Infant hair cortisol: associations with salivary cortisol and environmental context

Toddler hair cortisol levels are associated with maternal prenatal depression

OBJECTIVES

Cortisol is an important metabolic hormone that regulates multiple physiologic systems. Cortisol metabolism is sensitive to early life environments, including that experienced prenatally. Limited research has evaluated factors that predict variation in maternal and offspring toddler hair cortisol, which is important since hair cortisol represents different dynamics of hypothalamic pituitary adrenal (HPA)-axis function than more common salivary or serum measures.

METHODS

To address this gap, we longitudinally evaluated whether maternal depression measured in pregnancy and 1 month postnatal was associated with maternal and offspring hair cortisol levels approximately 15 months after birth (n = 46 mothers, 40 toddlers; mean 15.6 months postnatal, SD = 2.9 months).

RESULTS

Mean depression symptoms were highest during the prenatal period. Prenatal, but not postnatal, maternal depression was associated with offspring hair cortisol levels (B = 0.095, p = .01). Maternal hair cortisol was not associated with depression measured at either time point.

CONCLUSIONS

These findings indicate that offspring hair cortisol more than a year after birth is associated with maternal prenatal depression, consistent with previous research in salivary cortisol, suggesting that long-term offspring stress physiology may be influenced by conditions experienced in utero. These findings highlight the potential for hair cortisol-a minimally invasive and easy-to-collect measure- to index toddler HPA-axis dynamics.

Hair collection protocol in 12-month-old infants

Purpose

Most studies assessing hair cortisol were conducted with adults. As specific guidelines for infant hair collection are lacking, we developed a hair collection protocol for 12-month-old infants and assessed its acceptability and feasibility.

Results

Out of the total (N = 45), 95.6 % (n = 43) of caregivers consented to the procedure, while one caregiver did not consent (2.2 %), and another requested the procedure to be halted before required amount of hair had been reached (2.2 %). Furthermore, two (4.4 %) infants did not have enough hair for collection. There was no attrition due to infant fussiness/crying.

Discussion

We learned five lessons which can help to enhance reproducibility, mother's consent, and mother-infant comfort and acceptance of the procedure. The first lesson is to have the infant sit on the caregiver's lap to ensure the infant feels safe and remains relatively still. The second is to reassure caregivers by showing hair samples representing the amount to be cut as well as by clarifying no unaesthetic gaps would be visible. The third is to caress the infant's head to habituate them to the hair manipulation and to make soap bubbles as distractors. The fourth is to take extra care when securing the lock of hair for cutting because the infant scalp is thin and malleable. The fifth is to place a precision scale in the collection room to ensure the necessary weight is reached.

Conclusion

Our hair collection protocol developed for 12-month-old infants was deemed feasible and acceptable, filled an important literature gap concerning the absence of published protocols for infants, and will contribute to increase the replicability and collection efficiency for other research teams.

The Development of Stress Reactivity and Regulation in Children and Adolescents

Adversity experienced in early life can have detrimental effects on physical and mental health. One pathway in which these effects occur is through the hypothalamic-pituitary-adrenal (HPA) axis, a key physiological stress-mediating system. In this review, we discuss the theoretical perspectives that guide stress reactivity and regulation research, the anatomy and physiology of the axis, developmental changes in the axis and its regulation, brain systems regulating stress, the role of genetic and epigenetics variation in axis development, sensitive periods in stress system calibration, the social regulation of stress (i.e., social buffering), and emerging research areas in the study of stress physiology and development. Understanding the development of stress reactivity and regulation is crucial for uncovering how early adverse experiences influence mental and physical health.

Associations between maternal stress and infant resting brain activity among families residing in poverty in the U.S

Growing evidence suggests that maternal experiences of stress shape children's functional brain activity in the first years of life. Individuals living in poverty are more likely to experience stress from a variety of sources. However, it is unclear how stress is related to resting brain activity among children born into poverty. The present study examines whether infants born into households experiencing poverty show differences in brain activity associated with maternal reports of experiencing stress. The analytic sample comprised 247 mother-infant dyads who completed maternal questionnaires characterizing stress, and for whom recordings of infant resting brain activity were obtained at 1 year of age (M=12.93 months, SD=1.66; 50% female). Mothers (40% Black, non-Hispanic, 40% Hispanic, 12% White, non-Hispanic) who reported higher stress had infants who showed more resting brain activity in the lower end of the frequency spectrum (relative theta power) and less resting brain activity in the middle range of the frequency spectrum (relative alpha power). While statistically detectable at the whole-brain level, follow-up exploratory analyses revealed that these effects were most apparent in electrodes over frontal and parietal regions of the brain. These findings held after adjusting for a variety of potentially confounding variables. Altogether, the present study suggests that, among families experiencing low economic resources, maternal reports of stress are associated with differences in patterns of infant resting brain activity during the first year of life.

Can we influence the neurological development and hair cortisol concentration of offspring by reducing the stress of the mother during pregnancy? A randomized controlled trial

The objective was to evaluate the effects of a stress management cognitive behavioural therapy followed during pregnancy on subsequent childhood on hair cortisol at birth and on neurodevelopment and Hair Cortisol Concentrations (HCC) at 6 months of age. The study sample included 48 pregnant women, divided into two groups: 24 women in the Therapy Group (TG) and 24 women who received standard pregnancy care (control group (CG); CG). To test the therapy efficacy, an evaluation of the HCC and psychological stress, psychopathological symptomatology and resilience was conducted before and after the treatment. The level of cortisol in their hair was obtained during pregnancy and that of their babies at birth. Six months after birth, a cortisol sample was taken from the hair and the babies' neurodevelopment was evaluated based on a Bayley-III test. The TG presented reductions in psychological stress and psychopathological symptomatology after treatment. On the other hand, the CG increased their cortisol concentrations between the pre and post intervention, remaining stable in the TG. Moreover, results showed that TG babies had lower cortisol concentrations at birth and obtained significantly higher cognitive and motor development scores at 6 months. These findings support that providing psychological care to pregnant women may not only have a benefit on these women's mental state, but may also benefit the neurodevelopment of their offspring.

Longitudinal association between saliva and hair cortisol concentration: A systematic comparison

Cortisol assays from hair have become increasingly common in psychoneuroendocrinological research as indicators of long-term output relevant to stress and health outcomes. Comparisons of hair cortisol concentration (HCC) with salivary samples have produced mixed findings, and it remains unclear which aspects of the diurnal salivary profile correspond most closely to HCC, and what time intervals between saliva and hair sampling are most relevant, taking the rate of hair growth into account. This longitudinal study aimed to evaluate the correspondence between HCC and parameters of total salivary cortisol output in the morning (CARauc and CARi) and during the rest of the day excluding the early morning period (DAYauc), by systematically studying three time periods - two weeks, four weeks, and six weeks - before hair sampling. At each time period, 54 female university students (mean age: 20.85 ± 1.16 years) provided three saliva cortisol samples on day 1 at 11 am, 3 pm, at bedtime, then two samples the following day on waking and 30 min after awakening. Hair strand collection (1 cm nearest the scalp) took place two weeks after the last saliva sample. Results of multivariable regressions indicate that HCC was consistently associated with DAYauc for all three time periods and with the aggregate DAYauc across days after adjusting for age, body mass index, smoking, oral contraceptive use, hair washing frequency and hair treatments. The strongest associations were found for DAYauc two weeks before hair sampling (β = 0.578, p < 0.001) and the aggregated DAYauc across all three time periods (β = 0.596, p < 0.001), although the confidence intervals overlapped those for four and six week analyses. There was no significant association between HCC and either CARauc or CARi. Our study confirms that hair cortisol could be a reliable retrospective biomarker of basal and long-term cortisol output secretion at least up to six weeks earlier. The results contribute to a better understanding of the different associations between HCC and salivary cortisol in the morning and the rest of the day, while also having implications for the use of HCC as an outcome measure in intervention and treatment research.

