Symposium
Chair: Megan R. Gunnar
Discussant: Megan R. Gunnar
Research on animals documents the long-term impact of early neglect on the reactivity of limbic-hypothalamic-pituitary-adrenocortical (LHPA) axis. On the whole, rodent and monkey infants deprived of maternal care or exposed to less than optimal care develop a more stress-reactive LHPA axis. Increased LHPA axis responsivity corresponds to altered reactivity in other stress-sensitive CNS systems and to heightened fearfulness and increased risk of later drug/alcohol abuse and aging-related physical/mental disorders.This symposium brings together research that begins to examine the applicability of these animal models to early human development. Two papers deal with what is known about the correlation between quality of care and LHPA axis activity in young children growing up in adequate care environments. In both of these papers, one focus will be on interactions between quality of care and temperament, showing that both temperamentally anxious and undercontrolled children are the most vulnerable to heightened LHPA axis responding as care quality is reduced. The first paper deals with care quality within the family; the second with care quality within the daycare context. The second two papers shift us from adequate to maltreating/neglecting care contexts. In the third paper, year-old infants who meet criteria of severe neglect are compared to infants in high risk (but not neglecting) and low risk family contexts. Although most animal models suggest that neglect should heightened stress reactivity, the results of this study demonstrate a blunting of LHPA, autonomic, and behavioral indices of reactivity for the Neglected infants. Some, but not all, neglected/maltreated children develop the syndrome of Psychosocial Dwarfism (PSD). This syndrome, believed to be produced by chronic elevations in LHPA axis activity, is defined by low pituitary production of growth hormone (GH) and cell-insensitivity to GH. These neuroendocrine abnormalities revert once the child has been removed from the maltreating environment. The fourth paper demonstrates that children with PSD do exhibit altered LHPA axis functioning consistent with the model of hyper-responsivity in response to neglect.The discussant will provide a brief introduction to the history of research in this area and the physiology under examination. Following the papers, the discussant will help identify the consistencies and inconsistencies both among the data presented in the symposium and between the data presented and the animal research findings. Overall, the goal of the symposium is to serve as a tutorial for behavioral development researchers interested in expanding their understanding of early experiences to include physiological processes. In addition, as the symposium brings together a developmental psychologist, developmental psychobiologist, pediatric neurologist, and pediatric endocrinologist, the symposium serves as a model of the type of inter-disciplinary approach needed to address questions about the psychobiology of early experience.
Details of individual items:
paper
Attachment research has shown the importance of the quality of infant-mother attachment for the development of social-emotional competence. A secure attachment pattern has been interpreted as adaptive for individual development and as an effective behavioral strategy for coping with emotionally stressful situations. A secure attachment relationship is based on the experience with a sensitive, responsive caregiver who may serve as an external organizer for the infant when faced with emotional challenges. Studies adopting a psychobiological perspective have investigated the regulatory function of attachment quality also on a physiological level using measures of the stress-sensitive limbic-hypothalamic-pituitary-adrenocortical (LHPA) system. In these studies, because securely attached infants are able to perform adaptive behavioral strategies only small increases in cortisol, the LHPA hormone, have been predicted. In contrast, the restricted ability for emotion regulation on the behavioral level in insecurely attached infants has lead to predictions of greater cortisol responses to stressors. Findings from two longitudinal studies will be presented demonstrating the role of attachment processes for biobehavioral regulation during early childhood. (All results described as significant were p <.05 or better). In the first study (Regensburg Longitudinal Study III) 41 infants together with their mothers were observed during play at 3, 6 and 9 months of age. As differences in attachment quality cannot be assessed until the end of the first year, maternal sensitivity was examined. Age-specific patterns of relation between maternal sensitivity and infant behavioral organization were found indicating contextual dependence of infant behavior at 3 months and experience-related behavioral function at 9 months. An association between maternal sensitivity and adrenocortical function during the play was demonstrated at 3 and 6 months. Elevations in cortisol over the play sessions were most frequently observed in infants of highly insensitive mothers. The findings demonstrates that insensitive caregiving may activate the LHPA axis in infants even the under seemingly low stress conditions of parent-infant play. In the second study (Regensburg Longitudinal Study IV) 106 infants were observed during the Strange Situation at 12 months to assess quality of attachment. At the age of 22 months 76 of these infants were observed again during a problem-solving task to assess behavioral coping strategies and attachment-exploration balance. Saliva samples were collected at both ages for cortisol determination. In line with previous findings, adrenocortical activation during the Strange Situation at 12 months was most prominent for infants with insecure attachment, particularly if they were also high in behavioral inhibition. Behaviorally inhibited infants with secure attachment did not demonstrate increases in cortisol. This demonstrates the capacity of secure attachment to buffer physiological stress responses for children with seemingly more vulnerable temperamental dispositions. At 22 months incompetent problem solving behavior was associated with increases in cortisol. Moreover, attachment security was associated with different patterns of coping strategies that appeared to modify LHPA activation for children of different temperaments. The findings support the importance of attachment security and sensitive caregiving for psychobiological organization in response to challenging/stressful situations in early childhood.
