 87
65
13
23
13
55
Never A few times Often
Figure 1. Frequency of leaving infant to cry out at term, 3, 6, and 18 months