Protocol for the COVID-19 Wellbeing and Stress Study: a longitudinal study of parent distress, biological stress and child biopsychosocial development during the pandemic and beyond

INTRODUCTION

The COVID-19 pandemic has had a unique impact on the mental health and well-being of pregnant individuals and parents of young children. However, the impact of COVID-19-related stress during pregnancy on early child biopsychosocial development, remains unclear. The COVID-19 Wellbeing and Stress Study will: (1) investigate the impact of different forms of prenatal stress experienced during the pandemic (including objective hardship, perceived psychological distress and biological stress) on child stress biology, (2) examine the association between child stress biology and child developmental outcomes, (3) determine whether child stress biology acts as a mechanism linking prenatal stress to adverse child developmental outcomes and (4) assess whether gestational age at the onset of the COVID-19 pandemic or child sex, moderate these associations.

METHODS AND ANALYSES

The COVID-19 Wellbeing and Stress Study is a prospective longitudinal study, consisting of six time points, spanning from pregnancy to 3 years postpartum. The study began in June 2020, consisting of 304 pregnant people from Ontario, Canada. This multimethod study is composed of questionnaires, biological samples, behavioural observations and developmental assessments ETHICS AND DISSEMINATION: This study was approved by the Hamilton Integrated Research Ethics Board (#11034) and the Mount Saint Vincent University Research Ethics Board (#2020-187, #2021-075, #2022-008). Findings will be disseminated through peer-reviewed presentations and publications, community presentations, and electronic forums (social media, newsletters and website postings).

Linking specific biological signatures to different childhood adversities: findings from the HERO project

BACKGROUND

Although investigations have begun to differentiate biological and neurobiological responses to a variety of adversities, studies considering both endocrine and immune function in the same datasets are limited.

METHODS

Associations between proximal (family functioning, caregiver depression, and anxiety) and distal (SES-D; socioeconomic disadvantage) early-life adversities with salivary inflammatory biomarkers (IL-1β, IL-6, IL-8, and TNF-α) and hair HPA markers (cortisol, cortisone, and dehydroepiandrosterone) were examined in two samples of young U.S. children (N = 142; N = 145).

RESULTS

Children exposed to higher SES-D had higher levels of TNF-α (B = 0.13, p = 0.011), IL-1β (B = 0.10, p = 0.033), and DHEA (B = 0.16, p = 0.011). Higher family dysfunction was associated with higher cortisol (B = 0.08, p = 0.033) and cortisone (B = 0.05, p = 0.003). An interaction between SES-D and family dysfunction was observed for cortisol levels (p = 0.020) whereby children exposed to lower/average levels of SES-D exhibited a positive association between family dysfunction and cortisol levels, whereas children exposed to high levels of SES-D did not. These findings were partially replicated in the second sample.

CONCLUSIONS

Our results indicate that these biological response systems may react differently to different forms of early-life adversity.

IMPACT

Different forms of early-life adversity have varied stress signatures, and investigations of early-life adversities with inflammation and HPA markers are lacking. Children with higher socioeconomic disadvantage had higher TNF-α, IL-1β, and DHEA. Higher family dysfunction was associated with higher hair cortisol and cortisone levels, and the association between family dysfunction and cortisol was moderated by socioeconomic disadvantage. Biological response systems (immune and endocrine) were differentially associated with distinct forms of early-life adversities.

Continuity of psychopathology v. resilience across the transition to adolescence: role of hair cortisol and sensitive caregiving

BACKGROUND

The transition to adolescence implicates heightened vulnerability alongside increased opportunities for resilience. Contexts of early life stress (ELS) exacerbate risk; still, little research addressed biobehavioral mediators of risk and resilience across the adolescent transition following ELS. Utilizing a unique cohort, we tested biosocial moderators of chronicity in adolescents' internalizing disorders v. resilience.

METHOD

Families exposed to chronic war-related trauma, v. controls, were followed. We utilized data from three time-points framing the adolescent transition: late childhood (N = 177, Mage = 9.3 years ± 1.41), early adolescence (N = 111, Mage = 11 0.66 years ± 1.23), and late adolescence (N = 138, Mage = 15.65 years ± 1.31). In late childhood and late adolescence children's internalizing disorders were diagnosed. At early adolescence maternal and child's hair cortisol concentrations (HCC), maternal sensitivity, and mothers' post-traumatic symptoms evaluated.

RESULTS

War-exposed children exhibited more internalizing disorders of chronic trajectory and mothers were less sensitive and more symptomatic. Three pathways elucidated the continuity of psychopathology: (a) maternal sensitivity moderated the risk of chronic psychopathology, (b) maternal post-traumatic symptoms mediated continuity of risk, (c) trauma exposure moderated the association between child internalizing disorders at late childhood and maternal HCC, which linked with child HCC. Child HCC linked with maternal post-traumatic symptoms, which were associated with child disorders in late adolescence.

CONCLUSION

Results demonstrate the complex interplay of maternal and child's biosocial factors as mediators and moderators of risk chronicity across the adolescent transition following trauma. Findings are first to utilize maternal and child's HCC as biomarkers of chronic stress v. resilience during adolescence, a period of neural reorganization and personal growth that shapes the individual's lifetime adaptation.

Maternal hair cortisol predicts periodic and aperiodic infant frontal EEG activity longitudinally across infancy

Maternal stress is known to be an important factor in shaping child development, yet the complex pattern of associations between stress and infant brain development remains understudied. To better understand the nuanced relations between maternal stress and infant neurodevelopment, research investigating longitudinal relations between maternal chronic physiological stress and infant brain function is warranted. In this study, we leveraged longitudinal data to disentangle between- from within-person associations of maternal hair cortisol and frontal electroencephalography (EEG) power at three time points across infancy at 3, 9, and 15 months. We analyzed both aperiodic power spectral density (PSD) slope and traditional periodic frequency band activity. On the within-person level, maternal hair cortisol was associated with a flattening of frontal PSD slope and an increase in relative frontal beta. However, on the between-person level, higher maternal hair cortisol was associated with steeper frontal PSD slope, increased relative frontal theta, and decreased relative frontal beta. The within-person findings may reflect an adaptive neural response to relative shifts in maternal stress levels, while the between-person results demonstrate the potentially detrimental effects of chronically elevated maternal stress. This analysis offers a novel, quantitative insight into the relations between maternal physiological stress and infant cortical function.

Hair cortisol, cortisone and DHEA concentrations and the composition of microbiota in toddlers

Animal research suggests that the gut microbiota and the HPA axis communicate in a bidirectional manner. However, human data, especially on early childhood, remain limited. In this exploratory design, we investigated the connections between long-term HPA axis functioning, measured as cortisol, cortisone or dehydroepiandrosterone concentrations and their ratios from hair segments of three centimeters, and gut microbiota profiles, (measured as diversity and bacterial composition by 16 S rRNA sequencing) in healthy 2.5-year-old toddlers (n = 135) recruited from the FinnBrain Birth Cohort Study. The alpha diversity of the microbiota was studied by linear regression. Beta diversity analyses with weighted UniFrac or Bray-Curtis distances were performed using PERMANOVA. The bacterial core genus level analyses were conducted using DESeq2 and ALDEx2. These analyses suggested that hair sample concentrations of separate hormones, cortisol/cortisone and cortisol/dehydroepiandrosterone ratios were associated with various gut bacterial genera such as the Veillonella, the [Ruminococcus] torques group and [Eubacterium] hallii group, although multiple testing correction attenuated the p-values. Alpha or beta diversity was not linked with either steroid concentrations or ratios. These findings in toddlers suggest that long-term HPA axis activity may be related to genera abundancies but not to ecosystem-level measures in gut microbiota. The influence of these observed interrelations on later child health and development warrants further research.

