Roger Mills-Koonce

Salivary cortisol mediates effects of poverty and parenting on executive functions in early childhood.

In a predominantly low-income population-based longitudinal sample of 1,292 children followed from birth, higher level of salivary cortisol assessed at ages 7, 15, and 24 months was uniquely associated with lower executive function ability and to a lesser extent IQ at age 3 years. Measures of positive and negative aspects of parenting and household risk were also uniquely related to both executive functions and IQ. The effect of positive parenting on executive functions was partially mediated through cortisol. Typical or resting level of cortisol was increased in African American relative to White participants. In combination with positive and negative parenting and household risk, cortisol mediated effects of income-to-need, maternal education, and African American ethnicity on child cognitive ability.

The effects of socioeconomic status, race, and parenting on language development in early childhood.

The authors examined the associations between socioeconomic status (SES), race, maternal sensitivity, and maternal negative-intrusive behaviors and language development in a sample selected to reduce the typical confound between race and SES (n = 146). Mother-child interactions were observed at 12 and 24 months (coded by randomly assigned African American and European American coders); language abilities were assessed at 18, 24, 30, and 36 months. For receptive language, race was associated with ability level, and maternal sensitivity and negative-intrusive parenting were related to rate of growth. For expressive communication, race, SES, and maternal sensitivity were associated with rate of growth; race moderated the association between negative-intrusive parenting and rate of growth such that the relation was weaker for African American than for European American children. The results highlight the importance of sensitive parenting and suggest that the association between negative-intrusive parenting and language development may depend upon family context. Future work is needed concerning the race differences found, including examining associations with other demographic factors and variations in language input experienced by children, using culturally and racially validated indices of language development.

Allostasis and allostatic load in the context of poverty in early childhood.

This paper examined the relation of early environmental adversity associated with poverty to child resting or basal level of cortisol in a prospective longitudinal sample of 1135 children seen at 7, 15, 24, 35, and 48 months of age. We found main effects for poor housing quality, African American ethnicity, and low positive caregiving behavior in which each was uniquely associated with an overall higher level of cortisol from age 7 to 48 months. We also found that two aspects of the early environment in the context of poverty, adult exits from the home and perceived economic insufficiency, were related to salivary cortisol in a time-dependent manner. The effect for the first of these, exits from the home, was consistent with the principle of allostatic load in which the effects of adversity on stress physiology accumulate over time. The effect for perceived economic insufficiency was one in which insufficiency was associated with higher levels of cortisol in infancy but with a typical but steeper decline in cortisol with age at subsequent time points.

Maternal and Child Contributions to Cortisol Response to Emotional Arousal in Young Children from Low-Income, Rural Communities.

Relations of maternal and child characteristics to child cortisol reactivity to and recovery from emotional arousal were examined prospectively at approximately 7 months of age (infancy) and then again at approximately 15 months of age (toddlerhood). The sample was diverse and population based (N = 1,292 mother-infant dyads) and included families from predominantly low-income, rural communities. Maternal behavior, family income-to-need ratio and social advantage, and child temperament, attention, and mental development were assessed, and childrens saliva was sampled before and after standardized procedures designed to elicit emotional arousal. Maternal engagement in infancy was associated with greater cortisol reactivity at the infancy assessment and with reduced overall cortisol level at the toddler assessment. Also at the toddler assessment, child attention, mental development, and temperamental distress to novelty were associated with increased cortisol reactivity and regulation, whereas temperamental distress to limitations and African American ethnicity were associated with reduced cortisol reactivity. Findings are consistent with prior work linking early caregiving to the development of the hypothalamic-pituitary-adrenal axis stress response system and with a conceptual model in which developing temperament is characterized by the interplay of emotional reactivity and the emergence of the ability to effortfully regulate this reactivity using attention.

Cumulative effects of early poverty on cortisol in young children: Moderation by autonomic nervous system activity

The relation of the cumulative experience of poverty in infancy and early childhood to child cortisol at age 48 months was examined in a prospective longitudinal sample of children and families (N=1292) in predominantly low-income and rural communities in two distinct regions of the United States. Families were seen in the home for data collection and cumulative experience of poverty was indexed by parent reported income-to-need ratio and household chaos measures collected between child ages 2 months and 48 months. For the analysis presented here, three saliva samples were also collected over an approximate 90 min interval at child age 48 months and were assayed for cortisol. ECG data were also collected during a resting period and during the administration of a mildly challenging battery of cognitive tasks. Mixed model analysis indicated that child cortisol at 48 months decreased significantly over the sampling time period and that cumulative time in poverty (number of years income-to-need less than or equal to 1) and cumulative household chaos were significantly related to a flatter trajectory for cortisol change and to an overall higher level of cortisol, respectively. Findings also indicated that respiratory sinus arrhythmia derived from the ECG data moderated the association between household chaos and child cortisol and that increase in respiratory sinus arrhythmia during the cognitive task was associated with an overall lower level of cortisol at 48 months.

