Salivary α-amylase and intended harsh caregiving in response to infant crying: evidence for physiological hyperreactivity

Family instability, parenting, and child externalizing problems: Moderation by maternal sympathetic stress reactivity

This multi-method longitudinal study evaluated how changes in maternal sensitive parenting may operate as an indirect factor linking family instability and the development of child externalizing problems over time. This study also investigated how mothers' stress reactivity within the sympathetic nervous system (SNS) may moderate the association between family instability and the development of maternal sensitivity. Participants were 235 families with a young child (Mage = 2.97 years at the first measurement occasion) and these families were followed for two annual measurement occasions. Maternal sensitivity was observed during two discipline tasks (i.e., forbidden toy, discipline discussion tasks), and maternal SNS stress reactivity was indicated by their salivary alpha-amylase (sAA) reactivity to an interpersonal stressor. Findings revealed significant direct effects of family instability and family instability-x-sAA reactivity interaction in association with the change in maternal sensitivity over time. For both tasks, mothers with greater sAA reactivity exhibited stronger associations between family instability and the growth of their sensitivity. Tests of indirect effects indicated that change in maternal sensitivity operated as an indirect factor between family instability-x-sAA reactivity interaction and the change in child externalizing problems. The present findings have important implications for understanding parental and child sequelae associated with unstable family contexts.

The dark side of fear expression: Infant crying as a trigger for maladaptive parental responses

While infant fearfulness, and its expression via crying, may have been adaptive in our evolutionary history, for modern parents, crying can be challenging to respond to. We discuss how and why prolonged crying can raise the risk for difficulties with adult care. Given that crying is the most-reported trigger for shaking, its potential to elicit maladaptive responses should not be overlooked.

The causal effect of household chaos on stress and caregiving: An experimental study

The correlational nature of previous studies on household chaos does not allow claims about causal effects of household chaos. The present study used an experimental design to assess the causal effect of household chaos on stress, negative emotions, and caregiving. Ninety-six female students (18–25 years) participated in our study. They took care of an infant simulator in a normal living room (neutral condition), and a chaotic living room (chaos condition), while caregiver sensitivity was observed, operationalized as perceiving, correctly interpreting, and responding accurately and promptly to the infant's signals. Participants reported on their current emotional state, and saliva was collected four times for analysis of salivary alpha-amylase (sAA). Results showed that there were no significant time or condition effects on negative emotional state. Yet, sAA levels were higher in the chaos condition compared to the neutral condition. We found no evidence for negative emotional state or sAA mediating the relation between household chaos and caregiver sensitivity. Because household chaos affected physiological stress in a parenting situation, it should not be ignored when using interventions aimed at reducing stress in parents. More research is needed on the effect of reduced (as opposed to increased) levels of household chaos on physiological stress levels in families with young children.

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Household chaos is causally related to physiological stress in a caregiving context.

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Household chaos does not affect self-reported negative emotions.

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No evidence for stress mediating the relation between household chaos and caregiving.

Differential Effects of Infant Vocalizations on Approach-Avoidance Postural Movements in Mothers

Infant vocalization plays a pivotal role in communicating infant mood to parents and thereby motivating parenting responses. Although many psychological and neural responses to infant vocalization have been reported, few studies have examined maternal approach-avoidance behavior in response to infant vocalization. Thus, this research sought to determine how infant emotional vocalization affects maternal behavior. Twenty mothers participated in this behavioral study, all of whom had infants of 24 months old or less. In the experiment, they stood on a Balance Board that collected real-time data regarding center of pressure (COP), while listening to a series of infant vocalizations including cry, laugh, and babbling. They then listened to the same vocalizations for a second time and rated their felt emotions in response to each vocalization. The participants demonstrated significant postural movements of approaching in response to cry stimuli or to stimuli regarded as highly urgent. In contrast, they demonstrated postural movement of avoidance in response to laugh vocalization. These findings suggest that parenting behavior in response to infant emotional vocalization is regulated not by the pleasant-unpleasant axis but by the urgency of the stimulus.

