A Caretaker Acute Stress Paradigm: Effects on behavior and physiology of caretaker and infant

Preliminary findings on the association between maternal salivary and hair cortisol and the mother-infant-interaction during the early postpartum period

Maternal capabilities to engage in sensitive caregiving are important for infant development and mother-infant-interaction, however, can be negatively affected by cortisol due to a stress response. Previous research suggested that cortisol possibly impairs cognitive functions important for caregiving behavior, which potentially leads to less maternal sensitivity. However, studies investigating the influence of cortisol using endocrine parameters on the mother-infant-interaction during the early postpartum are lacking. In the current study, fifty-nine mother-infant-dyads participated in a laboratory face-to-face still-face (FFSF) observation when infants were 4 months of age. Maternal and infant positive, negative and matched behavior during the FFSF was microanalytically coded. Cortisol concentrations were obtained using hair and saliva samples. For salivary cortisol, the area under the curve with respect to ground (AUCG) was calculated using two saliva samples obtained after arrival and after the FFSF. Multiple block-wise hierarchical linear regression models were conducted to incorporate potential confounding factors (maternal age, parity, infant gestational age, infant sex) in a first step and, then, test for the association of hair and salivary cortisol with maternal and infant positive, negative and dyadic behavior in a second step. For both it was hypothesized that cortisol assessed in hair and saliva is negatively associated with positive and matched mother-infant-interaction, and positively associated with negative mother-infant-interaction. It could be shown that salivary but not hair cortisol as well as infant gestational age and infant sex related significantly to infant positive and negative affect as well as matched behavior during the reunion phase of the FFSF. Maternal positive affect was unrelated to any of the variables. The results are discussed in regard to the importance of maternal cortisol levels over a longer period of time and more acute situational levels for the mother-infant-interaction as well as the relevance of included confounding factors.

Mother-infant stress contagion? Effects of an acute maternal stressor on maternal caregiving behavior and infant cortisol and crying

BACKGROUND

Postpartum maternal distress has been associated with adverse infant outcomes. A potential pathway of how maternal distress affects infant outcomes could be alterations in maternal caregiving behavior. However, the associations between maternal distress, caregiving behavior, and infant outcomes have never been tested in a controlled experiment. This preregistered study utilized an experimental design to investigate the effects of an acute maternal stressor on infant cortisol and crying and the possible mediating role of maternal caregiving behavior.

METHODS

Mother-infant dyads (N = 91) participated in a lab visit at 8 weeks postpartum, where mothers were separated from their infants to either perform a Trier Social Stress Test (TSST) or a control task. The task was immediately followed by a mother-infant interaction to assess maternal caregiving behavior and infant cortisol and crying.

RESULTS

Our structural equation model found no differences between conditions (stressor/control) on maternal caregiving behavior and infant response to maternal stress. Secondary findings revealed that higher quality of maternal caregiving behavior was related to lower levels of infant crying and lower cortisol levels at the end of the visit, but not cortisol at reunion.

CONCLUSIONS

Our findings do not support the occurrence of mother-infant stress contagion in this experimental setting but do indicate a link between maternal caregiving behavior and infant behavioral and cortisol responses. Given the high prevalence of maternal mental health problems and their possible negative association with offspring development, further (experimental) research is needed to understand just how maternal postpartum distress affects young infants.

Infants show negative changes in affect and physiology when re-experiencing a stressor, its context, and a positive event 24-h later

Exposure to early life stress shapes further development, affects later stress reactivity, and mental health outcomes. Despite the central role of early experiences, there is little understanding of how these rapidly forgotten events gain their influence. An infant's ability to cope with everyday stressors is founded on successful co-regulation through mother-infant interaction. A significant disruption of this interaction through the Face-to-Face Still-Face paradigm elicits a well-documented behavioral and physiological stress response in infants. What has yet to be explored is whether infants show regulatory adaptions when encountering the situation over again. To fill this gap, 80 mother-infant dyads were observed in the lab on two consecutive days. Infants in the experimental condition (n = 40) were exposed to a double Still-Face paradigm on day one. Infants in the control group (n = 40) completed time-matched episodes of typical play during their first visit. Mother-infant dyads from both groups returned to the lab 24 h later and participated in the double Still-Face paradigm. Changes in behavior (positive and negative affect), physiology (heart rate), and salivary cortisol, compared to day one and between groups, were evaluated and used to infer adaption to the previous experienced laboratory visit. Infants in the experimental condition showed a significant decrease in positive affect (p = 0.016) and an increase in heart rate (p < 0.001) on day two, compared to controls, even during baseline measures and a neutral first play episode. Infants in the control condition showed a significant decrease in affect (p = 0.05) and non-significant increase in heart rate on day two when first encountering the Still-Face paradigm. Infants in the experimental condition showed significant higher heart rate on day two compared to the control group (p = 0.046). Infants in the experimental condition also exhibited a marginally significant increase in salivary cortisol on day two, compared to day one (p = 0.054). The change in infant heart rate was independent of maternal heart rate which did not differ between day one and day two, or between groups. Findings suggest that a previous stressful experience may elicit a behavioral and physiological adaption in infants 24 h later. Our results suggest that even a short, acute stressful event can elicit a lasting stress response in infants 24 h later. The effect we observed was specific to the context of the stressful event, not just the stressor. More precisely, the effect "spilled over" from the stressful experience on day one into the baseline measure of day two, usually a neutral experience. The results could have implications for further research on how stressful experiences may shape the stress response.