Observed parenting behaviors interact with a polymorphism of the brain-derived neurotrophic factor gene to predict the emergence of oppositional defiant and callous–unemotional behaviors at age 3 years

Using the Durham Child Health and Development Study, this study (N = 171) tested whether observed parenting behaviors in infancy (6 and 12 months) and toddlerhood/preschool (24 and 36 months) interacted with a child polymorphism of the brain-derived neurotrophic factor gene to predict oppositional defiant disorder (ODD) and callous-unemotional (CU) behaviors at age 3 years. Child genotype interacted with observed harsh and intrusive (but not sensitive) parenting to predict ODD and CU behaviors. Harsh-intrusive parenting was more strongly associated with ODD and CU for children with a methionine allele of the brain-derived neurotrophic factor gene. CU behaviors were uniquely predicted by harsh-intrusive parenting in infancy, whereas ODD behaviors were predicted by harsh-intrusive parenting in both infancy and toddlerhood/preschool. The results are discussed from the perspective of the contributions of caregiving behaviors as contributing to distinct aspects of early onset disruptive behavior.

Early childcare, executive functioning, and the moderating role of early stress physiology.

Intervention studies indicate that childrens childcare experiences can be leveraged to support the development of executive functioning (EF). The role of more normative childcare experiences is less clear. Increasingly, theory and empirical work suggest that individual differences in childrens physiological stress systems may be associated with meaningful differences in the way they experience these early environments. Using data from a large population-based sample of predominantly low-income rural families, we tested the degree to which childrens childcare experiences--quantity, quality, and type--in the first 3 years of life predicted emerging EF. Moreover, we examined whether these effects varied as a function of childrens basal cortisol levels in infancy and toddlerhood--an indicator of hypothalamic pituitary adrenal (HPA) axis stress physiology. Our results showed that higher quality care predicted more effective EF at 48 months, irrespective of quantity or type. This relation did not vary as a function of childrens early cortisol levels. Attending greater hours of care per week was also related to EF; however--consistent with theory--the positive association between spending more time in childcare and more positive EF extended only to children with low levels of basal cortisol at 7 or 24 months of age. Attending center-based care was unassociated with EF.

Respiratory sinus arrhythmia and heart period in infancy as correlates of later oppositional defiant and callous-unemotional behaviors

Extant literature suggests that oppositional defiant disorder (ODD) and callous-unemotional (CU) behaviors in childhood and adolescence are associated with distinct patterns of psychophysiological functioning, and that individual differences in these patterns have implications for developmental pathways to disorder. Very little is known about the associations between psychophysiological functioning in infancy and later ODD and CU behaviors. This study examined associations between basal autonomic nervous system (ANS) functioning in infancy and ODD and CU behaviors in later childhood. Using longitudinal heart period (HP) and respiratory sinus arrhythmia (RSA) data from the Durham Child Health and Development Study (N = 206), the current study tested associations within a structural equation modeling framework, between continuous measures of HP and RSA across the first 2 years of life, and later ODD and CU behaviors at first grade. Results indicate that ODD and CU behaviors in childhood are associated with lower baseline RSA, but not HP, across infancy. The implications of these findings for developmental models of ODD and CU behaviors are discussed.

Psychobiological influences on maternal sensitivity in the context of adversity

This study evaluated prospective longitudinal relations among an index of poverty-related cumulative risk, maternal salivary cortisol, child negative affect, and maternal sensitivity across the first 2 postpartum years. Participants included 1,180 biological mothers residing in rural and predominantly low-income communities in the United States. Multilevel growth curve analyses indicated that an index of cumulative risk was positively associated with maternal cortisol across the postpartum (study visits occurring at approximately 7, 15, and 24 months postpartum) over and above effects for African American ethnicity, time of day of saliva collection, age, parity status, having given birth to another child, contraceptive use, tobacco smoking, body mass index, and breastfeeding. Consistent with a psychobiological theory of mothering, maternal salivary cortisol was negatively associated with maternal sensitivity observed during parent-child interactions across the first 2 postpartum years over and above effects for poverty-related cumulative risk, child negative affect, as well as a large number of covariates associated with cortisol and maternal sensitivity. Child negative affect expressed during parent-child interactions was negatively associated with observed maternal sensitivity at late (24 months) but not early time points of observation (7 months) and cumulative risk was negatively associated with maternal sensitivity across the postpartum and this effect strengthened over time. Results advance our understanding of the dynamic, transactional, and psychobiological influences on parental caregiving behaviors across the first 2 postpartum years. (PsycINFO Database Record

Maternal intimate partner violence exposure, child cortisol reactivity and child asthma.

Psychosocial stressors like intimate partner violence (IPV) exposure are associated with increased risk of childhood asthma. Longitudinal studies have not investigated the role of hypothalamic-pituitary-adrenal (HPA) axis reactivity (and associated alterations in cortisol release) in the child IPV exposure-asthma association. We sought to investigate this association, and to assess whether this relationship differs by child HPA reactivity. This secondary analysis used longitudinal cohort data from the Family Life Project. Participants included 1,292 low-income children and mothers; maternal interview and child biomarker data, including maternal report of IPV and child asthma, and child salivary cortisol obtained with validated stress reactivity paradigms, were collected when the child was 7, 15, 24, 35, and 48 months. Using structural equation modeling, maternal IPV when the child was 7 months of age predicted subsequent reports of childhood asthma (B=0.18, p=.002). This association differed according to the childs HPA reactivity status, with IPV exposed children who were HPA reactors at 7 and 15 months of age--defined as a ≥10% increase in cortisol level twenty minutes post peak arousal during the challenge tasks and a raw increase of at least .02μg/dl--being significantly at risk for asthma (7 months: B=0.17, p=.02; 15 months: B=0.17, p=.02). Our findings provide support that children who are physiologically reactive are the most vulnerable to adverse health outcomes when faced with environmental stressors.