Vasopressin Differentially Affects Handgrip Force of Expectant Fathers in Reaction to Own and Unknown Infant Faces

The underlying mechanisms of paternal responses to infant signals are poorly understood. Vasopressin has previously been proposed to affect these responses. Using a double-blind, placebo-controlled, within-subject design (N = 25 expectant fathers), we examined the effect of vasopressin administration on the use of excessive handgrip force during exposure to infant crying versus matched control sounds, while participants saw morphed images representing their own infant versus an unknown infant. We found that, compared to placebo, AVP administration elicited more excessive force while viewing an unknown infant image compared to viewing the image representing one’s own infant, while the reverse was true under placebo. The results are discussed in light of vasopressin’s role in parenting and parental protection among human fathers.

Prenatal and postnatal cortisol and testosterone are related to parental caregiving quality in fathers, but not in mothers

Testosterone and cortisol have both been implicated in human parenting behavior. We investigated the relations between observed quality of caregiving during parent-child interactions and pre- and postnatal testosterone and cortisol levels, in both mothers (N = 88) and fathers (N = 57). Testosterone and cortisol were measured before and after interaction with an infant simulator (prenatal) and with their own child (postnatal) to index basal levels as well as steroid reactivity to the interaction. Our findings are that in fathers, interactions between cortisol and testosterone are related to quality of caregiving both pre- and postnatally. Prenatally there was a stronger negative relation between T and quality of caregiving in fathers with lower cortisol levels, and postnatally there was a stronger negative relation between cortisol and quality of caregiving in fathers high in testosterone levels. Furthermore, prenatal cortisol levels were related to paternal quality of caregiving during interaction with their own child. In mothers, no associations between quality of caregiving and our endocrine measures were observed. We interpret our findings in the context of hyperreactive physiological responses observed in parents at risk for insensitive caregiving, and in light of the dual-hormone hypothesis. The current findings contribute to the growing literature on the endocrine antecedents of human caregiving behavior.

The past is present: The role of maltreatment history in perceptual, behavioral and autonomic responses to infant emotional signals

In the current study associations between parents' experiences of childhood maltreatment and their perceptual, behavioral and autonomic responses to infant emotional signals were examined in a sample of 160 parents. Experienced maltreatment (both physical and emotional abuse and neglect) was reported by the participants and, in approximately half of the cases, also by their parents. During a standardized infant vocalization paradigm, participants were asked to squeeze a handgrip dynamometer at maximal and at half strength while listening to infant crying and laughter sounds and to rate their perception of the sounds. In addition, their heart rate (HR), pre-ejection period (PEP), and vagal tone (RSA) were measured as indicators of underlying sympathetic and parasympathetic reactivity. Results indicated that participants did not differ in their perceptions of the infant vocalizations signals according to their maltreatment experiences. However, maltreatment experiences were associated with the modulation of behavioral responses. Experiences of neglect during childhood were related to more handgrip force during infant crying and to less handgrip force during infant laughter. Moreover, a history of neglect was associated with a higher HR and a shorter PEP during the entire infant vocalization paradigm, which may indicate chronic cardiovascular arousal. The findings imply that a history of childhood neglect negatively influences parents' capacities to regulate their emotions and behavior, which would be problematic when reacting to children's emotional expressions.

The Association of Maternal Exposure to Domestic Violence During Childhood With Prenatal Attachment, Maternal-Fetal Heart Rate, and Infant Behavioral Regulation