Maternal heart rate variability at 3-months postpartum is associated with maternal mental health and infant neurophysiology

Previous research has demonstrated a critical link between maternal mental health and infant development. However, there is limited understanding of the role of autonomic regulation in postpartum maternal mental health and infant outcomes. In the current study, we tested 76 mother-infant dyads from diverse socioeconomic backgrounds when infants were 3-months of age. We recorded simultaneous ECG from dyads while baseline EEG was collected from the infant; ECG heart rate variability (HRV) and EEG theta-beta ratio and alpha asymmetry were calculated. Dyadic physiological synchrony was also analyzed to better understand the role of autonomic co-regulation. Results demonstrated that lower maternal HRV was associated with higher self-reported maternal depression and anxiety. Additionally, mothers with lower HRV had infants with lower HRV. Maternal HRV was also associated with higher infant theta-beta ratios, but not alpha asymmetry. Exploratory analyses suggested that for mother-infant dyads with greater physiological synchrony, higher maternal HRV predicted increased infant theta-beta ratio via infant HRV. These findings support a model in which maternal mental health may influence infant neurophysiology via alterations in autonomic stress regulation and dyadic physiological co-regulation.

The Neurobiology of Infant Attachment-Trauma and Disruption of Parent-Infant Interactions

Current clinical literature and supporting animal literature have shown that repeated and profound early-life adversity, especially when experienced within the caregiver-infant dyad, disrupts the trajectory of brain development to induce later-life expression of maladaptive behavior and pathology. What is less well understood is the immediate impact of repeated adversity during early life with the caregiver, especially since attachment to the caregiver occurs regardless of the quality of care the infant received including experiences of trauma. The focus of the present manuscript is to review the current literature on infant trauma within attachment, with an emphasis on animal research to define mechanisms and translate developmental child research. Across species, the effects of repeated trauma with the attachment figure, are subtle in early life, but the presence of acute stress can uncover some pathology, as was highlighted by Bowlby and Ainsworth in the 1950s. Through rodent neurobehavioral literature we discuss the important role of repeated elevations in stress hormone corticosterone (CORT) in infancy, especially if paired with the mother (not when pups are alone) as targeting the amygdala and causal in infant pathology. We also show that following induced alterations, at baseline infants appear stable, although acute stress hormone elevation uncovers pathology in brain circuits important in emotion, social behavior, and fear. We suggest that a comprehensive understanding of the role of stress hormones during infant typical development and elevated CORT disruption of this typical development will provide insight into age-specific identification of trauma effects, as well as a better understanding of early markers of later-life pathology.

Acute Maternal Stress Disrupts Infant Regulation of the Autonomic Nervous System and Behavior: A CASP Study

Exposure to maternal stress is assumed to influence infant health and development across the lifespan. The autonomic nervous system (ANS) is especially sensitive to the effects of the early caregiving environment and linked to predictors of later mental health. Understanding how exposure to maternal stress adversely affects the developing ANS could inform prevention. However, there is no agreed upon definition of maternal stress making its study difficult. Here we use the Caretaker Acute Stress Paradigm (CASP) to study the effects of maternal stress in an experimentally controlled laboratory setting. The CASP has 5 episodes, a natural play, followed by a caretaker stressor (or control) condition, another play, a classic still face episode, followed by another play. A total of 104 4-months-old infants and their mothers were randomly assigned to either the caretaker-stress or caretaker-control condition. Changes in behavior, heart rate (HR), and respiratory sinus arrhythmia (RSA) before and after the introduction of the stressor (or control condition) were recorded and compared. Infants in the maternal stress condition showed significantly more behavioral distress [X 2 = (1, N = 104) = 4.662, p = 0.031]. Moreover, infants whose mothers were in the stress condition showed an significant increase in heart rate after the caretaker condition [F (1, 102) = 9.81, p = 0.002]. Finally we observed a trend to faster RSA recovery in infants of the control condition [F (1, 75) = 3.539, p = 0.064]. Results indicate that exposure to acute maternal stress affects infant regulation of the autonomic nervous system and behavior.

