Diurnal cortisol secretion at home and in child care: a prospective study of 2-year-old toddlers

Evaluating perioperative stresses in children by noninvasive modalities using salivary cortisol and autonomic reactivity

PURPOSE

Salivary cortisol (SalC) and low to high pulse ratio (LHR) were used for evaluating perioperative stresses in children.

METHODS

Children aged 6 months-16 years having elective general (thoracic/abdominal) or minor (open/minimally invasive: MI) procedures underwent pulse monitoring during AM (08:00-12:00) and PM (17:00-21:00) saliva collections from the day before surgery (S-1) to 3 days after surgery (S + 3). SalC/LHR were correlated with age, sex, caregiver attendance, operative time, and surgical site/approach using mixed model analysis and face/numeric pain rating scales (FRS/NRS).

RESULTS

Mean ages (years): minor-open (n = 31) 4.7 ± 2.0, thoracic-open (n = 2) 8.7 ± 4.9, thoracic-MI (n = 6) 9.6 ± 6.1, abdominal-open (n = 14) 4.3 ± 4.1, and abdominal-MI (n = 32) 8.0 ± 5.0. Postoperative SalC increased rapidly and decreased to preoperative levels by S + 3 (p < 0.001). LHR increased slightly without decreasing (p = 0.038). SalC correlated positively with operative time (p = 0.036) and open surgery (p = 0.0057), and negatively with age (p < 0.0001) and caregiver attendance (p < 0.001). SalC correlated positively with FRS (n = 51) at S + 2(PM) (p = 0.023), S + 3(AM) (p < 0.001), S + 3(PM) (p = 0.012) and NRS (n = 34) at S + 1(AM) (p = 0.031), S + 3(AM) (p < 0.044). LHR positively correlated with age (p = 0.0072), female sex (p = 0.0047), and caregiver attendance (p = 0.0026). Postoperative SalC after robotic-assisted MI was significantly lower than after open surgery at S + 2(AM) (p = 0.020).

CONCLUSIONS

SalC correlated with pain. Caregiver attendance effectively alleviated stress.

Latent profile analysis of diurnal cortisol patterns at the ages of 2, 3.5, and 5 years: Associations with childcare setting, child individual characteristics, and maternal distress

This study performed latent profile analysis from more than 4000 saliva cortisol samples collected from children at the ages of 2 (T1), 3.5 (T2), and 5 years (T3). Three clearly different cortisol profiles were identified. The largest group at every age point was the Low/Regular latent profile, in which the cortisol slopes followed typical diurnal variation. A smaller proportion of the children belonged to the latent profile with relatively Low/Flat slope, and a minority belonged to the High/Fluctuating latent group, where the overall cortisol values and variations between the slopes were clearly higher than in the other groups. Most of the children who belonged to the High/Fluctuating group were cared for at home, they had higher temperamental surgency and their mothers had more depressive symptoms than in the other latent profile groups. However, only moderate intraindividual stability in diurnal cortisol profiles was observed across the follow-up period. On average, half of the children moved between the groups from T1 to T3. Neither child temperament, social competence, nor sex explained the stability or movement between the groups across age. Variations in cortisol profiles may be caused by the child's age, and diurnal cortisol rhythm becomes more regular along with development. Methodological issues regarding saliva cortisol research in young children are discussed. Also, more longitudinal research is needed to clarify mechanisms between environmental as well as individual factors and possible dysregulation in a child's HPA axis functioning.

Change in toddlers' cortisol activity during a year in childcare. Associations with childcare quality, child temperament, well-being and maternal education

Elevated levels of the stress hormone cortisol have been found in toddlers in childcare. Measuring cortisol may provide an indication of children's experiences in childcare and help to adjust practices better to their needs. To the best of our knowledge, toddlers' cortisol levels in childcare have not yet been investigated longitudinally. Furthermore, it is unclear which child and childcare factors contribute to cortisol elevation in toddlers. Using linear mixed model analyses, we investigated the full-day cortisol activity (10.00 h, 15.00 h, 18.00 h) of 156 toddlers (81 female, 56 male) during a year in childcare (September, January, June). We also investigated child cortisol levels at home in January. In addition, we tested the relation between cortisol activity and changes in cortisol activity across the year and childcare quality, temperament, well-being in childcare, and maternal education. We found increasing evening cortisol levels through the year while controlling for age. Afternoon cortisol levels were stable, but above morning cortisol levels in September and January and only slightly below morning cortisol levels in June. At home in January, afternoon levels were significantly below morning levels. Higher well-being in childcare was associated with lower overall cortisol levels and less increase in evening cortisol levels through the year in childcare. Further, less active toddlers seemed to accumulate some stress during the childcare day, indicated by higher evening cortisol levels. Rising evening cortisol levels may indicate accumulating stress across the year. Results point toward childcare being demanding for toddlers and their need for consideration from caregivers and parents, also after a longer period of childcare attendance. The findings underline the importance of observing, promoting, and further researching children's well-being in childcare.

