Influence of oxytocin on parenting behaviors and parent-child bonding: A systematic review

Oxytocin enhances acquisition in a social trust task in mice, whereas both oxytocin and its antagonist block trust violation learning

The complex effects of the neurohormone oxytocin (OT) on socio-cognitive phenomena have recently been proposed to be complementary with safety learning, where a stimulus acquires safety-predicting properties when it predicts non-occurrence of an aversive event. OT may enhance salience of safety stimuli and promote positive social behavior, such as trust, by reducing anxiety and stress. Complementary, OT may reduce the ability to modulate previously learned behaviors based on new, contradicting information. This occurs through its attenuation of prediction error (PE)-the discrepancy between expectations and actual outcomes. In the current study, we modulated OT receptor (OTR) activity by administering an agonist (OT) and antagonist (cligosiban, CL), and subjected male and female mice to our social transmission of food preference (STFP) protocol to assess social safety learning. STFP is based on the observation that food neophobia of rodents is attenuated when a conspecific signals the safety of the food. We used safe food preference as putative murine homologue of human trust acquisition, and modeled trust violation (PE) using lithium chloride (LiCl)-induced food aversion after social interaction. In males, results revealed that OT enhanced trust acquisition, whereas both OT and its antagonist CL similarly blocked trust violation learning. None of the manipulations affected female behavior. Our findings highlight the complexities of OT's role in social behavior, emphasizing caution in therapeutic manipulations of this system.

Parenthood status and plasma oxytocin levels predict specific emotion perception abilities

Superior recognition of positive emotional facial expressions compared to negative expressions is well established. However, it is unclear whether this superiority effect differs between non-parents and parents, for whom emotion perception (EP) is an indispensable skill. Although EP has been shown to be modulated by the neuropeptide oxytocin, a central factor in the development of parental care, very little research has addressed the relationship between EP skills, the transition to parenthood, and plasma oxytocin levels. In the present study, we assessed EP abilities with a test battery and measured plasma oxytocin in 77 non-parent and 79 parent couples and applied structural equation modelling to the data. The results showed increased happiness perception abilities in both parents and individuals with elevated oxytocin levels. Furthermore, non-parents showed superior abilities to recognise anger expressions. No significant associations were found regarding the perception of other basic emotion categories or with a general EP factor. The findings are consistent with previous research indicating that elevated oxytocin levels are associated with enhanced EP abilities. They also extend the existing literature by demonstrating that mothers and fathers, regardless of their oxytocin levels, exhibit increased EP superiority.

Neuroimaging and behavioral evidence of sex-specific effects of oxytocin on human sociality

Although the social role of oxytocin came to light due to sex-specific interactions such as mother-offspring bonding, current understanding of sex differences in the effects of oxytocin on human sociality is limited because of the predominance of all-male samples. With the increasing inclusion of females in intranasal oxytocin research, it is now possible to explore such patterns. Neuroimaging studies reveal relatively consistent sex-differential effects of oxytocin on the activation of brain regions associated with processing social stimuli - particularly the amygdala. Findings from behavioral research are varied but suggest that oxytocin more often facilitates social cognition and positive social interactions in males, with context-dependent effects in each sex. We discuss potential biological and psychological mechanisms underlying the reported sex differences, and conclude with considerations for future research and clinical applications of oxytocin.

Maternal antenatal depression, oxytocin, and infant temperament: The roles of ethnicity and adult attachment avoidance

This study examined the associations between maternal depression and oxytocin in pregnancy, caregiving sensitivity and adult attachment style, and infant temperament. One hundred and six women recruited from a public hospital antenatal clinic in Australia, and their infants completed assessments at three time points (Time 1: pregnancy; Time 2: 3-month postpartum; Time 3: 12-month postpartum). Mothers completed self-report questionnaires assessing maternal depression symptom severity at Time 1-3, adult attachment style at Time 2, and infant temperament at Time 3. At Time 1, they also provided a blood sample to assess peripheral oxytocin levels, and at Time 2, participated in a parent-child interaction session, which was later coded for caregiving behavior (sensitivity). Neither maternal depression nor lower levels of oxytocin during pregnancy predicted difficult infant temperament; rather, it was predicted by non-Caucasian ethnicity. When all other variables were free to vary, adult attachment avoidance mediated an association between maternal depression during pregnancy and difficult infant temperament. Results highlight the potential value of interventions focusing on adult attachment insecurity for pregnant women and raise questions about associations between culture/ethnicity and infant temperament.

Physiology of Human Lactation and Strategies to Support Milk Supply for Breastfeeding

Despite advances across the globe in breastfeeding initiation rates, many families continue to report they are not meeting their breastfeeding goals. Concerns about milk supply, infant nutritional intake, and infant weight gain are among the most commonly cited reasons for early breastfeeding cessation. Nurses working with individuals during the perinatal period are uniquely positioned to educate families and offer evidence-based interventions to promote optimal milk supply, infant growth, and maternal mental and physical health. Such interventions include early and frequent skin-to-skin care, emptying of the breast, and professional lactation support. By implementing such evidence-based practices in the first hours after birth and connecting families to lactation support in the first 14 days, nurses can begin to help families achieve their breastfeeding goals.

