Breastfeeding experience differentially impacts recognition of happiness and anger in mothers

Impact of Dysphoric Milk Ejection Reflex on Mental Health

Objective: Postpartum mental health, significantly influences breastfeeding. Dysphoric milk ejection reflex (D-MER) is defined as negative emotional reaction to milk ejection, such as unpleasant feelings, anger-irritability or a strange feeling in the stomach. This study investigates the impacts of D-MER on mothers experiencing negative emotions during breastfeeding. Method: This cross-sectional, descriptive study was conducted between July 1 and September 30, 2023 among surveyed mothers with babies of ages 0-2 experiencing discomfort while breastfeeding. Mothers reached out through Instagram and Facebook and completed a semi-structured 45-question survey using a Google form. Results: Out of 141 mothers, 27.7% (n: 39) had D-MER findings. Common emotions included tension (48%), exhaustion (43%), intolerance (41%), hypersensitivity (35%), and restlessness (33%). Symptoms reported to begin within the first month of breastfeeding in 59% of D-MER cases. Nausea was reported in 30% of mothers. The most common conditions that increased the severity of D-MER symptoms were insomnia, stress and breast fullness. Sleeping or resting, being alone, doing something else, drinking cold water, listening to music and talking to mothers who had similar experiences helped the mothers relax. In cases with D-MER findings, about 17.9% considered stopping breastfeeding, with 7.7% stopping. The postpartum depression score was ≥13 in 59% of D-MER cases. Conclusion: D-MER, which can cause early cessation of breastfeeding, may also be associated with the mother's mental health problems. Raising awareness about D-MER and equipping health professionals on this subject are important in the continuity of breastfeeding.

The evolved nest, oxytocin functioning, and prosocial development

Prosociality, orientation to attuned, empathic relationships, is built from the ground up, through supportive care in early life that fosters healthy neurobiological structures that shape behavior. Numerous social and environmental factors within early life have been identified as critical variables influencing child physiological and psychological outcomes indicating a growing need to synthesize which factors are the most influential. To address this gap, we examined the influence of early life experiences according to the evolved developmental niche or evolved nest and its influence on child neurobiological and sociomoral outcomes, specifically, the oxytocinergic system and prosociality, respectively. To-date, this is the first review to utilize the evolved nest framework as an investigatory lens to probe connections between early life experience and child neurobiological and sociomoral outcomes. The evolved nest is comprised of characteristics over 30 million years old and is organized to meet a child's basic needs as they mature. Converging evidence indicates that humanity's evolved nest meets the needs of a rapidly developing brain, optimizing normal development. The evolved nest for young children includes soothing perinatal experiences, breastfeeding, positive touch, responsive care, multiple allomothers, self-directed play, social embeddedness, and nature immersion. We examined what is known about the effects of each evolved nest component on oxytocinergic functioning, a critical neurobiological building block for pro-sociomorality. We also examined the effects of the evolved nest on prosociality generally. We reviewed empirical studies from human and animal research, meta-analyses and theoretical articles. The review suggests that evolved nest components influence oxytocinergic functioning in parents and children and help form the foundations for prosociality. Future research and policy should consider the importance of the first years of life in programming the neuroendocrine system that undergirds wellbeing and prosociality. Complex, interaction effects among evolved nest components as well as among physiological and sociomoral processes need to be studied. The most sensible framework for examining what builds and enhances prosociality may be the millions-year-old evolved nest.

Infant and maternal responses to emotional facial expressions: A longitudinal study

The current longitudinal study (N = 107) examined mothers' facial emotion recognition using reaction time and their infants' affect-based attention at 5, 7, and 14 months of age using eyetracking. Our results, examining maternal and infant responses to angry, fearful and happy facial expressions, show that only maternal responses to angry facial expressions were robustly and positively linked across time points, indexing a consistent trait-like response to social threat among mothers. However, neither maternal responses to happy or fearful facial expressions nor infant responses to all three facial emotions show such consistency, pointing to the changeable nature of facial emotion processing, especially among infants. In general, infants' attention toward negative emotions (i.e., angry and fear) at earlier timepoints was linked to their affect-biased attention for these emotions at 14 months but showed greater dynamic change across time. Moreover, our results provide limited evidence for developmental continuity in processing negative emotions and for the bidirectional interplay of infant affect-biased attention and maternal facial emotion recognition. This pattern of findings suggests that infants' affect-biased attention to facial expressions of emotion are characterized by dynamic changes.