Psychophysiological adjustment to formal education varies as a function of peer status and socioeconomic status in children beginning kindergarten

The transition to kindergarten can be stressful as children adjust to novel separations from their caregivers and become accustomed to their peer group. A 9-month study of 96 children (M_age  = 5.37 years, SD = 0.42) from Barranquilla, Colombia, assessed socioeconomic differences in hypothalamic-pituitary-adrenal (HPA) axis functioning across the kindergarten year. Children were from four different classrooms in one school. Saliva samples were collected twice a day across 3 consecutive days at the beginning and end of the school year. We examined whether change in HPA axis activation across the year varied as a function of a child's socioeconomic status (SES) and experience in the peer group. We found that rejected children and lower SES children had lower cortisol levels early in the morning. Rejected children had a flatter morning cortisol slope. Lower SES children had higher cortisol than their higher SES peers at the end of the school year and a flatter morning cortisol slope. Taken together, these findings suggest that diurnal cortisol in children beginning kindergarten may be influenced by both peer rejection and SES.

Children's diurnal cortisol output and temperament in two different childcare settings at 2 and 3.5 years of age

Prior research suggests that child temperament may play an important role in early childhood stress regulation. We compared children's diurnal cortisol and the association between cortisol and temperament in two different childcare settings. Cortisol was measured from saliva samples over 2 days in children (N = 84) attending out-of-home childcare and in children (N = 27), who were cared for at home at the age of 3.5 years. There was no difference between the childcare groups in total diurnal cortisol. However, of the individual measurements, afternoon cortisol levels were higher in the out-of-home childcare group during their childcare day when compared with their home day. Child temperament was not associated with total diurnal cortisol. Comparison with our prior measurements showed that the association between temperamental surgency/extroversion and total diurnal cortisol diminished along with the child age from 2 to 3.5 years in both childcare settings. This may indicate that more extroverted children are physiologically more reactive to environmental stimuli when they are younger, but this association does not appear as the children develop. Our results further suggest that the afternoon hours in the out-of-home childcare may be demanding and accelerate the hypothalamus-pituitary-adrenal axis activation in young children independent of their age.

Toddlers' diurnal cortisol levels affected by out-of-home, center-based childcare and at-home, guardian-supervised childcare: comparison between different caregiving contexts

Previous research suggests that attending non-parental out-of-home childcare is associated with elevated cortisol levels for some children. We aimed to compare diurnal saliva cortisol levels between children having out-of-home, center-based childcare or those having at-home, guardian-supervised childcare in Finland. A total of 213 children, aged 2.1 years (SD = 0.6), were drawn from the ongoing Finnish birth cohort study. Saliva samples were collected over 2 consecutive days (Sunday and Monday), with four samples drawn during each day: 30 min after waking up in the morning, at 10 am, between 2 and 3 pm, and in the evening before sleep. These results suggest that the shapes of the diurnal cortisol profiles were similar in both childcare groups following a typical circadian rhythm. However, the overall cortisol levels were on average 30% higher (95% CI: [9%, 54%], p = .004) with the at-home childcare in comparison with the out-of-home childcare group. Furthermore, a slight increase in the diurnal cortisol pattern was noticed in both groups and in both measurement days during the afternoon. This increase was 27% higher ([2%, 57%], p = .031) in the out-of-home childcare group during the out-of-home childcare day in comparison with the at-home childcare day. The elevated afternoon cortisol levels were partly explained by the afternoon naps, but there were probably other factors as well producing the cortisol rise during the afternoon hours. Further research is needed to define how a child's individual characteristic as well as their environmental factors associate with cortisol secretion patterns in different caregiving contexts.

Impact of a social skills program on children's stress: A cluster randomized trial

BACKGROUND

Most preschool children in Western industrialized countries attend child care during the day while parents work. Studies suggest that child care may be stressful to young children, perhaps because they still lack the social skills to interact daily in a group setting away from parents. This gap in social abilities may be greater for children in lower-income families, who may face more adversity at home, with fewer resources and more social isolation.