Caregiver and Young Child Biological Attunement In Distress Contexts: A Systematic Review and Narrative Synthesis

The objective of the current study was to systematically review the literature on caregiver-child biological attunement within distress contexts during the first three years of life. A total of 9932 unique abstracts were identified through Medline, Embase, PsycINFO, CINAHL, and Scopus databases. Thirty-six studies provided data from caregivers and their infants or toddlers within a distress paradigm, used biological indicators of distress, and assessed the relations between caregiver and child biological indicators. Findings were synthesized based on biological indicators, type of analysis, and measurement epochs pre- and post-distress. Most articles examined cortisol. Associations between caregiver and child cortisol indicators were moderate to large, though findings varied depending on the analysis used and measurement epochs examined. Many of the findings examining relations between mother and child cardiac, sAA, and EEG indicators were weak or inconsistent, likely due to the limitations of methodological approaches used to capture the complexity of the caregiver-child attunement process. Gaps in the literature and suggestions for future research are discussed.

Reconceptualizing non-pharmacologic approaches to Neonatal Abstinence Syndrome (NAS) and Neonatal Opioid Withdrawal Syndrome (NOWS): A theoretical and evidence-based approach. Part II: The clinical application of nonpharmacologic care for NAS/NOWS

There has been increasing emphasis on the importance of the development of self-regulatory capacities of the individual as the cornerstone of development. The caregivers' abilities to manage their own attention, emotions, physiology and behaviors influence the development of the child's self-regulatory and interactive capacities, and thereby their overall development. Newborns prenatally exposed to psychoactive substances and/or to other prenatal stressors such as maternal poor nutrition, increased maternal stress, trauma, difficult and/or impoverished environments, in tandem with genetic predispositions, can result in alterations to their neurodevelopment that predispose them to self-regulatory problems that can be expressed at any stage of life. The care of infants with Neonatal Abstinence Syndrome (NAS)/Neonatal Opioid Withdrawal Syndrome (NOWS) and their mother/caregiver is a window of opportunity to assess the regulatory and co-regulatory capacities of both, and to provide holistic interventions with the goal of empowering the mother/caregiver in their own self-knowledge/self-regulation capacities and their crucial role in promoting the healthy development of their children. Non-pharmacologic care for the infant with NAS/NOWS is the first line of treatment and of paramount importance. Yet, current approaches are based on a limited scope of infant functioning, and the scoring systems in current use do not result in individualized and specific non-pharmacologic care of the infant, which can result in excessive or insufficient medication and a lack of caregiver appreciation for the infant's strengths, difficulties and early development. The interventions described here are based on the infant's signs of dysregulation in four neurobehavioral subsystems that can be dysregulated by NAS/NOWS, the infant's adaptive or maladaptive responses to return to a regulated functioning, and the co-regulatory behaviors of the infant and the mother/caregiver. In Part I of this two-part series on re-conceptualizing non-pharmacologic care for NAS/NOWS we laid the foundation for a new treatment approach, one grounded in developmental theory and evidence-based observations of infant and interpersonal neurobiology. Here, in Part II, we outline actionable, individually tailored evaluations and approaches to non-pharmacologic NAS/NOWS treatment based on strategies to support the regulatory capacities and development of 4 key domains: 1) autonomic; 2) motor/tone; 3) sleep/awake state control; and 4) sensory modulation subsystems.

Studying caregiver-infant co-regulation in dynamic, diverse cultural contexts: A call to action

Caregivers and infants co-regulate their physiology, emotions, and behavior in a way that is dynamically responsive to each other and the contexts in which they live. This paper is an introduction and call to action for researchers interested in understanding how to study caregiver-infant interactions in the home and diverse cultural contexts, including marginalized communities. We argue that research will be more valid, culturally relevant, and tapped-in to the daily lives of caregivers and infants if there is partnership and collaboration with the caregivers in the design of the questions, data collection and analysis, and distribution of the findings. We recommend dynamically assessing emotions, behaviors, and physiology using repeated sampling methods including ecological momentary assessments (EMA), salivary bioscience, and actigraphy. We aim to extend current practices of studying caregiver-infant co-regulation by measuring fluctuations of daily life and considering sociocultural factors that shape naturalistic caregiver-infant interactions. Using methodological advancements and community-based participatory research approaches can enable developmental scientists to measure life as it is actually lived.