A matter of habit? Stressful life events and cognitive flexibility in 15-month-olds

Exposure to chronic stress is associated with habitual learning in adults. We studied the origins of this association by examining the link between stressful life events and infant cognitive flexibility. The final sample consisted of N = 72 fifteen-month-old infants and their mothers. Mothers completed a survey on pre- and postnatal negative life events. To assess chronic stress physiologically, infant and maternal hair cortisol concentrations were determined for cortisol accumulation during the past 3 months. Each infant participated in two cognitive tasks in the laboratory. An instrumental learning task tested infants' ability to disengage from a habituated action when this action became ineffective (Seehagen et al., 2015). An age-adequate version of the A-not-B task tested infants' ability to find a toy at location B after repeatedly finding it at location A. Correlations between cortisol concentrations and postnatal negative life events (number, perceived impact) did not yield significance. Infant and maternal hair cortisol concentrations were not correlated. Infants' ability to shift to a new action in either task, controlled for acute stress, correlated neither with pre- and postnatal negative life events nor with cortisol concentrations. Taken together, these results indicate that the potential link between long-term stress exposure and cognitive flexibility might not be present in samples with low levels of psychosocial stress.

The association between maternal symptoms of depression and hair glucocorticoids in infants across the perinatal period

BACKGROUND

Maternal symptoms of depression constitute an early adversity for infants that is considered to exert its effects via the maternal-placental-fetal neuroendocrine axis. Previous research implicates associations between maternal prenatal symptoms of depression and infants' glucocorticoid (GC) levels shortly after birth. To date, associations have not been investigated in the early postnatal period. The current study aimed to investigate the influence of maternal perinatal symptoms of depression on infants' neonatal and postnatal hair GCs providing a retrospective reflection of integrated cortisol secretion in the intrauterine and early postnatal period, respectively.

METHODS

As part of a prospective cohort study, hair samples of infants were taken up to two weeks after delivery (N = 152) and again eight weeks after delivery (N = 165). Liquid chromatography-tandem mass spectrometry was used to determine hair cortisol and cortisone in scalp-near 2-cm hair segments. Maternal symptoms of depression were assessed during pregnancy and eight weeks postnatally based on the Edinburgh Postnatal Depression Scale.

RESULTS

Higher maternal prenatal symptoms of depression showed a significant association with higher infants' neonatal hair cortisol, when controlling for confounding variables (i.e., gestational age, mode of delivery, parity, storage time, pregnancy complications). A non-significant trend for this effect was found for the hair cortisol-to-cortisone ratio while no effect occurred for hair cortisone. No association of maternal postnatal symptoms of depression with infants' postnatal hair GCs was observed. Further exploratory analyses revealed no relationship between a change of maternal prenatal to postnatal symptoms of depression with the change from infants' neonatal to postnatal hair GC levels or postnatal hair GCs.

CONCLUSION

Our results suggest that maternal prenatal symptoms of depression are associated with dysregulated infants' hair cortisol levels mainly incorporated in the intrauterine period which, in turn, might contribute to increased susceptibility for later diseases. However, no relationship was observed in infants' hair samples additionally reflecting hair GCs of the early postnatal period. Future studies should consider research on associations between maternal symptoms of depression and infants' hair GCs also later in life and take into account additional risk factors with potential impacts on GC secretion during early infancy.

Examining attachment, cortisol secretion, and cognitive neurodevelopment in preschoolers and its predictive value for telomere length at age seven

Background

Secure attachment reflects caregiver-child relationship in which the caregiver is responsive when support and comforting are needed by the child. This pattern of bond has an important buffering role in the response to stress by the reduction of the negative experience and its associated physiological response. Disruption of the physiological stress system is thought to be a central mechanism by which early care impacts children. Early life stress causes cellular and molecular changes in brain regions associated with cognitive functions that are fundamental for early learning.

Methods

The association between attachment, cortisol response before and after the Strange Situation Experiment, and neurodevelopment was examined in a sample of 107 preschoolers at age three. Also, the predictive effect of cortisol reactivity and attachment on telomere length at age seven was investigated in a followed-up sample of 77 children.

Results

Children with insecure attachment had higher cortisol secretion and poorer neurodevelopmental skills at age three. A significant cortisol change was observed across the experiment with non-significant interaction with attachment. The attachment and neurodevelopment association was not mediated by cortisol secretion. Preschoolers' attachment and cortisol did not associate nor interacted to predict telomere length at age seven.

Conclusion

These findings add evidence to the detrimental effects of insecure attachment as an aggravator of the physiological response to stress and poorer neurodevelopment during the preschool period. Although attachment and cortisol were not predictive of telomere length, intervention policies that promote secure attachment are more likely to positively echo on several health domains.

Paid maternal leave is associated with infant brain function at 3 months of age

The first months of life are critical for establishing neural connections relevant for social and cognitive development. Yet, the United States lacks a national policy of paid family leave during this important period of brain development. This study examined associations between paid leave and infant electroencephalography (EEG) at 3 months in a sociodemographically diverse sample of families from New York City (N = 80; 53 males; 48% Latine; data collection occurred 05/2018-12/2019). Variable-centered regression results indicate that paid leave status was related to differences in EEG power (ps < .02, R² s > .12). Convergent results from person-centered latent profile analyses demonstrate that mothers with paid leave were 7.39 times as likely to have infants with EEG profiles characterized by increased higher-Hz power (95% CI, 1.9-36.9), potentially reflecting more mature patterns of brain activity.

Associations between Maternal and Offspring Hair Cortisol Concentrations and Child Behavioral Symptoms in Mother-Child Pairs with Perinatal Mental Disorders

Maternal perinatal mental disorders (PMD) are associated with developmental and behavioral problems in children, probably mediated by the programming of the hypothalamic–pituitary–adrenal (HPA) axis. Increased cortisol concentrations during the antenatal and perinatal periods have been related to long-term effects on children’s behavior and stress response. We aimed to investigate the association of hair cortisol concentrations (HCC) between mothers, with (n = 16) and without PMD (n = 30), and their children, aged between 18 and 48 months. Participants were evaluated with a clinical interview and questionnaires for the Depression Anxiety Stress Scale and the Child Behavior Checklist for ages 1½–5. Maternal and child HCCs were compared between the two groups. Children of the PMD group had increased symptoms of attention deficit hyperactivity disorder. A positive linear association between maternal and child HCC was observed only in the total sample of mother–child dyads and the control group. In the PMD group, children’s HCCs were significantly associated with child anxiety/depression symptoms. Aggressive behavior and oppositional/defiant problems correlated significantly with children’s own HCCs, and their mother’s too. These findings suggest that a chronic dysregulation of maternal and child HPA axis and their associations in the PMD dyads may underlie the linkage among prolonged maternal stress, child behavioral/emotional problems and stress responses.

Social Fear in US Infants: The Roles of Hair and Salivary Cortisol

Elevated social fear in infancy poses risk for later social maladjustment and psychopathology. Hair cortisol concentration (HCC), an index of cumulative cortisol exposure, and diurnal salivary cortisol slope, a biomarker of acute stress regulation, have been associated with social fear behaviors in childhood; however, no research has addressed their relations in infancy. Elucidating potential biomarkers of infant social fear behaviors, as well as environmental factors associated with these biomarkers, may grant insights into the ontogeny of fear behaviors that increase risk for internalizing and externalizing psychopathologies later in life. The current study used multiple linear regression to examine if infant HCC, infant diurnal cortisol slope, and income-to-needs ratios (ITN) were differentially associated with observed social fear responses to a Stranger Approach task at 12 months. Using a sample of 90 infants (M _age = 12.26m, SD = 0.81m, 50% female), results indicated that increased infant HCC was associated with increased distress vocalizations during the Stranger Approach task, while steeper diurnal cortisol slope was associated with fewer distress vocalizations. Ordinary least squares path analyses did not reveal group differences between economically strained and non-strained infants in how cortisol measures and social fear responses related. Findings underscore very early psychobiological correlates of fearfulness that may increase risk for fear-related disorders and adverse mental health symptomology across childhood.

Basal and reactive cortisol: A systematic literature review of offspring of parents with depressive and bipolar disorders

One of the most consistent biological findings in the study of affective disorders is that those with depression commonly show abnormal cortisol response, which suggests dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Children of parents with mood disorders offer the opportunity to explore the biological pathways that may confer risk for psychopathology. This review explores basal and reactive cortisol in the offspring of parents who are currently depressed or have had a history of a depressive or bipolar disorder. Using PRISMA guidelines, search terms yielded 2002 manuscripts. After screening, 87 of these manuscripts were included. Results from the literature suggest that while the degree and direction of dysregulation varies, offspring of a parent with depression tend to show elevations in both basal (particularly morning and evening) and reactive (tentatively for social stressors) cortisol levels. There were few studies focused on offspring of parents with bipolar disorder. This review also discusses implications and recommendations for future research regarding the HPA axis in the intergenerational transmission of depressive disorders.