paper
Full day childcare can be viewed as a normative challenge for young children. Similar to the parent-child context, we expect that the quality of care will determine whether children meet the challenge of childcare without experiencing elevations in stress hormones. We also anticipate that children with difficult behavioral styles (low self control, high anger/aggression) will be most prone to elevate stress hormones in childcare settings because they will be the most likely to be involved in stressful social encounters. Three studies will be briefly reviewed. All results described as significant had p values of .05 or better. Study 1 included 70 children aged 3 to 9 years attending full-day, center-based childcare. Salivary cortisol concentrations were assessed twice daily (10.30 am / 3.30 pm) for 2 days at home and childcare. Teachers and parents completed Rothbart's Child Behavior Questionnaire (CBQ). Regarding cortisol, there was a significant time-of-day by context interaction. At home, cortisol decreased over the day reflecting the normal, circadian rhythm in this neuroendocrine system. At childcare, cortisol rose over the day, especially for the younger (age 3 and 4) children. Across all ages, angry/aggressive/undercontrolled children exhibited the largest increases in cortisol over the day at childcare. Study 2 examined 3-5 year olds at 2 full-day, center-based childcare programs that differed in quality (ECCERs and Arnett quality measures) from good to excellent. Twenty days of 10 a.m. and 3 p.m. cortisol were obtained and averaged. The results showed a significant interaction between centers and the rise in cortisol over the day, with the center scoring lower in quality (i.e., good range) having children who experienced the larger increases in cortisol than those observed at the center scoring higher in quality (i.e., excellent range). Again, children who were more angry/aggressive showed the greatest evidence of cortisol responsivity at childcare. Study 3: In order to extend the analysis of quality, we examined 21 family-based full-day childcare sites with one target child at each site. The ORCE (NICHD) was used to assess family-based childcare quality which ranged, again, from good to excellent. Two days of 10 a.m. and 3 p.m. cortisol sampling was completed at home and at childcare. Home cortisol levels decreased over the day and were uncorrelated with childcare quality or temperament. Childcare cortisol levels rose over the day, with the rise correlating inversely with childcare quality. Again, larger increases were noted for aggressive, under-controlled children, however, this was only true in the sites scoring below the median on the quality indices (i.e., in the good range). In the higher quality sites (i.e., excellent range), regardless of temperament children at home and childcare decreased cortisol levels over the day. These studies indicate that young children, particularly those with poorly regulated, more aggressive behavior patterns, are vulnerable to producing rises in cortisol at childcare. However, excellent quality of care can prevent hormonal stress responses even for children with more difficult temperaments. As in the studies of parents and young children, quality of care appears to regulate the reactivity of this stress-sensitive neuroendocrine system.