Association between exclusive breastfeeding and postpartum post-traumatic stress disorder

BACKGROUND

Research on the association between breastfeeding and postpartum post-traumatic stress disorder (PTSD) is sparse. This study aimed to examine the association between exclusive breastfeeding up to 42 days after childbirth and postpartum PTSD.

METHODS

An epidemiologic study was conducted in a tertiary hospital in China between October 2019 and October 2020. Eligible mothers were recruited at 3 days after childbirth and assessed using the Post-Traumatic Stress Disorder Checklist - Civilian version (PCL-C) for PTSD at 42 days postpartum. The independent association between exclusive breastfeeding up to 42 days after childbirth and postpartum PTSD was estimated using log-binomial regression models, after adjusting for potential confounders.

RESULTS

Ninety-two of 759 (12.1%) mothers developed postpartum PTSD within 42 days after childbirth. Compared with partially breastfeeding mothers, exclusively breastfeeding mothers had lower risks of postpartum PTSD (relative risk [RR] 0.28; 95% confidence interval [CI] 0.13, 0.59), re-experience (RR 0.48; 95% CI 0.30, 0.76), avoidance (RR 0.55; 95% CI 0.32, 0.97), and hyperarousal (RR 0.52; 95% CI 0.34, 0.78). After adjustment for family support, parity, mode of delivery, perceived birth trauma, early contact / suckling, and rooming-in, associations between exclusive breastfeeding and postpartum PTSD remained significant: the overall PTSD adjusted relative risk [aRR] was 0.31; (95% CI 0.15, 0.66), with a re-experience aRR of 0.48; (95% CI 0.30, 0.77) and hyperarousal aRR of 0.56; (95% CI 0.37, 0.85).

CONCLUSION

Exclusive breastfeeding up to 42 days after childbirth was associated with reduced risk of postpartum PTSD. While the potential for reverse causation cannot be ruled out, strategies to improve rates of exclusive breastfeeding through teaching, counselling, and support may benefit mothers and their infants by reducing the risk of postpartum PTSD.

Impact of OXTR Polymorphisms on Subjective Well-Being: The Intermediary Role of Attributional Style

Polymorphisms in the oxytocin receptor (OXTR) gene are related to individual differences in negative emotions, such as depressive symptoms and anxiety. However, it remains unclear what the potential roles of OXTR polymorphisms are in subjective well-being (SWB), which is negatively correlated with depressive symptoms. We examined attributional styles as mediator between SWB and five polymorphisms of the oxytocin receptor gene (OXTR rs53576, rs2254298, rs1042778, rs2268494, and rs2268490) among 627 full-time college freshmen (M_age = 20.90, SD = 0.82 for male; M_age = 20.81, SD = 0.92 for female) using structural equation modeling. The results showed that individuals with the OXTR rs2254298 AA genotype and rs53576 AA/GA genotype reported higher scores on SWB, which suggested that individuals with this genotype experienced more happiness. Moreover, external attributional style partially mediated the association between OXTR rs2254298 polymorphism and SWB (β = 0.019, 95%CI [0.001, 0.036], p = 0.035). In conclusion, our findings demonstrated that the genetic variations of OXTR played a role in the individual differences of SWB, and external attribution style could mediate the association.

Dysphoric Milk Ejection Reflex: The Psychoneurobiology of the Breastfeeding Experience