Infant diurnal cortisol predicts sleep

The sleep-wake system is immature at birth and develops in parallel with the hypothalamic-pituitary-adrenal axis, a biological stress system of which the end product is cortisol. Perturbations in one system during infancy can maladaptively influence the maturation of the other system, leading to lasting sleep and cortisol system dysregulation and heightening the risk of enduring health problems. To better understand the early interplay between these systems, we examined whether actigraphy-derived measures of night-time sleep duration and onset were associated with cumulative exposure to cortisol, indexed by hair cortisol concentration, in 12-month-old children. Overall, early sleep onset predicted lower hair cortisol above and beyond sleep duration, family income and chaos experienced at home. Furthermore, both sleep and cortisol levels vary day to day, and temporal dependencies between daily sleep and cortisol regulation are not well understood. Thus, we assessed how the sleep characteristics on a particular evening related to salivary cortisol levels the following day and how daytime and evening cortisol related to the sleep characteristics on the same night. Lower total exposure to cortisol on a particular day was related to longer night-time sleep duration the same night, but not sleep onset. Lower salivary cortisol levels on a given evening related to earlier sleep onset the same night, but not to night-time sleep duration. Sleep duration and onset on a given night were unrelated to total cortisol exposure the following day. Findings suggest that in early development, the day-to-day relation between sleep and cortisol is not bidirectional, but more driven by diurnal cortisol.

Sociodemographics and chronic stress in mother-toddler dyads living in poverty

Experiencing chronic stress early in life is associated with later health disparities, and poverty may be a significant stressor for both mothers and children. With a sample of primarily Black and White mothers (N = 75) and toddlers (N = 71) living in poverty in the United States, we examined the direct relations between sociodemographic conditions of poverty and chronic physiological stress. Mothers completed questionnaires on sociodemographics, including mother/toddler race, mother's education, father's education, poverty level, economic hardship, marital status, unemployment status, and toddler sex. Physiological chronic stress was measured by assaying the cortisol content of 4 cm samples of hair cut from the posterior vertex of mothers and toddlers (20-24 months of age) to represent 4 months of stress. Mothers' and toddlers' chronic stress was significantly, moderately, and positively associated. Toddlers had a trending relationship of moderately higher chronic stress if they were Black compared to not Black. Mothers had significantly, moderately higher chronic stress if they were Black or had a Black toddler (compared to not Black), not married (compared to married), or were working (compared to not working). The findings suggest that these mothers, simultaneously navigating poverty and parenting a toddler, need resources to reduce chronic stress.

Father involvement in infancy predicts behavior and response to chronic stress in middle childhood in a low-income Latinx sample

Fathers' involvement in early childhood is important for children's physical, emotional, and cognitive development, particularly in low-income families. However, little is known about the longitudinal relations between early father involvement and children's later physiological responses to chronic stress and behaviors impacted by stress in the context of poverty. These issues are particularly important among Latinx immigrant families who face significant psychosocial and poverty-related risk. In the current study, we examined the relationship between father involvement in infancy and physiological chronic stress in the middle childhood period, as measured through hair cortisol concentration (HCC), and several behavioral measures (attention problems, working memory) in a Latinx immigrant sample with low income. Father involvement in infancy predicted children's later HCC, and working memory in second to third grade. Father involvement also moderated the effect of HCC on working memory, such that increased HCC predicted better working memory when fathers were not involved. These findings suggest that the fathers' involvement in infancy has lasting impacts on health and behavior and that associations between physiological and behavioral measures of stress may be moderated by differences in early father involvement.

Socioeconomic factors, stress, hair cortisol, and white matter microstructure in children

Socioeconomic disadvantage has been linked to increased stress exposure in children and adults. Exposure to stress in childhood has been associated with deleterious effects on cognitive development and well-being throughout the lifespan. Further, exposure to stress has been associated with differences in brain development in children, both in cortical and subcortical gray matter. However, less is known about the associations among socioeconomic disadvantage, stress, and children's white matter development. In this study, we investigated whether socioeconomic disparities would be associated with differences in white matter microstructure in the cingulum bundle, as has been previously reported. We additionally investigated whether any such differences could be explained by differences in stress exposure and/or physiological stress levels. White matter tracts were measured via diffusion tensor imaging in 58 children aged 5-9 years. Results indicated that greater exposure to stressful life events was associated with higher child hair cortisol concentrations. Further, physiological stress, as indexed by hair cortisol concentrations, were associated with higher fractional anisotropy in the cingulum bundle. These results have implications for better understanding how perceived and physiological stress may alter neural development during childhood.

A systematic review of the association between sleep health and stress biomarkers in children

Sleep is intimately linked with the stress response system. While the evidence for this connection has been systematically reviewed in the adult literature, to our knowledge no studies have examined this relationship in young children. Recent scientific interest in understanding the effects of adverse environments in early childhood, including an emphasis on understanding the role of sleep, highlights the importance of synthesizing the current evidence on the relationship between sleep and the stress response system in early childhood. The aim of this systematic review is to examine the relationship between sleep health and biomarkers of physiologic stress (neuroendocrine, immune, metabolic, cardiovascular) in healthy children ages 0-12 y. Following PRISMA guidelines, we identified 68 empirical articles and critically reviewed and synthesized the results across studies. The majority of studies included school-age children and reported sleep dimensions of duration or efficiency. Overall, evidence of associations between sleep health and stress biomarkers was strongest for neuroendocrine variables, and limited or inconsistent for studies of immune, cardiovascular, and metabolic outcomes. Gaps in the literature include prospective, longitudinal studies, inclusion of children under the age of 5 y, and studies using objective measures of sleep.

Associations between social adversity and young children's hair cortisol: A systematic review

Psychosocial and socioeconomic adversity in early childhood (termed 'social adversity') can have lifelong detrimental effects on health and development. Physiological stress is one proposed mechanism by which social adversity 'gets under the skin'. There is substantial research interest in whether hair cortisol, a biomarker proposed to measure the cumulative physiological stress response over time, can illustrate this mechanism. As a result, a growing number of studies have tested for associations between indicators of social adversity and child hair cortisol. The aim of this paper is to conduct a comprehensive, systematic review of the evidence for associations between indicators of social adversity and hair cortisol, specifically in young children (birth to 8 years) published any time up to 31 December 2019. The literature search identified 44 published studies that met inclusion criteria. The studies examined associations between one or more indicators of social adversity and child hair cortisol across 35 independent cohorts comprising 8370 children. Indicators of adversity examined in the identified literature included socioeconomic factors (e.g. low parental education, low income and unemployment), psychosocial factors (e.g. parent stress, poor mental health and family violence), and children's direct exposure to maltreatment, abuse and stressful events. Across all indicators of adversity, a total of 142 associations with hair cortisol were examined. Evidence of associations was limited and inconsistent; 34/142 (24%) showed evidence of a positive association between adversity and higher hair cortisol, 8/142 (6%) showed a negative association, and more than two thirds (100/142, 70%) of all examined associations were null. The collective evidence appears insufficient to conclude that there is a relationship between social adversity and hair cortisol, as a measure of physiological stress response, in young children.