METHODS

We conducted a cluster-randomized controlled trial in 2013-2014 to test whether a social skills intervention led by early childhood educators within the child care center could reduce diurnal cortisol levels to more typical patterns expected of children this age. We randomized 19 public child care centers (n = 361 children) in low-income neighborhoods of Montreal, Canada, to either: 1) the Minipally program - intervention group (n = 10 centers; 186 children), or 2) waiting list - control group (n = 9 centers; 175 children). Saliva samples for cortisol levels were collected 3 times/day, pre- and post-implementation. The Minipally puppet program consists of 2 workshops/month for 8 months for the development of social skills and self-regulation in 2-5-year-olds, with reinforcement activities between workshops. Educators received 2-days' training and 12 h' supervision in Minipally.

RESULTS

Linear mixed models for repeated measures revealed a significant interaction between intervention status and time of day of cortisol sampling (β = -0.18, p =  0.04). The intervention group showed patterns of decreasing diurnal cortisol secretion (β = -0.32, p < 0.01), whereas the control group showed increasing slopes (β = 0.20, p < 0.01). Moreover, family income was a moderator; children in lower-income families benefited most from the intervention.

CONCLUSION

Results suggest that a social skills training program, when integrated into a preschool education curriculum, can foster an environment more conducive to typical childhood patterns of cortisol secretion.

Testing the impact of a social skill training versus waiting list control group for the reduction of disruptive behaviors and stress among preschool children in child care: the study protocol for a cluster randomized trial

Background

Most preschoolers growing up in western industrialized countries receive child care services (CCS) during the day, while their parents are at work. Meta-analytic data suggest that CCS represent a stressful experience for preschoolers. This may be because preschoolers have not yet developed the social skills necessary to cope with the new and rapidly fluctuating social contexts of CCS. We tested the effectiveness of a child care-based social skill training program aiming to improve children’s social behaviors and reduce the stress they experience.

Method and design

We used a cluster randomized control trial (cRCT) to compare children’s social behaviors and stress levels in pre- and post-intervention according to whether they received a social skill training intervention or not. Nineteen (n = 19) public CCS (n = 362, 3-years-old preschoolers) of underprivileged neighborhoods (Montreal, Canada) were randomized to one of two conditions: 1) social skills training (n = 10 CCS); or 2) waiting list control group (n = 9 CCS). Educators in the intervention group conducted bi-weekly social skills training sessions over a period of 8 months. The intervention covered four topics: making social contacts, problem solving, emotional self-regulation, as well as emotional expression and recognition. Main outcome measures included preschoolers’ disruptive (e.g. aggression, opposition, conflicts) and prosocial behaviors (e.g. sharing toys, helping another child), and stress levels assessed by salivary cortisol sampling at pre and post intervention assessments. Educators’ practices will be tested as potential mediators of the expected changes in behaviors and neuroendocrine stress.

Discussion

To our knowledge, this is the first cRCT to test the effectiveness of a child care based social skill training program on the reduction of disruptive behaviors and levels of stress. Significant challenges include the degree of adherence to the intervention protocol as well educators and preschoolers’ turnover.

Trial registration

Current clinical trial number is ISRCTN84339956 (Ongoing study, Retrospectively registered on March 2017) No amendment to initial protocol.

Electronic supplementary material

The online version of this article (doi:10.1186/s40359-017-0197-9) contains supplementary material, which is available to authorized users.

Social Buffering of Stress in Development: A Career Perspective

This review provides a broad overview of my research group's work on social buffering in human development in the context of the field. Much of the focus is on social buffering of the hypothalamic-pituitary-adrenocortical (HPA) system, one of the two major arms of the mammalian stress system. This focus reflects the centrality of the HPA system in research on social buffering in the fields of developmental psychobiology and developmental science. However, buffering of the cardiovascular and autonomic nervous system is also discussed. The central developmental question in this area derives from attachment theory, which argues that the infant's experience of stress and arousal regulation in the context of her early attachment relationships is not an immature form of social buffering experienced in adulthood but rather the foundation out of which individual differences in the capacity to gain stress relief from social partners emerges. The emergence of social buffering in infancy, changes in social buffering throughout childhood and adolescence, the influence of early experience on later individual differences in social buffering, and critical gaps in our knowledge are described.

Children's physiological responses to childcare

This review focuses on children's physiological responses to out-of-home childcare. The finding that children's cortisol levels are higher at childcare than at home has been well-replicated. Here we summarize recent evidence examining possible correlates of elevated cortisol levels. Reviewed studies suggest that childcare quality matters, whereas group sizes and type of care do not. As for child characteristics, elevated cortisol at childcare is more pronounced in toddlers than in infants, and in inhibited and aggressive children. We discuss recent advances focusing on hair cortisol analysis and immunomarkers of stress, and suggest that there is a need for experimental and longitudinal studies to examine causal relations and possible negative long-term consequences for children's health and development.