Breastfeeding, given its biochemical and physiological basis, is known for its many benefits for both the lactating mother and the infant. Among the many challenges new breastfeeding mothers experience is the feeling of aversion in response to their newborn's suckling which has been termed dysphoric milk-ejection reflex (D-MER). Characterized by intense feelings of dysphoria which may eventually interfere with the mother's ability to breastfeed regularly, evidence suggests both the neurobiological and psychological basis of D-MER in an attempt to explain its complexity. Biologically, breastfeeding is expressed by the intracerebral release of oxytocin, an increased expression of oxytocin receptors in specific brain regions, increased mesocorticolimbic reward region activation, the secretion of prolactin and possibly the inhibition of dopamine. Hence, different theories explain D-MER in terms of disrupted neurotransmitter and hormonal activity. Breastfeeding has also proven to influence mood and stress reactivity in nursing mothers with a potential link with postpartum depression. Psychological theories attempt to explain D-MER from a sociopsychosexual lense shedding light on the significance of mother-infant attachment, the sexualization of the female body and the motherhood experience as a developmental stage in a woman's lifespan. The aim of this review is to provide a literature update of D-MER incorporating both neurobiological and psychological theories calling for raising awareness about the complexity of breastfeeding and for the need for mother-centered interventions for the management of D-MER and other postpartum-specific conditions.

Exploring the Prescribing Process of Domperidone for Low Milk Supply: A Qualitative Study Among Mothers, IBCLCs, and Family Doctors

BACKGROUND

When mothers are confronted with milk supply problems, taking domperidone is regularly suggested. However, domperidone has been associated with sudden cardiac death and caution in prescribing is advised. In 2016, a multidisciplinary group of authors from a tertiary academic hospital (Erasmus MC) published a clinical protocol in a leading Dutch physicians' journal to support Dutch family physicians in prescribing domperidone to stimulate lactation.

RESEARCH AIM

To explore consumer and health care provider perspectives and experiences regarding the prescribing of domperidone for lactation insufficiency following publication of a national clinical protocol.

METHODS

A cross-sectional qualitative study was performed using semi-structured interviews (N = 40) based on a topic list covering the prescribing process. Participants were mothers (n = 18) who had been advised to try domperidone to boost their milk supply between November 2016 and May 2018, their International Board Certified Lactation Consultants (n = 9), and their family physicians (n = 15). Another group of participants (mothers; n = 6) answered short questionnaires. All interviews were recorded, transcribed and analyzed using ATLAS.ti software. The resulting list of codes was organized according to the topics.

RESULTS

In the process leading to domperidone use to stimulate lactation, participant family physicians relied on the IBCLC, pharmacist, or mother to guide the prescription of domperidone, often citing the published national clinical protocol as back up. The medical safeguards incorporated in the protocol (e.g., taking medical history, physical exam, performing electrocardiograms, limiting dosage) were usually not implemented.

CONCLUSIONS

Though the availability of a national clinical protocol in which the prescribing of domperidone for lactation is supported appeared to increase the willingness of participant family physicians to prescribe, gaps were identified between clinical practice and this clinical protocol for prescribing domperidone.

Genetic variation in the oxytocin system and its link to social motivation in human infants

Frontal brain asymmetry has been linked to motivational processes in infants and adults, with left lateralization reflecting motivation to approach and right lateralization reflecting motivation to withdraw. We examined the hypothesis that variability in infants' social motivation may be linked to genetic variation in the oxytocin system. Eleven-month-old infants' brain responses and looking preferences to smiling and frowning individuals were assessed in conjunction with a polymorphism in CD38 (rs3796863) linked to autism spectrum disorder (ASD) and reduced oxytocin. Frontal brain asymmetry and looking preferences differed as a function of CD38 genotype. While non-risk A-allele carriers displayed left lateralization to smiling faces (approach) and a heightened looking preference for the individual who smiled, infants with the CC (ASD risk) genotype displayed withdrawal from smiling faces and a preference for the individual who frowned. Findings demonstrate that the oxytocin system is linked to brain and behavioral markers of social motivation in infancy.

Breastfeeding dynamically changes endogenous oxytocin levels and emotion recognition in mothers

Breastfeeding behaviours can significantly change mothers' physiological and psychological states. The hormone oxytocin may mediate breastfeeding and mothers' emotion recognition. This study examined the effects of endogenous oxytocin fluctuation via breastfeeding on emotion recognition in 51 primiparous mothers. Saliva oxytocin was assessed before and after the manipulation (breastfeeding or holding an infant), and emotion recognition tasks were conducted. Among mothers who breastfed daily, mothers with more increased levels of oxytocin after breastfeeding showed more reduced negative recognition and enhanced positive recognition of adult facial expressions. These oxytocin functions accompanying breastfeeding may support continued nurturing behaviours and also affect the general social cognition of other adults beyond any specific effect on infants.

