Examining stress reactivity in neonates: relations between cortisol and behavior

Development of negative and positive emotionality in irritable and nonirritable neonates

OBJECTIVE

The current study compares the development of negative and positive emotionality of irritable and nonirritable neonates.

BACKGROUND

Research indicates that the first few months of life are marked by decreases in negative emotionality and increases in positive emotionality.

METHODS

The Neonatal Behavioural Assessment Scale (NBAS) was administered twice to 111 neonates at 3 and 4 weeks of age to select a sample of irritable neonates and a comparison group of nonirritable neonates. Mothers completed assessments of negative and positive emotionality at 1, 2, 4, and 9 months of age.

RESULTS

Both irritable and nonirritable neonates demonstrate a significant decrease in frustration and a significant increase in positive emotionality from 2 to 4 months of age. Irritable neonates also demonstrate a significant decrease in negative emotionality from 4 to 9 months of age. Both irritable and nonirritable neonates demonstrate considerable stability in negative and positive emotionality.

CONCLUSION

Implications of these results for parent education and early intervention are discussed.

Objective Assessment of Temperament in Temperamentally Vulnerable Children: Role in the Studies on Their Stress Levels

Under conditions of suboptimal parental care, children with specific temperamental features have been shown to be especially vulnerable to the effects of stress. Most studies of temperamentally vulnerable children have been conducted using parental questionnaires, which are unfortunately not completely objective. An alternative approach, the use of objective methods for assessing temperament in childhood, can and should be used to study the impact of poor parenting quality on children's stress levels, an important factor in child development. Although studies using such objective methods exist, they are quite rare. A PubMed search identified twelve articles reviewed here. Existing data indicate that, in general, higher basal cortisol and cortisol stress response are associated with "reactive" temperament: shyness, fearfulness, behavioral inhibition, and negative affectivity. Furthermore, child temperament interacts with the quality of parental care to predict cortisol levels in early childhood. Accordingly, in the context of inadequate parental care, temperamentally vulnerable children with "reactive" temperaments are particularly at risk for negative effects of stress. Studies of stress-by-parental-care-interactions are essential for preventing long-term mental problems and problems with physical health that could occur in temperamentally vulnerable children who receive suboptimal parental care.

Birth signalling hormones and the developmental consequences of caesarean delivery

Rates of delivery by caesarean section (CS) are increasing around the globe and, although several epidemiological associations have already been observed between CS and health outcomes in later life, more are sure to be discovered as this practice continues to gain popularity. The components of vaginal delivery that protect offspring from the negative consequences of CS delivery in later life are currently unknown, although much attention to date has focused on differences in microbial colonisation. Here, we present the case that differing hormonal experiences at birth may also contribute to the neurodevelopmental consequences of CS delivery. Levels of each of the 'birth signalling hormones' (oxytocin, arginine vasopressin, epinephrine, norepinephrine and the glucocorticoids) are lower following CS compared to vaginal delivery, and there is substantial evidence for each that manipulations in early life results in long-term neurodevelopmental consequences. We draw from the research traditions of neuroendocrinology and developmental psychobiology to suggest that the perinatal period is a sensitive period, during which hormones achieve organisational effects. Furthermore, there is much to be learned from research on developmental programming by early-life stress that may inform research on CS, as a result of shared neuroendocrine mechanisms at work. We compare and contrast the effects of early-life stress with those of CS delivery and propose new avenues of research based on the links between the two bodies of literature. The research conducted to date suggests that the differences in hormone signalling seen in CS neonates may produce long-term neurodevelopmental consequences.

Neonatal Negative Emotionality and the Child Behavior Checklist-Dysregulation Profile (CBCL-DP) in middle childhood

Objective: Determine whether an association exists between neonatal negative emotionality and childhood emotional dysregulation. Background: The Child Behaviour Checklist-Dysregulation Profile (CBCL-DP) has been used as a measure of emotional dysregulation in childhood. Although there is now good evidence that the CBCL-DP predicts later psychopathology, little is known about what factors predict elevations on the CBCL-DP. Methods: 30 mother-child dyads who previously participated in a study of neonatal temperament were recruited to a follow-up study of emotional dysregulation during middle childhood. The Neonatal Behaviour Assessment Scale (NBAS) and the Infant Characteristics Questionnaire (ICQ) were utilised as observer and maternal measures of neonatal negative emotionality, respectively. Maternal post-partum depression was also measured during the neonatal period using the Edinburgh Post-Partum Depression Scale (EPDS). The Child Behaviour Checklist-Dysregulation Profile (CBCL-DP) was used as a measure of childhood emotional dysregulation. Results: The ICQ fussy-difficult scale was significantly correlated with the CBCL-DP score (r = .46, p = .010), and this correlation remained significant after controlling for maternal EPDS score (CBCL-DP r = .51, p = .01). The NBAS irritability score was not associated with the CBCL-DP score. Conclusions: This association provides preliminary results that neonates rated as having high negative emotionality may indeed experience chronic difficulties with emotional dysregulation.