Hair cortisol in mother-child dyads: examining the roles of maternal parenting and stress in the context of early childhood adversity

Physiological stress is thought to be one way that early adversity may impact children's health. How this occurs may be related to parental factors such as mothers' own stress and parenting behaviour. Hair cortisol offers a novel method for examining long-term physiological stress in mother-child dyads. The current study used hair cortisol to examine the role that maternal physiological stress and parenting behaviours play in explaining any effects of adversity on young children's physiological stress. This cross-sectional study comprised 603 mother-child dyads at child age 2 years, recruited during pregnancy for their experience of adversity through an Australian nurse home visiting trial. Hair cortisol data were available for 438 participating mothers (73%) and 319 (53%) children. Confirmatory factor analysis was used to define composite exposures of economic (e.g. unemployment, financial hardship) and psychosocial (e.g. poor mental health, family violence) adversity, and positive maternal parenting behaviour (e.g. warm, responsive). Structural equation modelling examined maternal mediating pathways through which adversity was associated with children's physiological stress. Results of the structural model showed that higher maternal and child physiological stress (hair cortisol) were positively associated with one another. Parenting behaviour was not associated with children's physiological stress. There was no evidence of any mediating pathways by which economic or psychosocial adversity were associated with children's physiological stress. The independent association identified between maternal and child hair cortisol suggests that young children's physiological stress may not be determined by exogenous environmental exposures; endogenous genetic factors may play a greater role.

Hair Cortisol Concentration as a Biomarker of Sleep Quality and Related Disorders

Cortisol is the end product of the hypothalamic-pituitary-adrenal (HPA) axis, and its production is increased mainly in stressful situations or in chronic disorders accompanied by stress enhancement. Altered cortisol concentrations have been reported in a number of neuropsychiatric diseases and sleep disorders. Cortisol concentrations have been measured using several methods, and in several matrixes, such as blood, saliva, and urine. However, lately, hair cortisol, for several reasons, has emerged as a promising biomarker of long-term retrospective HPA activation. Several experimental approaches for cortisol measurement with the corresponding concentration reference ranges and a summary of findings from scientific literature on this field are presented. There is evidence of a close relationship between HPA functional alteration and the development of neuropsychiatric disorders. Sleep disorders are the most common manifestation in several neuropsychiatric conditions, and have also been associated to cortisol alterations in both adults and children. Many studies indicate that hair cortisol constitutes a valuable tool for further contributing to existing data on salivary, plasma, or urinary cortisol concentrations in patients with sleep disorders.

Cortisol and socioeconomic status in early childhood: A multidimensional assessment

The hypothalamic-pituitary-adrenal (HPA) axis is sensitive to early life stress, with enduring consequences for biological stress vulnerability and health (Gunnar & Talge, 2008). Low socioeconomic status (SES) is associated with dysregulation of the stress hormone cortisol in early childhood. However, a mechanistic understanding of this association is lacking. Multidimensional assessment of both SES and cortisol is needed to characterize the intricate relations between SES and cortisol function in early childhood. We assessed parent-reported family income, parent education, occupational prestige, neighborhood risk, food insecurity, and household chaos for 12-month-old infants (N = 90) and 3.5-year-old children (N = 91). Hair cortisol concentration (HCC) was obtained from parent and child, indexing chronic biological stress, and diurnal salivary cortisol was measured in the children. Controlling for parent HCC, parent education uniquely predicted infant and child HCC and, in addition, neighborhood risk uniquely predicted infant HCC. Household chaos predicted bedtime salivary cortisol concentration (SCC) for both infants and children, and infant daily cortisol output. Food insecurity was associated with flattened cortisol slope in 3.5-year-old children. Parental sensitivity did not mediate relations between SES and cortisol. Results highlight the utility of SES measures that index unpredictable and unsafe contexts, such as neighborhood risk, food insecurity, and household chaos.

The social ecology of childhood and early life adversity

An increasing prevalence of early childhood adversity has reached epidemic proportions, creating a public health crisis. Rather than focusing only on adverse childhood experiences (ACEs) as the main lens for understanding early childhood experiences, detailed assessments of a child's social ecology are required to assess "early life adversity." These should also include the role of positive experiences, social relationships, and resilience-promoting factors. Comprehensive assessments of a child's physical and social ecology not only require parent/caregiver surveys and clinical observations, but also include measurements of the child's physiology using biomarkers. We identify cortisol as a stress biomarker and posit that hair cortisol concentrations represent a summative and chronological record of children's exposure to adverse experiences and other contextual stressors. Future research should use a social-ecological approach to investigate the robust interactions among adverse conditions, protective factors, genetic and epigenetic influences, environmental exposures, and social policy, within the context of a child's developmental stages. These contribute to their physical health, psychiatric conditions, cognitive/executive, social, and psychological functions, lifestyle choices, and socioeconomic outcomes. Such studies must inform preventive measures, therapeutic interventions, advocacy efforts, social policy changes, and public awareness campaigns to address early life adversities and their enduring effects on human potential. IMPACT: Current research does not support the practice of using ACEs as the main lens for understanding early childhood experiences. The social ecology of early childhood provides a contextual framework for evaluating the long-term health consequences of early life adversity. Comprehensive assessments reinforced with physiological measures and/or selected biomarkers, such as hair cortisol concentrations to assess early life stress, may provide critical insights into the relationships between early adversity, stress axis regulation, and subsequent health outcomes.

Sleep and stress in mother-toddler dyads living in low-income homes

Optimal sleeping behaviors are critical for overall development, yet some evidence suggests stress and living in a low-income environment are associated with disruptions of sleeping behaviors early in life. In this study, we investigated the association of toddler sleeping behaviors, particularly difficulties initiating and/or maintaining sleep (DIMS), and maternal and toddler prolonged stress using hair cortisol from dyads living in low-income homes. Hair cortisol was mainly sampled at the posterior vertex of mothers and toddlers (age 20-24 months) and analyzed with immunoassay (n = 94). Toddler DIMS were assessed at 15-19 and 27-31 months of age through mother-rated reports using the Tayside Children's Sleep Questionnaire. We found no associations between toddler DIMS and maternal stress. Additionally, early DIMS did not predict toddler stress. However, while controlling for early DIMS and sociodemographic factors, we found that higher toddler stress predicted greater DIMS in later toddlerhood (b = -2.28, SE = 0.98, p = .02, d_s  = 0.64). These study findings highlight the importance of understanding the role of early life stress on later sleep patterns.

Association of maternal depression and home adversities with infant hypothalamic-pituitary-adrenal (HPA) axis biomarkers in rural Pakistan

BACKGROUND

Each year, almost 35% of children are exposed to maternal depression and more grow up in persistent poverty, increasing the risk for stress-related disease and other socio-developmental deficits later in life. These impacts are likely related to chronic stress via the hypothalamic-pituitary-adrenal (HPA) axis. However, there is little evidence relating early windows of child HPA axis activity to multiple exposures.

METHODS

We investigated chronic measures of hair-derived HPA axis hormones (cortisol and dehydroepiandrosterone (DHEA)) in 104 one-year old infants from rural Pakistan and longitudinal measures of maternal depression, intimate partner violence (IPV), socio-economic status (SES), and the home environment.

RESULTS

Estimates from adjusted linear mixed effects models did not reveal consistent significant associations between infant cortisol and maternal depression or home adversities. By contrast, infants exposed to maternal depression during pregnancy had lower DHEA levels (ß= -0.18 95% confidence interval [CI]: -0.34, -0.02) as did those whose mothers experienced multiple types of IPV (ß=-4.14 95% CI: -7.42, -0.79) within one year postpartum. Higher SES had a significant positive association with infant DHEA levels (ß= 0.77 95% CI: 0.08, 1.47). Depression severity and chronicity at one year postpartum had near significant associations with infant DHEA. Measures of home environment had no observable impacts on infant HPA axis activity.

LIMITATIONS

Limitations include the modest sample size and aggregation of hair samples for analysis.

CONCLUSION

Results point to possible early HPA axis dysregulation driven by changes in DHEA activity, but not cortisol at one year of age. Findings contribute to growing research examining intergenerational transmissions of maternal depression, IPV, and household environment on infant stress-response systems.