Links between early baseline cortisol, attachment classification, and problem behaviors: A test of differential susceptibility versus diathesis-stress

The purpose of the current study was to predict concurrent levels of problem behaviors from young children's baseline cortisol and attachment classification, a proxy for the quality of caregiving experienced. In a sample of 58 children living at or below the federal poverty threshold, children's baseline cortisol levels, attachment classification, and problem behaviors were assessed at 17 months of age. We hypothesized that an interaction between baseline cortisol and attachment classification would predict problem behaviors above and beyond any main effects of baseline cortisol and attachment. However, based on limited prior research, we did not predict whether or not this interaction would be more consistent with diathesis-stress or differential susceptibility models. Consistent with diathesis-stress theory, the results indicated no significant differences in problem behavior levels among children with high baseline cortisol. In contrast, children with low baseline cortisol had the highest level of problem behaviors in the context of a disorganized attachment relationship. However, in the context of a secure attachment relationship, children with low baseline cortisol looked no different, with respect to problem behavior levels, then children with high cortisol levels. These findings have substantive implications for the socioemotional development of children reared in poverty.

The longitudinal association of the diurnal cortisol rhythm with internalizing and externalizing problems in pre-schoolers. The Generation R Study

BACKGROUND

Studies investigating the association between diurnal cortisol rhythm and behavioural problems in young children have yielded inconsistent results. We tested the hypothesis that variations in diurnal cortisol rhythm in pre-schoolers are already related to problem behaviour early in life with a cross-sectional and longitudinal design.

METHODS

This study was embedded in Generation R, a population-based cohort from foetal life onwards. Parents collected saliva samples from their infant at 5 moments during 1 day. In 322 infants aged 12-20 months, we determined the diurnal cortisol rhythm by calculating the area under the curve (AUC), the cortisol awakening response (CAR), and the diurnal slope. Problem behaviour was assessed at ages 1.5 and 3 years with the Child Behavior Checklist/1.5-5 years.

RESULTS

No cross-sectional associations between the cortisol composite measures and problem behaviour were found at 1.5 years. However, cortisol predicted change in internalizing problems as assessed from 1.5 to 3 years, but not change in externalizing problems. Children with higher AUC levels, flatter slopes and a more positive CAR at baseline were more likely to score higher on the Internalizing Problems scale (β per nmol/L AUC: 0.08, 95% CI: 0.00; 0.17, p=0.04; β per nmol/L/h slope: 0.57, 95% CI: 0.17; 0.98, p=0.006; β per nmol/L CAR: 0.04, 95% CI: 0.01; 0.08, p=0.02) at follow-up.

CONCLUSIONS

Variations in diurnal cortisol rhythm are associated with change in internalizing problems in pre-schoolers. The results suggest that variations in diurnal cortisol patterns early in life precede internalizing problems.

Examining change in cortisol patterns during the 10-week transition to a new child-care setting

The transition to out-of-home child care brings a number of challenges for children, including complex peer interactions and extended separations from parents. Children often show a midmorning to afternoon rise in cortisol on child-care days, compared to the typical diurnal decline seen at home. Changes in cortisol were examined in a wide age range of children (N = 168; 1.2 months to 8 years, M = 3.27 years) during the 10-week transition to a new child-care setting. Structural equation modeling using latent change scores showed that children experienced an increase in the cortisol rise at child care across the 10-week transition. Furthermore, child age moderated the difference between home- and child-care cortisol patterns. Findings are placed in a developmental context, and potential implications and future directions are discussed.

Neonatal amygdala lesions alter basal cortisol levels in infant rhesus monkeys

The amygdala is mostly thought to exert an excitatory influence on the hypothalamic-pituitary-adrenal (HPA) axis, although its role regulating HPA basal tone is less clear, particularly during primate development. The current study examined the effects of neonatal amygdala lesions on basal HPA function and the postnatal testosterone (T) surge of rhesus monkeys reared with their mothers in large outdoor social groups. An early morning basal blood sample was collected at 2.5 months of age, whereas at 5 months samples were collected not only at sunrise, but also at mid-day and sunset to examine the diurnal rhythm of cortisol. At 2.5 months of age sham-operated males exhibited higher cortisol than females, but this sex difference was abolished by neonatal amygdalectomy, with lesioned males also showing lower basal cortisol than controls. Although neonatal amygdalectomy did not alter the postnatal T surge, there was a positive relationship between T and basal cortisol levels. At 5 months of age, neither the sex difference in cortisol, nor its correlation with T levels were apparent any longer. Instead, the diurnal cortisol rhythm of both males and females with amygdalectomy showed a blunted decline from mid-day to sunset compared to controls. These results indicate that neonatal amygdala damage alters basal HPA function in infant rhesus monkeys, affecting males only at early ages (at 2.5 months), while leaving the postnatal T surge intact, and resulting in a flattened diurnal rhythm in both genders at the later ages. Thus, the primate amygdala has a critical influence on the HPA axis in the first few months of life.