Behavioral and cortisol responses to stress in newborn infants: Effects of mode of delivery

Suboptimal birth characteristics have been associated with altered reactivity to stress in infants. However, previous studies have not controlled for mode of delivery, which may influence the neonatal onset of stress responses. The present study assessed stress-related behavior and salivary cortisol before and after an inoculation at two hours after birth, and compared infants born through VD (N=70) and elective CS (N=72). The results indicated that overall stress behavior and body movements were increased immediately after inoculation in infants born through CS compared to VD. Infants born through CS did not show significant cortisol increases following inoculation and their overall cortisol reactivity (i.e., AUC_G) was lower compared to infants born through VD. However, unexpectedly, cortisol levels in infants born through VD were highest before inoculation and subsequently decreased. Cortisol was significantly related to behavior in both groups, but in opposite directions. These results support the view that mode of delivery influences neonatal stress reactivity, although future studies should try to disentangle the effects of mode of delivery and related variables.

Prenatal predictors of infant self-regulation: the contributions of placental DNA methylation of NR3C1 and neuroendocrine activity

We examined whether placental DNA methylation of the glucocorticoid receptor gene, NR3C1 was associated with self-regulation and neuroendocrine responses to a social stressor in infancy. Placenta samples were obtained at birth and mothers and their infants (n = 128) participated in the still-face paradigm when infants were 5 months old. Infant self-regulation following the still-face episode was coded and pre-stress cortisol and cortisol reactivity was assessed in response to the still-face paradigm. A factor analysis of NR3C1 CpG sites revealed two factors: one for CpG sites 1–4 and the other for sites 5–13. DNA methylation of the factor comprising NR3C1 CpG sites 5–13 was related to greater cortisol reactivity and infant self-regulation, but cortisol reactivity was not associated with infant self-regulation. The results reveal that prenatal epigenetic processes may explain part of the development of infant self-regulation.

Is that me or my twin? Lack of self-face recognition advantage in identical twins

Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated. One's own face is the most distinctive feature of the bodily self, and people typically show a clear advantage in recognizing their own face even more than other very familiar identities. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing. Herein we examined the ability of monozygotic twins to distinguish their own face from the face of their co-twin and of a highly familiar individual. Results show that twins equally recognize their own face and their twin's face. This lack of self-face advantage was negatively predicted by how much they felt physically similar to their co-twin and by their anxious or avoidant attachment style. We speculate that in monozygotic twins, the visual representation of the self-face overlaps with that of the co-twin. Thus, to distinguish the self from the co-twin, monozygotic twins have to rely much more than control participants on the multisensory integration processes upon which the sense of bodily self is based. Moreover, in keeping with the notion that attachment style influences perception of self and significant others, we propose that the observed self/co-twin confusion may depend upon insecure attachment.

Interparental aggression and infant patterns of adrenocortical and behavioral stress responses

Drawing on emotional security theory, this study examined linkages between interparental aggression, infant self-regulatory behaviors, and patterns of physiological and behavioral stress responses in a diverse sample of 735 infants residing in predominately low-income, non-metropolitan communities. Latent profile analysis revealed four classes of adrenocortical and behavioral stress-response patterns at 7 months of age, using assessments of behavioral and cortisol reactivity to an emotion eliciting challenge, as well as global ratings of the child's negative affect and basal cortisol levels. The addition of covariates within the latent profile model suggested that children with more violence in the home and children who used less caregiver-oriented regulation strategies were more likely to exhibit a pattern of high cortisol reactivity with moderate signs of distress rather than the average stress response, suggesting possible patterns of adaptation in violent households.

Biomarkers of epidermal innate immunity in premature and full-term infants

Epidermal innate immunity is a complex process involving a balance of pro- and anti-inflammatory cytokines, structural proteins, and specific antigen presenting cells occurring against a background of neuroendocrine modulators such as cortisol. In this study, a multiplex array system was used to simultaneously determine multiple molecular factors critical for development of epidermal innate immune function from the skin surface of premature and term infants, healthy adults, and vernix caseosa. Samples were analyzed for Keratin 1,10,11, Keratin 6, involucrin, albumin, fibronectin and cortisol, and cytokines IL-1, TNFalpha, IL-6, IL-8, MCP1, IP10, IFNgamma, and IL-1 receptor antagonist. Keratin 1,10,11 was decreased and involucrin was increased in infants versus adults. All infants had elevated IL1alpha and reduced TNFalpha versus adults. IL-6, IL-8, and MCP1 were significantly increased in premature versus term infants and adults. Skin surface cortisol and albumin were significantly elevated in premature infants. The biomarker profile in premature infants was unique with differences in structural proteins, albumin, and cytokines IL-6, IL-1beta, IL-8, and MCP1. The higher infant IL1alpha may be associated with skin barrier maturation. The significant elevations in skin surface cortisol for preterm infants may reflect a neuroendocrine response to the stress of premature birth.