Differential associations of parental harshness and parental disengagement with overall cortisol output at 15 years: Implications for adolescent mental health

Psychosocial stress in childhood and adolescence is linked to stress system dysregulation, although few studies have examined the relative impacts of parental harshness and parental disengagement. This study prospectively tested whether parental harshness and disengagement show differential associations with overall cortisol output in adolescence. Associations between overall cortisol output and adolescent mental health problems were tested concurrently. Adolescents from the Fragile Families and Child Wellbeing Study (FFCWS) provided hair samples for cortisol assay at 15 years (N = 171). Caregivers reported on parental harshness and disengagement experiences at 1, 3, 5, 9, and 15 years, and adolescents reported at 15 years. Both parent and adolescent reported depressive and anxiety symptoms and antisocial behaviors at 15. Greater parental harshness from 1-15 years, and harshness reported at 15 years in particular, was associated with higher overall cortisol output at 15. Greater parental disengagement from 1-15 years, and disengagement at 1 year specifically, was associated with lower cortisol output. There were no significant associations between cortisol output and depressive symptoms, anxiety symptoms, or antisocial behaviors. These results suggest that the unique variances of parental harshness and disengagement may have opposing associations with cortisol output at 15 years, with unclear implications for adolescent mental health.

Hair sampling for cortisol analysis with mother-toddler dyads living in low-income homes

BACKGROUND

A first step to advance stress science research in young children is understanding the relationship between chronic stress in a mother and chronic stress in her child. One non-invasive measure of chronic stress is hair cortisol. However, little is known about strategies for hair sampling in mother-toddler dyads living in low-income homes in the U.S. To address prior limitations, the purpose of this study was to understand the feasibility of sampling hair for cortisol analysis in mother-toddler dyads living in low-income homes in the U.S. We examined feasibility related to participation, eligibility, and gathering an adequate hair sample weight.

METHODS

We approached 142 low-income, racially diverse, urban-dwelling mothers who were participating in an ongoing longitudinal birth cohort study for informed consent to cut approximately 150 hairs from the posterior vertex of their scalp and their toddlers' (20-24 months) scalp. We demonstrated the process of sampling hair with a hairstyling doll during home visits to the mother and toddler using rounded-end thinning shears.

RESULTS

Overall, 94 of 142 mother-toddler dyads (66 %) participated in hair sampling. The most common reason for participation refusal was related to hairstyle. All but three hair samples were of adequate weight for cortisol extraction.

DISCUSSION

The findings from this study can help researchers address sampling feasibility concerns in hair for cortisol analysis research in mother-toddler dyads living in low-income homes in the U.S.

Hair cortisol and dehydroepiandrosterone concentrations: Associations with executive function in early childhood

Chronic stress during childhood negatively impacts cognition and physical and mental health. Exposure to stressors over time can cause hypothalamic-pituitary-adrenal (HPA) axis dysregulation, leading to abnormal stress hormone levels, which can be reflected in hair cortisol concentration (HCC) and hair dehydroepiandrosterone (DHEA) concentration. Although the use of HCC and DHEA to measure chronic stress in children is increasing, their effects on cognition (as indexed by executive function) remain unexplored. Accordingly, we aimed to investigate the associations of HCC, DHEA, and their ratio with measures of executive function (cognitive flexibility and working memory) in a sample of kindergarten children (N=100). We found that the expected negative association between HCC and working memory approached significance, and DHEA was significantly and positively related to cognitive flexibility. We discuss possible interpretations of our findings. Our results suggest promising areas for future investigation and encourage further exploration into HCC and DHEA as measures of chronic stress.

Examining the role of socioeconomic status and temperament in the hair cortisol levels of infants

Socioeconomic status (SES) appears to be an important contextual factor in children's developmental outcomes, including their responses to stress. However, some children are more susceptible to its effects than others. Hair cortisol is a newer method of assessing the activity of the HPA axis, providing cumulative cortisol levels. The present article examined whether temperament (negative emotionality) moderates the association between an SES index and the hair cortisol concentration (HCC) of infants. Sixty infants from 6 to 15 months of age were recruited, of which 49 had sufficient hair for cortisol analysis. The SES index was calculated from the education levels of the mothers, family income, and a scale measuring the quality of the home environment. Negative emotionality was measured with the three sub-scales of the Infant Behavior Questionnaire (falling reactivity, distress to limitations, and fear). Among infants low in negative emotionality, there was no association between SES and cortisol. In contrast, among those high in negative emotionality, a significant association was obtained. These infants showed lower levels of HCC in lower-SES environments. The findings suggest that there are individual differences in reacting to the environment, and low levels of cortisol (not high) were found in susceptible infants in lower-SES families.

Caregiver depression is associated with hair cortisol in a low-income sample of preschool-aged children

BACKGROUND

Caregiver depression and child temperamental characteristics such as effortful control have been associated with child dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Hair cortisol concentrations (HCC) has been increasingly adopted as an integrated marker of HPA axis activity. This study examined the associations between caregiver depressive symptoms, caregiver social support, child effortful control, and child HCC in a sample of a high-risk, low-income preschool-aged children.

METHODS

154 caregivers comprised mostly of mothers and their children (2-to-5 years) who were enrolled in a birth cohort study conducted in poor urban neighborhoods of São Paulo, Brazil. Through personal interviews at their homes, caregivers provided ratings of their psychosocial experiences and of their child's behavior. Hair was sampled from children with at least a 3-cm hair length.

RESULTS

In a multivariable regression analysis, an unadjusted model showed child age to be negatively associated with HCC (β = -0.32, p < .001). The adjusted model, which accounted for child age and sex, showed a positive relationship between caregiver depressive symptoms and HCC (β = 0.22, p < .01). Caregiver social support and child effortful control were not associated with HCC.

CONCLUSIONS

The elevated HCC among children with caregivers reporting greater depression risk is consistent with prior findings showing elevated HCC among children exposed to persistent stress. Stabilization of child HCC may be occurring within preschool children given the negative association between HCC and age. Greater research is needed to determine whether the effects of caregiver social support and effortful control can be captured through HCC.

Biological sensitivity to context in Pakistani preschoolers: Hair cortisol and family wealth are interactively associated with girls' cognitive skills

Many young children in low- and middle-income countries (LMICs) face heightened risk for experiencing environmental adversity, which is linked with poorer developmental outcomes. Children's stress physiology can shed light on why children are differentially susceptible to adversity. However, no known studies have examined whether links between adversity and children's development are moderated by children's stress physiology in LMICs. The present study revealed significant interactive effects of hair cortisol concentrations, an index of chronic physiological stress regulation, and family wealth on preschoolers' cognitive skills in rural Pakistan. In a sample of 535 4-year-old children (n = 342 girls), we found significant associations between family wealth and direct assessments of verbal intelligence, pre-academic skills, and executive functions only in girls with lower hair cortisol concentrations. Specifically, girls with lower cortisol concentrations displayed greater cognitive skills if they came from relatively wealthier families, but lower cognitive skills if they came from very poor families. There were no significant associations among boys. Results provide evidence of biological sensitivity to context among young girls in a LMIC, perhaps reflecting, in part, sex differences in daily experiences of environmental adversity.

Minimally-invasive methods for examining biological changes in response to chronic stress: A scoping review

BACKGROUND

Nurse researchers are increasingly interested in incorporating biological indicators related to chronic stress, or repeated or constant exposure to psychological stressors. Minimally invasive collection methods may improve access to vulnerable populations.

OBJECTIVE

To map biological indicators measured through minimally invasive methods investigating biological changes in response to chronic stress.

DESIGN, DATA SOURCES, AND METHODS

The paper seeks to answer two questions: What are the characteristics of the minimally-invasive methods used to measure the biological correlates of chronic stress? What are the limitations regarding the use of the minimally-invasive methods and/or biological indicators identified above? Authors completed a scoping review following guidelines from the Joanna Briggs Institute Manual and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for Scoping Reviews. A literature search was completed in PubMed, PsycINFO, and Scopus. 2518 articles were screened and 145 studies were included. Data were extracted using a standardized extraction tool, compiled, and coded.

RESULTS

Studies included minimally-invasive methods to measure the hypothalamic-adrenal-pituitary axis (N = 173), immune and inflammatory markers (N = 118), and adult neurogenesis (N = 6). Cortisol was most frequently measured (N = 136), usually in saliva (N = 86). Studies included a variety of limitations for the methods and indicators, including concerns about timing and accuracy of collection, frequency of sampling, and controlling for acute stressors.