paper
The neurobiology of infant neglect remains largely unexplored despite increasing recognition of the importance of early biological adaptations to adverse life events. Animal and preliminary human studies suggest that ontogenetically immature, rapidly developing systems are the ones most susceptible to psychological and physical trauma sustained during infancy. The limbic-hypothalamic-pituitary-adrenal (LHPA) axis and autonomic nervous system (ANS) are strongly implicated in the pathogenesis of age-related morbidity and mortality following early deprivation/neglect. We predicted that infants reared in more stressful rearing environments would exhibit altered biologic (LHPA & ANS cardiac function) and behavioral stress reactivity and regulation compared to infants reared in less stressful rearing environments. Participants were 36 one-year-old mother-infant dyads recruited from well-baby & high risk clinics, and the emergency department of a midwest inner city children's hospital. Based on inclusion criteria, a Neglect Risk Factor Score (NRFS) was used to assign participants to Neglected (n 3D 14; NRFS3D -26.14 B1 3.4); High Risk (n3D 13; NRFS3D -0.14 B1 1.87); and Low Risk (n 3D 9; NRFS3D +10) groups (p<0.0001). Diurnal salivary cortisols were collected and assayed by standard radioimmunoassay. Autonomic cardiac activity was assayed by impedance cardiography using a modification of the Sherwood method. Baseline measures of heart rate, pre-ejection period, and respiratory sinus arrhythmia were compared to response measures to 2 mild stressors (4 minute maternal separation; exposure to a 30 sec sick infant cry). Infants and mothers were observed and scored during the laboratory assessment by observers trained to reliability. The HOME inventory and Bayley tests were also completed and mothers filled out the Beck Depression Inventory II to assess maternal psychopathology. All significant results reported below are p<0.05 or better. The HOME significantly predicted risk groups. Mothers from Neglected and High Risk dyads were significantly more likely to be depressed than mothers from the Low Risk group. Bayley scores for Neglected infants were lower than for the other infants. Compared to the Low Risk group, Neglected infants exhibited a more constricted behavioral repertoire, with markedly decreased duration of cry to maternal separation and a shorter behavioral arrest to hearing a sick infant cry. This constricted response pattern was reflected in both cortisol diurnal rhythms and in autonomic reactivity. Neglect status was associated with a significant blunting of the daily cortisol rhythm (B5g/dL decrease over the days was .04, .2, .4 for the Neglected, High Risk, and Low Risk groups, respectively). Sympathetic activation in Neglected infants was significantly blunted to maternal separation and reunion (separation 0%; reunion +2.3%) compared to Low Risk infants (+7.3% & -10.9%) or High Risk infants (+3.6% & -4.4%). Although theoretically, early stress effects on neurobiology are due to a heightening of stress reactivity during periods of neglect, this is not what we observed. Our findings of a blunted cortisol circadian rhythm are similar to reports on institutionalized Romanian infants (Carlson & Earls, 1997) and in depressed, maltreated school-aged children (Kaufman et al., 1991; Hart et al., 1997). These effects suggest that alterations in our theories of early stress may be needed.
paper
Fast rates of skeletal and brain growth are hallmarks of mammalian postnatal life. Nevertheless, under conditions of extreme demand/stress, one can hypothesize that growth may be categorized as 'nonessential' allowing energy to be re-channeled to immediate adaptation/survival tasks. Numerous animal studies have shown that early life stressors can produce profound alterations in the growth that impact adult functioning. In humans, pediatricians observe a syndrome of growth failure associated with chaotic home environments/neglect. The syndrome is called Failure to Thrive (FTT) in infants and Psychosocial Dwarfism (PSD) in children older than 3, a distinction that reflects the infant's greater dependence on parental care for its nutrition. Two neuroendocrine systems may be in producing growth failure in these children: 1) the Growth Hormone (GH) axis and 2) the limbic-hypothalamic-pituitary-adrenal (LHPA) axis. GH axis modulation involves two hypothalamic peptides: Growth Hormone Releasing Hormone (GHRH) which promotes pituitary GH production and somatostatin which inhibits it. Children with PSD have low GH secretion in response to provocative challenge. The low GH levels in children with PSD appear to be induced primarily by psychological stress, since the GH levels and growth revert to normal upon removal from the stressful, neglectful home environment. From human and animal studies we know that acute administration of cortisol, produced by the LHPA axis, suppresses pituitary GH secretion. In addition, administration of the brain hormone that initiates the LHPA response, CRH, causes an increase of somatostatin thereby inhibiting GH secretion. Thus, in PSD alterations in LHPA functioning that produce greater or more prolonged elevations in cortisol could be involved in suppressing GH and thus growth. We have started a study of PSD compared to normally growing short stature children in order to examine LHPA alterations in PSD. Subjects were matched for bone age and sex (n3D11 per group). Three aspects of the stress hormone axis are reported here: 1) basal cortisol secretion during evening hours, 2) cortisol and pituitary response to low blood glucose (insulin-induced hypoglycemia), and 3) the ability to 'turn off' the brain-pituitary activation using an infusion of synthetic cortisol (Solu-Cortef). Although evening basal cortisol levels did not distinguish the PSD population from normally growing children, the insulin and synthetic cortisol challenges point to an impaired ability to suppress the stress response once initiated. Specifically, compared to normal short stature children, PSD patients failed to effectively 'turn off' the ACTH and cortisol response to insulin hypoglycemia (p < 0.05), and to inhibit ACTH secretion in response to Solu-Cortef infusion (p< 0.01). Taken together, these data suggests that children with growth failure associated with psychosocial stress/neglect show LHPA axis alterations that would result in prolonged elevations in stress hormones relative to controls following stressor activation. These data supports the hypothesis that, in children with PSD, sustained elevations of adrenal stress hormones and hypothalamic activating hormones maintain a hormonal environment that contributes to their growth retardation. Sponsored by DA02265 and M01RR00042.