Human and animal models suggest that maternal hormonal and physiological adaptations during pregnancy shape maternal brain functioning and behavior crucial for offspring care and survival. Less sensitive maternal behavior, often associated with psychobiological dysregulation and the offspring's behavioral and emotional disorders, has been observed in mothers who have experienced adverse childhood experiences. Strong evidence shows that children who are exposed to domestic violence (DV) are at risk of being abused or becoming abusive in adulthood. Yet little is known about the effect of childhood exposure to DV on the expecting mother, her subsequent caregiving behavior and related effects on her infant. Thus, the present study examined the association of maternal exposure to DV during childhood on prenatal maternal attachment, maternal heart rate reactivity to an infant-crying stimulus and post-natal infant emotional regulation. Thirty-three women with and without exposure to DV during childhood were recruited during the first trimester of pregnancy and followed until 6-month after birth. The Maternal Antenatal Attachment Scale (MAAS) was used to measure prenatal attachment of the mother to her fetus during the second trimester of pregnancy, maternal and fetal heart rate reactivity to an infant-crying stimulus was assessed at the third trimester of pregnancy, and the Infant Behavior Questionnaire-Revised (IBQ-R) was used to assess infant emotional regulation at 6-months. Results showed that pregnant women that were exposed to DV during childhood had a poorer quality of prenatal attachment of mother to fetus, regardless of whether they also experienced DV during adulthood. In addition, maternal exposure to DV during childhood was associated with increased maternal heart rate to infant-crying stimulus and worse infant emotional regulation. These findings highlight the importance of prenatal screening for maternal exposure to DV during childhood as a risk factor for disturbances in the development of maternal attachment, dysfunctional maternal behavior and emotion dysregulation.

Hormonal and Neuromuscular Responses to Breastfeeding: A Pilot Study

OBJECTIVES

Difficult breastfeeding in the first weeks after birth may result in muscle tension in infants and activation of the maternal hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS). Our primary objective was to examine the feasibility of collecting neuroendocrine markers of maternal HPA axis and SNS activation (salivary cortisol and α-amylase [sAA]) and electromyographic (EMG) markers of infant distress during feeding in the first 2 weeks after birth. We also examined the relationships of these indices to each other and to mother-infant interactive behaviors during feeding.

METHODS

We recruited mothers in the postpartum unit of a teaching hospital and observed a feeding in the dyad's home. Cortisol and sAA were sampled before feeding, 10 min into feeding, at feeding end, and 20 min after feeding. Infant muscle activity was recorded continuously with an EMG data logger. We used the Nursing Child Assessment Feeding Scale to measure mother-infant interaction.

RESULTS

The 20 mothers reported no disruption to breastfeeding and no change in infant behavior due to collection measures. Mean cortisol levels decreased significantly; there was no significant change in sAA levels. Relationships were found between interactive behavior and trends in neuroendocrine biomarkers. Longer bursts of infant muscle activity were associated with higher levels of maternal cortisol during feeding but not mother-infant interactive behaviors.

CONCLUSIONS

Maternal salivary biomarkers and their association with feeding behaviors can be a useful tool for clinical longitudinal research beginning soon after birth. Infant EMG data may be useful for assessing maternal arousal.

Salivary α-Amylase Reactivity to Infant Crying in Maltreating Mothers

Deviant physiological reactivity to infant stimuli has been suggested to underlie maladaptive parenting behavior. Our study involved 44 maltreating and 42 non-maltreating mothers. During a standardized cry paradigm, mothers listened to nine cry sounds of varying pitches. Saliva was collected at baseline, after each cry sound, and after a recovery episode. Salivary α-amylase (sAA) as a marker of autonomic nervous system (ANS) activity was assayed from saliva samples. Maltreating mothers showed lower overall sAA levels and an attenuated reactivity pattern to infant crying as compared to non-maltreating mothers. No effect of type of maltreatment (neglect only vs. neglect and abuse) was found. Furthermore, positive correlations between sAA and heart rate (HR) for non-maltreating mothers differed significantly from non-significant correlations between sAA and HR for maltreating mothers. This suggests anomalous asynchrony between different aspects of the ANS in maltreating mothers. Results indicate a lack of functional autonomic (re)activity as a contributing risk factor to child maltreatment.