CONCLUSIONS

Nurse researchers have access to many minimally-invasive methods to measure altered biological processes related to chronic stress. A gap identified by this review is the paucity of minimally-invasive methods for investigating neurogenesis; the measurement of brain derived neurotrophic factor in plasma is a distal proxy and further research is needed to test the response of peripheral levels to psychosocial stress interventions. Additionally, while this scoping review allows nurse researchers to consider possible biological indicators to include in their research, future research is still needed on some of the basic premises of stress research, including agreement on the conceptualization of chronic stress.

Refugee mother-child dyads' hair cortisol, post-traumatic stress, and affectionate parenting

Refugees are a special population who experience adversity before, during and after forced displacement. Hence, many of them show post-traumatic stress symptoms (PTSS). PTSS can be transmitted from the mother to the child and are associated with alterations in cortisol responses. Positive parenting practices, such as maternal affection, counteracts psychopathology in early childhood. The aim of this explorative study was to investigate how children's cortisol is associated with mothers' cortisol after forced displacement, and whether or not an association depends on maternal affection. A total of 42 Arabic-speaking mother-child dyads, who came to Germany as refugees from Syria or Iraq within the past four years, participated in the present cross-sectional study. All children were below the age of 5 years. We assessed children's and mothers' hair cortisol concentration (HCC) and PTSS. Additionally, we observed and objectively rated maternal affection during mother-child interactions. The association between mothers' and children's HCC, as well as their associations with maternal affection, depended on the difference between children's and mothers' HCC. Furthermore, this HCC difference significantly predicted children's PTSS. Hence, in order to understand the mechanisms underlying children's PTSS, it is essential to consider maternal variables and differential effects within samples. We discussed possible explanations for those findings.

Socioeconomic Disparities in Chronic Physiologic Stress Are Associated With Brain Structure in Children

BACKGROUND

Socioeconomic factors have been consistently linked with the structure of children's hippocampus and anterior cingulate cortex (ACC). Chronic stress-as indexed by hair cortisol concentration-may represent an important mechanism underlying these associations. Here, we examined associations between hair cortisol and children's hippocampal and ACC structure, including across hippocampal subfields, and whether hair cortisol mediated associations between socioeconomic background (family income-to-needs ratio, parental education) and the structure of these brain regions.

METHODS

Participants were 5- to 9-year-old children (N = 94; 61% female) from socioeconomically diverse families. Parents and children provided hair samples that were assayed for cortisol. High-resolution, T1-weighted magnetic resonance imaging scans were acquired, and FreeSurfer 6.0 was used to compute hippocampal volume and rostral and caudal ACC thickness and surface area (n = 37 with both child hair cortisol and magnetic resonance imaging data; n = 41 with both parent hair cortisol and magnetic resonance imaging data).

RESULTS

Higher hair cortisol concentration was significantly associated with smaller CA3 and dentate gyrus hippocampal subfield volumes but not with CA1 or subiculum volume. Higher hair cortisol was also associated with greater caudal ACC thickness. Hair cortisol significantly mediated associations between parental education level and CA3 and dentate gyrus volumes; lower parental education level was associated with higher hair cortisol, which in turn was associated with smaller volume in these subfields.

CONCLUSIONS

These findings point to chronic physiologic stress as a potential mechanism through which lower parental education level leads to reduced hippocampal volume. Hair cortisol concentration may be an informative biomarker leading to more effective prevention and intervention strategies aimed at childhood socioeconomic disadvantage.

Hair cortisol, perceived stress, and social support in mother-child dyads living in an urban neighborhood

Women and children belonging to a racial/ethnic minority bear a disproportionate burden of psychosocial stress that increases their vulnerability to adverse health outcomes. Hair cortisol has been rapidly advanced as a biomarker of the intensity and course of the stress response over time and may provide an opportunity to increase our understanding of the role of psychological stress in health. However, research on the link between hair cortisol levels and subjective measures of maternal and child stress among low-income and minority individuals is limited. The goal of this study was to examine the association between stress and hair cortisol in low income, minority women and children who experience disproportionate exposure to chronic stress. A convenience sample of 54 minority mother/child dyads from a busy primary care clinic in the second poorest medium-sized city in the US participated in the study. Mothers self-reported perceived stress, social support, household characteristics and other demographic factors, and their children (ages 7-14 years) reported on the perceived level of safety in their neighborhood and exposure to violence as markers of child stress. Three-centimeter hair samples were collected from both mothers and children during the clinic visit, and hair cortisol levels were assessed via enzyme-linked immunosorbent assays. Linear regression models examined associations between maternal and child hair cortisol, and between hair cortisol and perceived stress level in women, and moderation by social support. Maternal hair cortisol was not significantly associated with mother's perceived stress. Maternal and child hair cortisol levels were positively associated (p = .007) but this association was not moderated by maternal perceived social support. These findings suggest that hair cortisol is strongly associated among this sample of minority mother-child dyads and is not moderated by social support.

The contribution of childhood adversity to cortisol measures of early life stress amongst infants in rural India: Findings from the early life stress sub-study of the SPRING cluster randomised controlled trial (SPRING-ELS)

BACKGROUND

The majority of the world's children live in low- and middle-income countries and face multiple obstacles to optimal wellbeing. The mechanisms by which adversities - social, cultural, psychological, environmental, economic - get 'under the skin' in the early days of life and become biologically embedded remain an important line of enquiry. We therefore examined the contribution of childhood adversity through pregnancy and the first year of life to hair and salivary cortisol measures of early life stress in the India SPRING home visits cluster RCT which aims to improve early childhood development.

METHODS

We assessed 22 adversities across four domains: socioeconomic, maternal stress, family-child relationship, and child and summed them to make a cumulative adversity score & quintiles, and four subscale scores. We cut 3 cm of hair from the posterior vertex and took three saliva samples from morning till late afternoon on each of two days (total six samples). We analysed both for cortisol concentration using ELISA techniques. We used multiple linear regression techniques to assess the relationship between cumulative adversity and log hair cortisol concentration and saliva diurnal slope and area under the curve.

RESULTS

We assessed 712 children for hair, and 752 children for saliva cortisol at 12 months of age. We found a strong positive relationship between adversity and hair cortisol; each additional adversity factor was associated with hair cortisol increases of 6.1% (95% CI 2.8, 9.4, p < 0.001) and the increase from adversity quintile one to five was 59.4%. Socioeconomic, relationship and child scales were independent predictors of hair cortisol (socioeconomic 6.4% (95% CI -0.4, 13.6); relationship 11.8% (95% CI 1.4, 23.2); child 7.9% (95% CI -0.5, 16.9). We did not find any association between any measures of adversity and either of the saliva cortisol outcomes.

DISCUSSION

This is the largest study of hair cortisol in young children, and the first in a low- and middle-income country setting. Whilst the short-term diurnal measures of cortisol did not appear to be linked with adversity, chronic exposure over several months appears to be strongly associated with cumulative adversity. These findings should spur further work to understand the specific ways in which adversity becomes biologically embedded, and how this can be tackled. They also lend support to ongoing action to tackle childhood adversity in communities around the world.

Salivary and hair cortisol as biomarkers of emotional and behavioral symptoms in 6-9 year old children

The aim of the present work is to investigate the association of salivary and cumulative cortisol levels with emotional and behavioral symptoms in a Franconian Cognition and Emotion Studies (FRANCES) general population cohort of 158 6- to 9 year old children. Salivary cortisol values were measured by one-day diurnal cortisol profile, whereas cumulative cortisol was estimated via one-month hair cortisol concentrations (rHCC). Nearly all significant associations of clinical symptoms with child cortisol indices were age dependent: We report emotional symptoms being associated with lower rHCC in younger children (6.06-7.54 years). In older children (7.55-9.41 years) behavioral problems were further associated with higher rHCC and lower salivary cortisol awakening responses. In summary, child clinical symptoms were stronger associated with markers of hair cortisol compared to salivary cortisol. To picture developmental mechanisms, we suggest longitudinal designs for cortisol measures of stress systems in children and adolescents.