Epigenetic dynamics in infancy and the impact of maternal engagement

The contribution of nature versus nurture to the development of human behavior has been debated for centuries. Here, we offer a piece to this complex puzzle by identifying the human endogenous oxytocin system-known for its critical role in mammalian sociality-as a system sensitive to its early environment and subject to epigenetic change. Recent animal work suggests that early parental care is associated with changes in DNA methylation of conserved regulatory sites within the oxytocin receptor gene (OXTRm). Through dyadic modeling of behavior and OXTRm status across the first year and a half of life, we translated these findings to 101 human mother-infant dyads. We show that OXTRm is dynamic in infancy and its change is predicted by maternal engagement and reflective of behavioral temperament. We provide evidence for an early window of environmental epigenetic regulation of the oxytocin system, facilitating the emergence of individual differences in human behavior.

Psychological effects of breastfeeding on children and mothers

While the nutritional and physical health benefits of breastfeeding are well established, accumulating research demonstrates the far-reaching psychological effects of breastfeeding on children and their mothers. Here, we provide a non-exhaustive review of the empirical evidence, showing that breastfeeding impacts children's brain, cognitive, and socio-emotional development. In mothers, research is presented indicating that breastfeeding influences mood, affect, stress, and maternal care. The current review aims to provide a broad overview of existing findings on the psychological effects of breastfeeding, highlighting the important role that breastfeeding plays across several dimensions of psychological functioning. We also discuss the potential mechanisms that may underpin the observed effects, provide a constructive commentary on the limitations of the existing work, and put forth some considerations when evaluating this line of research.

Epigenetic modification of the oxytocin receptor gene is associated with emotion processing in the infant brain

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First developmental neuroimaging epigenetics study with human infants.

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Oxytocin receptor gene methylation (OXTRm) assessed in a large sample of infants.

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OXTRm predicts inferior frontal brain responses to emotional faces using fNIRS.

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Higher OXTRm linked to enhanced brain responses to angry and fearful faces.

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OXTRm contributes to variability in social brain function early in ontogeny.

The neural capacity to discriminate between emotions emerges early in development, though little is known about specific factors that contribute to variability in this vital skill during infancy. In adults, DNA methylation of the oxytocin receptor gene (OXTRm) is an epigenetic modification that is variable, predictive of gene expression, and has been linked to autism spectrum disorder and the neural response to social cues. It is unknown whether OXTRm is variable in infants, and whether it is predictive of early social function. Implementing a developmental neuroimaging epigenetics approach in a large sample of infants (N = 98), we examined whether OXTRm is associated with neural responses to emotional expressions. OXTRm was assessed at 5 months of age. At 7 months of age, infants viewed happy, angry, and fearful faces while functional near-infrared spectroscopy was recorded. We observed that OXTRm shows considerable variability among infants. Critically, infants with higher OXTRm show enhanced responses to anger and fear and attenuated responses to happiness in right inferior frontal cortex, a region implicated in emotion processing through action-perception coupling. Findings support models emphasizing oxytocin’s role in modulating neural response to emotion and identify OXTRm as an epigenetic mark contributing to early brain function.

Perceived Intensity of Emotional Point-Light Displays is Reduced in Subjects with ASD

One major characteristic of autism spectrum disorder (ASD) is problems with social interaction and communication. The present study explored ASD-related alterations in perceiving emotions expressed via body movements. 16 participants with ASD and 16 healthy controls observed video scenes of human interactions conveyed by point-light displays. They rated the valence of the depicted emotions in terms of their intensity and judged their confidence in their ratings. Results showed that healthy participants rated emotional interactions displaying positive emotionality as being more intense and were more confident about their ratings than ASD subjects. Results support the idea that patients with ASD have an altered perception of emotions. This extends research on subjective features (intensity, confidence) of emotion perception to the domain of emotional body movements and kinematics.