Handgrip force of maltreating mothers in reaction to infant signals

Handgrip force responses to infant signals were examined in a sample of 43 maltreating and 40 non-maltreating mothers. During a standardized handgrip paradigm, mothers were asked to squeeze a handgrip dynamometer at maximal and at half of their maximal handgrip strength while listening to infant crying and laughter sounds. Maltreating mothers used excessive force more often while listening to infant crying and laughter than non-maltreating mothers. Of the maltreating mothers, only neglectful mothers (n=20) tended to use excessive force more often during crying than non-maltreating mothers. Participants did not rate the sounds differently, indicating that maltreating mothers cannot be differentiated from non-maltreating mothers based on their perception of infant signals, but show different behavioral responses to the signals. Results imply that, in response to infant signals (i.e., crying or laughing), maltreating mothers may be insufficiently able to regulate the exertion of physical force.

Maternal-child adrenocortical attunement in early childhood: continuity and change

This study evaluated continuity and change in maternal-child hypothalamic-pituitary-adrenal axis attunement in early childhood. Participants were drawn from a prospective study of 1,292 mother-child dyads, which were racially diverse, predominantly low-income, and non-urban. Child focused stress tasks designed to elicit anger, fear, and frustration were administered during early infancy, later infancy, and toddlerhood. Mothers' and children's saliva samples (later assayed for cortisol) were collected before and after the tasks. The strength of mother-child adrenocortical attunement was conserved across infancy and toddlerhood. The magnitude of maternal-child adrenocortical attunement decreased in response to the child-focused stress tasks. Maternal sensitivity and the child's task-related emotional reactivity moderated adrenocortical attunement across the task, with greater maternal sensitivity during a free-play, and lower levels of child emotional reactivity during the stress tasks, stabilizing attunement from pre- to post-task levels. The findings advance our understanding of individual differences in the social regulation of adrenocortical activity in early childhood.

Autonomic Reactivity to Infant Crying in Maltreating Mothers

We examined autonomic reactivity to infant crying in a sample of 42 maltreating and 38 non-maltreating mothers. Exploratively, we tested if differential reactivity was related to child neglect versus the combination of neglect and abuse, and we tested whether mothers' experiences with maltreatment in their own childhood moderated the association between their current maltreatment status and physiology. During a standardized cry paradigm, mothers listened to cry sounds of various pitches. Heart rate (HR), pre-ejection period (PEP), skin conductance levels (SCLs), and vagal tone (root mean square of successive differences [RMSSD]) were measured as indicators of underlying sympathetic and parasympathetic reactivity. The maltreating mothers showed lower SCL reactivity to the cry sounds than non-maltreating mothers. Furthermore, significant negative correlations between HR and PEP in the non-maltreating group differed from nonsignificant correlations in the maltreating group, which suggests a lack of sympathetic cardiac control in maltreating mothers. We found no differences between neglectful mothers and those who were additionally abusive. Together, our findings support the notion of sympathetic hypoarousal as a risk factor for child maltreatment, which may be indicative of disengagement in a caregiving context. Intervention programs might focus on improving maternal sensitivity to improve responsiveness to child signals.

Maternal overreactive sympathetic nervous system responses to repeated infant crying predicts risk for impulsive harsh discipline of infants

Physiological reactivity to repeated infant crying was examined as a predictor of risk for harsh discipline use with 12-month-olds in a longitudinal study with 48 low-income mother-infant dyads. Physiological reactivity was measured while mothers listened to three blocks of infant cry sounds in a standard cry paradigm when their infants were 3 months old. Signs of harsh discipline use were observed during two tasks during a home visit when the infants were 12 months old. Mothers showing signs of harsh discipline (n = 10) with their 12-month-olds were compared to mothers who did not (n = 38) on their sympathetic (skin conductance levels [SCL]) and parasympathetic (respiratory sinus arrhythmia) reactivity to the cry sounds. Results showed a significant interaction effect for sympathetic reactivity only. Mean SCL of harsh-risk mothers showed a significant different response pattern from baseline to crying and onward into the recovery, suggesting that mean SCL of mothers who showed signs of harsh discipline continued to rise across the repeated bouts of cry sounds while, after an initial increase, mean SCL level of the other mothers showed a steady decline. We suggest that harsh parenting is reflected in physiological overreactivity to negative infant signals and discuss our findings from a polyvagal perspective.