Emotion regulation moderates the association between parent and child hair cortisol concentrations

Successful emotion regulation facilitates children's coping with everyday stress. It develops rapidly in the early preschool period. However, no work has been done to investigate the potential buffering role of emotion regulation from cumulative physiological effects of stress. In this study, we examined hair cortisol concentration (HCC), an early marker of chronic physiological stress, socioeconomic status (SES), parental sensitivity, and emotion regulation and reactivity in a sample of 3.5-year-old children (N = 86). Emotion regulation and emotional reactivity were independent of child HCC. However, emotion regulation moderated the relationship between parent and child HCC. For children with better emotion regulation, there was no association between parent and child HCC, suggesting that emotion regulation skills buffered the transgenerational effects of chronic physiological stress. Emotional reactivity moderated the relationship between SES and child HCC, and attenuated the association between parental sensitivity and child HCC. Taken together, these findings demonstrate that children who were less emotionally reactive were less susceptible to their environments. Results provide support that child emotion regulation and emotional reactivity can reduce or strengthen the relationship between established risk factors and levels of chronic physiological stress in early childhood.

Maternal Stress During Pregnancy Is Associated with Decreased Cortisol and Cortisone Levels in Neonatal Hair

BACKGROUND

Hair glucocorticoids (GCs) offer a retrospective view on chronic GC exposure. We assessed whether maternal pre- and postnatal stress was associated with neonatal and maternal hair GCs postpartum (pp).

METHODS

On the first day pp 172 mother-infant pairs donated hair, of whom 67 had consulted a centre of expertise for psychiatric disorders during pregnancy. Maternal stress was scored on the Hospital Anxiety and Depression Scale during the first/second (n = 46), third trimester (n = 57), and pp (n = 172). Hair cortisol and cortisone levels were determined by liquid chromatography-tandem mass spectrometry, and associations with maternal hospital anxiety subscale (HAS) and hospital depression subscale (HDS) scores, and antidepressant use were analyzed with linear regression.

RESULTS

Neonatal hair GCs were negatively associated with elevated HAS-scores during the first/second trimester, log 10 (β [95% CI]) cortisol -0.19 (-0.39 to 0.02) p = 0.07, cortisone -0.10 (-0.25 to 0.05) p = 0.17; third trimester, cortisol -0.17 (-0.33 to 0.00) p = 0.05, cortisone -0.17 (-0.28 to -0.05) p = 0.01; and pp, cortisol -0.14 (-0.25 to -0.02) p = 0.02, cortisone -0.07 (-0.16 to 0.02) p = 0.10. A similar pattern was observed for elevated HDS-scores. Maternal hair GCs were positively associated with elevated HAS-scores pp (cortisol 0.17 [0.01 to 0.32] p = 0.04, cortisone 0.18 [0.06 to 0.31] p = 0.01), but not prenatally or with elevated HDS-scores. Antidepressant use was associated with elevated maternal hair GCs (p ≤ 0.05), but not with neonatal hair GCs.

CONCLUSION

Exposure to excessive pre- and perinatal maternal stress was associated with a decrease in neonatal hair GCs, while elevated stress-scores around birth were associated with increased maternal hair GCs and elevated stress-scores earlier in gestation were not associated with maternal hair GCs pp. Further studies are needed to test associations with infant neurodevelopment.

Impact of Two Forms of Daily Preventive Zinc or Therapeutic Zinc Supplementation for Diarrhea on Hair Cortisol Concentrations Among Rural Laotian Children: A Randomized Controlled Trial

Zinc supplementation has been shown to reduce the morbidity burden among young children, and may reduce chronic stress. Hair cortisol has been promoted as an indicator of chronic stress. We assessed the impact of different strategies for delivering supplementary zinc on hair cortisol concentrations (HCC) in young Laotian children and examined risk factors associated with HCC. In a randomized double-blind controlled trial (NCT02428647), children aged 6⁻23 mo were randomized to one of four intervention groups and followed for ~36 weeks: daily preventive zinc (PZ) tablets (7 mg/day), daily multiple micronutrient powder (MNP) sachets (containing 10 mg zinc and 14 other micronutrients), therapeutic zinc (TZ) supplements for diarrhea treatment (20 mg/day for 10 days) or daily placebo powder. HCC of 512 children was assessed at baseline and endline. ANCOVA and linear regression models were used to assess group differences in HCC and to examine the risk factors associated with HCC, respectively. At enrollment, mean HCC was 28.8 ± 43.9 pg/mg. In models adjusted for age at enrollment, health district, and baseline HCC there was no overall effect of the interventions on endline HCC and change in HCC. When controlling for additional predetermined covariates, there was a marginally significant effect on change in HCC (p = 0.075) with a slightly lower reduction of HCC in TZ compared to PZ (mean change (95% CI): -4.6 (-7.0; -2.3) vs. -9.4 (-11.7; -7.0) pg/mg; p = 0.053). At baseline, consumption of iron rich foods was negatively associated with HCC, whereas AGP (α1-acid glycoprotein) levels, elevated AGP and C-reactive protein and high soluble transferrin receptor were positively associated with HCC. In young Laotian children, MNP, PZ and TZ had no impact on HCC. The marginal difference in change in HCC between the PZ and TZ groups was too small to be considered of health significance.

Hair cortisol concentration in mothers and their children: roles of maternal sensitivity and child symptoms of attention-deficit/hyperactivity disorder

Associations between mothers' and children's cortisol secretion parameters are well established. According to the bio-behavioral synchrony model, these associations reflect influences of the mother-child relationship, the child's social adjustment, and might also reflect shared genetic dispositions. From the bio-behavioral synchrony model, we predicted a stronger mother-child hair cortisol concentration (HCC) link in mothers showing highly adequate (compared to those showing less adequate) parenting behaviors and in children showing low (compared to those showing high) ADHD symptoms. From a genetic perspective, no such moderator effects, or a stronger mother-child HCC link in children with high ADHD symptoms, can be expected. The study sample consisted of 111 4-5-year-old children (64 of whom screened positive for increased ADHD symptoms) and their mothers. ADHD symptoms were assessed by a clinical interview and parent and teacher questionnaires. Maternal sensitive/responsive parenting behavior was assessed by an at-home behavior observation procedure. In mothers and children, HCC in the most proximal 3-cm scalp hair segment was analyzed using luminescence immunoassay. Overall HCCs of mothers and their children correlated significantly. Maternal sensitivity/responsiveness and child ADHD symptoms proved to be significant moderator variables of this association: High maternal sensitivity/responsiveness and low ADHD symptoms of the child were associated with a stronger mother-child link in HCC. The findings are in line with the bio-behavioral synchrony model in the mother-child relationship, and are less compatible with a genetic perspective. The results might hint at environmental events influencing the development of stress axis functioning in subgroups of preschoolers with high ADHD symptoms.

Newborn infants' hair cortisol levels reflect chronic maternal stress during pregnancy

Cortisol obtained from hair samples represents a retrospective biomarker of chronic stress experienced by the subject in previous months. Although hair cortisol levels have been used to study the relationship between maternal and neonatal stress levels in primates, this has not yet been performed in humans using a longitudinal design and focusing specifically on this association. Therefore, the objective of this study was to determine whether a relationship existed between maternal psychological stress and hair cortisol levels during pregnancy and postpartum, and neonatal hair cortisol levels. The sample consisted of 80 pregnant women and their 80 newborn infants. We conducted a longitudinal assessment of hair cortisol levels, psychological stress, anxiety, and depression in the three trimesters of pregnancy and postpartum. After childbirth, neonatal hair cortisol levels were also measured. We found that maternal hair cortisol levels in the first trimester negatively predicted neonatal hair cortisol levels. Perceived stress in the third trimester of pregnancy also predicted lower neonatal cortisol, whereas pregnancy-specific stress in the same trimester had a positive relation with neonatal cortisol. Cortisol is essential for embryonic and fetal development; consequently, if fetal synthesis of cortisol is affected by high maternal cortisol levels, such development could be impaired.