The assessment of cortisol in human hair: associations with sociodemographic variables and potential confounders

To inform the future use of hair cortisol measurement, we have investigated influences of potential confounding variables (natural hair colour, frequency of hair washes, age, sex, oral contraceptive (OC) use and smoking status) on hair cortisol levels. The main study sample comprised 360 participants (172 women) covering a wide range of ages (1-91 years; mean = 25.95). In addition, to more closely examine influences of natural hair colour and young age on hair cortisol levels, two additional samples comprising 69 participants with natural blond or dark brown hair (hair colour sample) as well as 28 young children and 34 adults (young age sample) were recruited. Results revealed a lack of an effect for natural hair colour, OC use, and smoking status on hair cortisol levels (all p's >0.10). No influence of frequency of hair washes was seen for proximal hair segments (p = 0.335) but for the third hair segment indicating lower cortisol content (p = 0.008). We found elevated hair cortisol levels in young children and older adults (p < 0.001). Finally, men showed higher hair cortisol levels than women (p = 0.002). The present data indicate that hair cortisol measurement provides a useful tool in stress-related psychobiological research when applied with the consideration of possible confounders including age and sex.

An inventory of Canadian pregnancy and birth cohort studies: research in progress

Background

A web-based inventory was developed as a voluntary registry of Canadian pregnancy and birth cohort studies, with the objective to foster collaboration and sharing of research tools among cohort study groups as a means to enrich research in maternal and child health across Canada.

Description

Information on existing birth cohort studies conducted in Canada exclusively or as part of broader international initiatives was accessed by searching the literature in PubMed and PsychInfo databases. Additional studies were identified by enquiring about the research activities of researchers at Canadian universities or working in affiliated hospitals or research centres or institutes. Of the fifty-eight birth cohort studies initially identified, forty-six were incorporated into the inventory if they were of a retrospective and/or prospective longitudinal design and with a minimum of two phases of data collection, with the first period having occurred before, during, or shortly after pregnancy and had an initial study sample size of a minimum of 200 participants.

Information collected from each study was organized into four main categories: basic information, data source and period of collection, exposures, and outcome measures and was coded and entered into an Excel spreadsheet. The information incorporated into the Excel spreadsheet was double checked, completed when necessary, and verified for completeness and accuracy by contacting the principal investigator or research coordinator. All data collected were then uploaded onto the website of the Institute of Human Development Child and Youth Health of the Canadian Institutes of Health Research. Subsequently, the database was updated and developed as an online searchable inventory on the website of the Maternal, Infant, Child and Youth Research Network.

Conclusions

This inventory is unique, as it represents detailed information assembled for the first time on a large number of Canadian birth cohort studies. Such information provides a valuable resource for investigators in the planning stages of cohort studies and identifying current research gaps.

Adrenocortical responses to strangers in preschoolers: relations with parenting, temperament, and psychopathology

Previous research has provided inconsistent evidence for the relations between young children's hypothalamic-pituitary-adrenal (HPA) functioning and their temperament, parenting, and adjustment. Building biopsychosocial models of adjustment, we examined how temperamental inhibition and maternal punishment contributed to preschoolers' adrenocortical activity while interacting with adult strangers. We also examined whether HPA functioning moderated relations between dispositional and familial factors and children's internalizing and externalizing problems. A total of 402 preschool-aged children from three independent samples with parallel and overlapping measures were studied. Salivary cortisol levels were measured twice while interacting with adult strangers during testing protocols. Mothers reported on temperamental inhibition, maternal punishment and children's problems. Maternal punishment predicted higher cortisol levels 20 and 65 min after meeting adult strangers. Prolonged cortisol elevation was associated with having fewer externalizing problems. Boys who experienced more maternal punishment and had higher cortisol 20 min after meeting strangers manifested more externalizing problems. Girls who were more inhibited and had prolonged cortisol elevations had more internalizing problems. In accord with biopsychosocial models of psychopathology, HPA functioning in preschoolers was sensitive to variations in socialization experiences, and moderated children's risk for emotional and behavioral problems.