Maternal nurturing experience affects the perception and recognition of adult and infant facial expressions

The perception and recognition of facial expressions are crucial for parenting. This study investigated whether and how maternal nurturing experience and trait anxiety influence the perception and recognition of infant and adult facial expressions. This was assessed by comparing the performance of primiparous mothers (n = 25) and non-mothers (n = 28) on an emotional face perception task. Trait anxiety was measured using the Japanese version of the State-Trait Anxiety Inventory (STAI). We found that mothers had higher recognition accuracy for facial expressions, but only of adults, not infants. Moreover, as trait anxiety increased, so did mothers’ sensitivity in perceiving facial expressions of both infants and adults. These findings suggest that maternal nurturing experience does enhance the recognition of adult emotional expressions, and an optimal level of maternal trait anxiety may enhance mothers’ sensitivity toward infants’ and adults’ emotional signals.

Breastfeeding and Adult Personality

Five Factor Model (FFM) personality traits are implicated in long-term health-risk behaviors and outcomes. Less research has addressed how early-life experiences are associated with individual differences in these traits in adulthood. We examine whether having been breastfed is associated with adult personality and well-being in the National Longitudinal Study of Adolescent to Adult Health. At Wave 1, caregivers reported whether the target child had been breastfed. At Wave 4, participants (N=13,113; 53% female; M_age=28.98) completed measures of psychological functioning. We tested for mean-level differences in the traits by breastfeeding status (yes/no) and by the duration of breastfeeding, controlling for basic demographic factors and early-life factors that could confound the breastfeeding-personality association (e.g., mother education). Participants who had been breastfed scored lower in neuroticism, anxiety, and hostility and higher in openness and optimism than those not breastfed. A curvilinear relation suggested that neuroticism was lowest for those breastfed for 9-12 months and highest for those either breastfed for >24 months or exclusively bottle-fed. Breastfeeding was unrelated to conscientiousness or state psychological functioning. This research suggests long-term psychological benefits to breastfeeding and indicates that early life experiences are associated with traits that are consequential for adult health.

Genetic variation in CD38 and breastfeeding experience interact to impact infants' attention to social eye cues

Attending to emotional information conveyed by the eyes is an important social skill in humans. The current study examined this skill in early development by measuring attention to eyes while viewing emotional faces in 7-mo-old infants. In particular, we investigated individual differences in infant attention to eyes in the context of genetic variation (CD38 rs3796863 polymorphism) and experiential variation (exclusive breastfeeding duration) related to the oxytocin system. Our results revealed that, whereas infants at this age show a robust fear bias (increased attention to fearful eyes), their attention to angry and happy eyes varies as a function of exclusive breastfeeding experience and genetic variation in CD38. Specifically, extended exclusive breastfeeding duration selectively enhanced looking preference to happy eyes and decreased looking to angry eyes. Importantly, however, this interaction was impacted by CD38 variation, such that only the looking preferences of infants homozygous for the C allele of rs3796863 were affected by breastfeeding experience. This genotype has been associated with reduced release of oxytocin and higher rates of autism. In contrast, infants with the CA/AA genotype showed similar looking preferences regardless of breastfeeding exposure. Thus, differences in the sensitivity to emotional eyes may be linked to an interaction between the endogenous (CD38) and exogenous (breastfeeding) availability of oxytocin. These findings underline the importance of maternal care and the oxytocin system in contributing to the early development of responding to social eye cues.

Duration of exclusive breastfeeding is associated with differences in infants' brain responses to emotional body expressions

Much research has recognized the general importance of maternal behavior in the early development and programing of the mammalian offspring's brain. Exclusive breastfeeding (EBF) duration, the amount of time in which breastfed meals are the only source of sustenance, plays a prominent role in promoting healthy brain and cognitive development in human children. However, surprisingly little is known about the influence of breastfeeding on social and emotional development in infancy. In the current study, we examined whether and how the duration of EBF impacts the neural processing of emotional signals by measuring electro-cortical responses to body expressions in 8-month-old infants. Our analyses revealed that infants with high EBF experience show a significantly greater neural sensitivity to happy body expressions than those with low EBF experience. Moreover, regression analyses revealed that the neural bias toward happiness or fearfulness differs as a function of the duration of EBF. Specifically, longer breastfeeding duration is associated with a happy bias, whereas shorter breastfeeding duration is associated with a fear bias. These findings suggest that breastfeeding experience can shape the way in which infants respond to emotional signals.