Perceived maternal stress during pregnancy and its relation to infant stress reactivity at 2 days and 10 months of postnatal life

BACKGROUND

Although the negative impact of maternal stress during pregnancy on stress reactivity in offspring is well documented in nonhuman animals, we know little about these relations in humans and their lasting effects.

AIM

The authors examined the relation between perceived maternal stress during pregnancy and stability of infant stress reactivity across the first year of postnatal life in humans.

STUDY DESIGN

Perceived maternal stress during pregnancy was measured in the immediate postpartum period and again at 10 months after delivery in 84 mothers and examined in relation to behavioral and neuroendocrine stress reactivity measures in their healthy, full-term infants.

OUTCOME MEASURES

Salivary cortisol was collected between 24 to 48 hours of postnatal life in response to a heel stick and again at 10 months of age in response to a toy removal task in the same sample of infants. Behavioral reactivity was coded from direct observation during the toy removal task.

RESULTS

Perceived maternal stress during pregnancy and neonatal cortisol reactivity each remained stable across the first 10 months of postnatal life. Maternal stress during pregnancy predicted infant cortisol reactivity at 2 days and 10 months after birth as well as behavioral reactivity at 10 months. Neonatal cortisol reactivity predicted 10-month behavioral reactivity.

CONCLUSION

These preliminary findings suggest that maternal stress during pregnancy may negatively affect neonatal stress reactivity within 24 to 48 hours after birth, and these influences may persist through the first year of postnatal life.

Childbirth complications affect young infants' behavior

BACKGROUND

The process of childbirth and its complications have been related to the newborn's condition and to development at later ages. In this study, we examine how mode of delivery and delivery complications are related to the behavior and cortisol reactivity of infants during the first 2 months.

METHODS

Delivery factors (i.e. mode, duration, fetal heart function, and 5-min Apgar score) were determined in 116 healthy, term, firstborn infants. The infants' behavioral and cortisol reactivity to stressors were assessed during a physical examination at 11 days and an inoculation at 2 months. Daily behavior at 6 weeks was followed by means of a four-day parental diary.

RESULTS

Indicators of a more stressful delivery were linked to more crying/fussing in the infant and to more difficulties in regulating the infants' behavior (i.e., more unsoothability and longer crying bouts). Specific delivery complications rather than mode of delivery were linked to infants' behavior. No significant associations however, were found between childbirth and the infants' cortisol reactivity to a physical examination and an inoculation.

CONCLUSIONS

Childbirth complications, even when mild, can apparently affect early infant behavior. These effects extend over different types of situations, and last at least until the age of 2 months, and should be taken into account in studies on infant behavior. Earlier findings of relations between childbirth complications and infant cortisol reactivity could not be replicated in this study, possibly due to the confounding effect of parity, and to the important intra-individual variability present in the infants' cortisol.

Parsing the relations between SES and stress reactivity: Examining individual differences in neonatal stress response

In an effort to further delineate the reported relations between socioeconomic status (SES) and stress reactivity in children, associations between three domains of perinatal risk: socio-demographic, obstetrical complications, and maternal psychological factors during the perinatal period, and cortisol and behavioral reactivity were examined in 100 healthy African American neonates whose families resided in low-income environments. Behavioral and cortisol response to a heel stick and the Neonatal Behavioral Assessment Scale (NBAS) was measured within the first 2 days of life. Significant associations were found between socio-demographic risk, obstetrical complications, and maternal psychological factors and neonatal behavior and cortisol in the context of the NBAS; few significant associations were found in the context of the heel stick. Greater magnitude of perinatal risk was associated with both higher and lower than average neonatal stress reactivity. The results provide preliminary data on the types of perinatal experiences that may have significant effects on stress reactivity in humans, especially in the context of families living in poverty. Application of these data to the hypothesis that prenatal stress results in programming of the fetal/neonatal stress response system is discussed.

Infant emotional and cortisol responses to goal blockage

This study examined the relation of infant emotional responses of anger and sadness to cortisol response in 2 goal blockage situations. One goal blockage with 4-month-old infants (N = 56) involved a contingency learning procedure where infants' learned response was no longer effective in reinstating an event. The other goal blockage with 6-month-old infants (N = 84) involved the still face procedure where infants' reactions to their mothers' lack of responsivity were not effective in reestablishing interaction. For both blockages, sadness was related to cortisol response, though anger was not--the greater the sadness, the higher the cortisol response. This differential relation is consistent with other evidence indicating the more positive role of anger as opposed to sadness in overcoming an obstacle.