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 (Mage = 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.

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.

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.

Salivary cortisol reactivity in preschoolers is associated with hair cortisol and behavioral problems.

The interplay between children's cortisol reactivity to challenge and cumulative cortisol exposure is not well understood. Examining the role of cortisol reactivity in early childhood may elucidate biological mechanisms that contribute to children's chronic physiological stress and behavioral dysregulation. In a sample of 65 preschool-aged children, we examined the relation between children's salivary cortisol reactivity to challenging tasks and their hair cortisol concentration (HCC). While both are biomarkers of the hypothalamic-pituitary-adrenal (HPA) axis, salivary cortisol reactivity reflects an acute cortisol response to a stressor and HCC reflects cumulative cortisol exposure. In addition, we examined the relations of these stress biomarkers with internalizing and externalizing problems. Salivary cortisol reactivity was associated with higher HCC and with increased externalizing behaviors. Child HCC also was positively correlated with parent HCC. Results highlight the contributions of salivary cortisol reactivity to children's cumulative cortisol exposure, which may add to their biological risk for health problems later. The observed association between externalizing problems and salivary cortisol reactivity indicates concordances between dysregulated behavioral reactions and dysregulated cortisol responses to challenges. The finding that salivary cortisol reactivity to challenge in early childhood plays a role in children's cumulative cortisol exposure and behavioral development suggests pathways through which cortisol reactivity may influence long-term physical and mental health.

Maternal cortisol slope at 6 months predicts infant cortisol slope and EEG power at 12 months.

Physiological stress systems and the brain rapidly develop through infancy. While the roles of caregiving and environmental factors have been studied, implications of maternal physiological stress are unclear. We assessed maternal and infant diurnal cortisol when infants were 6 and 12 months. We measured 12-month infant electroencephalography (EEG) 6-9 Hz power during a social interaction. Steeper 6-month maternal slope predicted steeper 12-month infant slope controlling for 6-month infant slope and breastfeeding. Steeper 6-month maternal slope predicted lower 6-9 Hz power. Six-month maternal area under the cuve (AUCg) was unrelated to 12-month infant AUCg and 6-9 Hz power. Psychosocial, caregiving, and breastfeeding variables did not explain results. At 6 months, maternal and infant slopes correlated, as did maternal and infant AUCg. Twelve-month maternal and infant cortisol were unrelated. Results indicate maternal slope is an informative predictor of infant physiology and suggest the importance of maternal physiological stress in this developmental period.

Variation in infant EEG power across social and nonsocial contexts.

To understand the infant social brain, it is critical to observe functional neural activation during social interaction. Yet many infant electroencephalography (EEG) studies on socioemotional development have recorded neural activity only during a baseline state. This study investigated how infant EEG power (4-6Hz and 6-9Hz) varies across social and nonsocial contexts. EEG was recorded in 12-month-olds across controlled conditions to disentangle the neural bases of social interactions. Four conditions-nonsocial, joint attention, language-only, and social engagement-were designed to tease apart how different environmental inputs relate to infant EEG power. We analyzed EEG power in frontal, central, temporal, and parietal regions. During the joint attention condition compared with the other conditions, 4-6Hz frontal, central, and parietal power was lowest, indexing greater neural activation. There was lower 4-6Hz and 6-9Hz power in the temporal region in both the joint attention and social engagement conditions compared with the nonsocial condition. In 6-9Hz, the pattern was consistent with 4-6Hz findings for the frontal region such that 6-9Hz frontal power was lower, indexing greater neural activation, in the joint attention condition compared with the nonsocial condition. There were no differences between conditions in central and parietal regions in 6-9Hz. Findings highlight the methodological importance of recording functional brain activity in multiple controlled contexts to explicate the neural bases of the infant social brain.

Exploring relationship between self-regulation dimensions and cardiac autonomic functioning in preschoolers.

The present study examined the association between behavioural dimensions of self-regulation and respiratory sinus arrhythmia (RSA), a marker of cardiac autonomic functioning in a sample of preschool children in the United States. Sixty-six children's emotion- and cognitive-oriented dimensions of self-regulation were examined with respect to changes in RSA (reactivity and recovery). Results showed that children's recovery RSA, which indicates the ability to return to homeostasis, but not reactivity, was significantly associated with the cognitive-oriented self-regulation.

Parental and Family-Level Sociocontextual Correlates of Emergent Emotion Regulation: Implications for Early Social Competence.

OBJECTIVES: Emotion regulation skills in early childhood are essential for healthy emotional and behavioral development, yet factors related to emergent emotion regulation during the early preschool period have not been extensively explored. METHODS: In the present study (N = 90), we specifically examine parental and family-level sociocontextual correlates in relation to emotion regulation skills in three-year-olds, a crucial time when the onset of several cognitive and socioemotional abilities are intertwined. We also investigate the role of these developing emotion regulatory capacities with behavioral problems and social competence. RESULTS: Children whose parents use more adaptive emotion regulation strategies (r = .33, p = .001) and who grow up in a higher income (r = .25, p = .02), less chaotic household (r = -.30, p = .004) have better emergent emotion regulation. Additionally, better child emotion regulation skills are associated with more positive outcomes such as fewer behavioral problems (r = -.46, p < .001) and more instrumental helping behaviors (r = .23, p = .04). CONCLUSIONS: Findings indicate that identifying individual differences in emotion regulation earlier than most prior studies may be particularly important for fostering this crucial skill and overall psychological well-being in young children.

A Within-subjects Experimental Protocol to Assess the Effects of Social Input on Infant EEG.

Despite the importance of social interactions for infant brain development, little research has assessed functional neural activation while infants socially interact. Electroencephalography (EEG) power is an advantageous technique to assess infant functional neural activation. However, many studies record infant EEG only during one baseline condition. This protocol describes a paradigm that is designed to comprehensively assess infant EEG activity in both social and nonsocial contexts as well as tease apart how different types of social inputs differentially relate to infant EEG. The within-subjects paradigm includes four controlled conditions. In the nonsocial condition, infants view objects on computer screens. The joint attention condition involves an experimenter directing the infant's attention to pictures. The joint attention condition includes three types of social input: language, face-to-face interaction, and the presence of joint attention. Differences in infant EEG between the nonsocial and joint attention conditions could be due to any of these three types of input. Therefore, two additional conditions (one with language input while the experimenter is hidden behind a screen and one with face-to-face interaction) were included to assess the driving contextual factors in patterns of infant neural activation. Representative results demonstrate that infant EEG power varied by condition, both overall and differentially by brain region, supporting the functional nature of infant EEG power. This technique is advantageous in that it includes conditions that are clearly social or nonsocial and allows for examination of how specific types of social input relate to EEG power. This paradigm can be used to assess how individual differences in age, affect, socioeconomic status, and parent-infant interaction quality relate to the development of the social brain. Based on the demonstrated functional nature of infant EEG power, future studies should consider the role of EEG recording context and design conditions that are clearly social or nonsocial.