Infants' salivary oxytocin and positive affective reactions to people

Oxytocin is a neuropeptide positively associated with prosociality in adults. Here, we studied whether infants' salivary oxytocin can be reliably measured, is developmentally stable, and is linked to social behavior. We longitudinally collected saliva from 62 U.S. infants (44 % female, 56 % Hispanic/Latino, 24 % Black, 18 % non-Hispanic White, 11 % multiracial) at 4, 8, and 14 months of age and offline-video-coded the valence of their facial affect in response to a video of a smiling woman. We also captured infants' affective reactions in terms of excitement/joyfulness during a live, structured interaction with a singing woman in the Early Social Communication Scales at 14 months. We detected stable individual differences in infants' oxytocin levels over time (over minutes and months) and in infants' positive affect over months and across contexts (video-based and in live interactions). We detected no statistically significant changes in oxytocin levels between 4 and 8 months but found an increase from 8 to 14 months. Infants with higher oxytocin levels showed more positive facial affect to a smiling person video at 4 months; however, this association disappeared at 8 months, and reversed at 14 months (i.e., higher oxytocin was associated with less positive facial affect). Infant salivary oxytocin may be a reliable physiological measure of individual differences related to socio-emotional development.

Human placental lactogen (human chorionic somatomammotropin) and oxytocin during pregnancy: Individual patterns and associations with maternal-fetal attachment, anxiety, and depression

Previous studies support links among maternal-fetal attachment, psychological symptoms, and hormones during pregnancy and the post-partum period. Other studies connect maternal feelings and behaviors to oxytocin and suggest that an increase in oxytocin during pregnancy may prime maternal-fetal attachment. To date, researchers have not examined a possible association between maternal-fetal attachment with human placental lactogen although animal models are suggestive. In the current study, we sought to describe oxytocin and human placental lactogen levels as related to psychological constructs across pregnancy. Seventy women participated in the study. At each of three time-points (early, mid, and late pregnancy), the women had their blood drawn to assess oxytocin and human placental lactogen levels, and they completed psychological assessments measuring maternal-fetal attachment, anxiety, and depression. Our results indicate that oxytocin levels were statistically similar across pregnancy, but that human placental lactogen significantly increased across pregnancy. Results did not indicate significant associations of within-person (comparing individuals to themselves) oxytocin or human placental lactogen levels with maternal-fetal attachment. Additionally, results did not show between-person (comparing individuals to other individuals) oxytocin or human placental lactogen levels with maternal-fetal attachment. Oxytocin levels were not associated with anxiety; rather the stage of pregnancy moderated the effect of the within-person OT level on depression. Notably, increasing levels of human placental lactogen were significantly associated with increasing levels of both anxiety and depression in between subject analyses. The current study is important because it describes typical hormonal and maternal fetal attachment levels during each stage of pregnancy, and because it suggests an association between human placental lactogen and psychological symptoms during pregnancy. Future research should further elucidate these relationships.

Breast milk oxytocin and s-IgA modulate infant biomarkers and social engagement; The role of maternal anxiety

Breastfeeding has long been known to improve infants' health and mental development and to enhance the mother-infant bond, but much less research focused on the biological composition of breast milk and its associations with the infant's biomarkers and social development. In this exploratory study, we measured oxytocin (OT) and secretory immunoglobulin-A (s-IgA), the most abundant antibody in breast milk, and evaluated their associations with the same biomarkers in infant saliva and, consequently, with infant social engagement behavior. Fifty-five mother-infant dyads were home-visit and OT and s-IgA were assessed from breast milk and from infant saliva before and after a free-play interaction. Infant social behavior was coded offline using the Coding Interactive Behavior (CIB) and maternal anxiety self-reported. A path model revealed that mother's breast milk s-IgA impacted child social engagement via its links with child OT. In parallel, maternal breast milk OT was linked with infant social behavior through its association with the infant's immunity. This path was moderated by maternal anxiety; only in cases of high anxiety breast milk OT was positively connected to infant s-IgA. Our study, the first to measure OT and s-IgA in both breast milk and infant saliva in relation to observed social behavior, underscores the need for much further research on the dynamic interplay between breast milk composition, infant biomarkers, maternal mental health, and infant social outcomes. Results may suggest that biological systems in breast milk integrate to prepare infants to function in their social ecology through bio-behavioral feedback loops that signal the degree of stress in the environment.

Romantic love evolved by co-opting mother-infant bonding

For 25 years, the predominant evolutionary theory of romantic love has been Fisher's theory of independent emotion systems. That theory suggests that sex drive, romantic attraction (romantic love), and attachment are associated with distinct neurobiological and endocrinological systems which evolved independently of each other. Psychological and neurobiological evidence, however, suggest that a competing theory requires attention. A theory of co-opting mother-infant bonding sometime in the recent evolutionary history of humans may partially account for the evolution of romantic love. I present a case for this theory and a new approach to the science of romantic love drawing on human psychological, neurobiological, and (neuro)endocrinological studies as well as animal studies. The hope is that this theoretical review, along with other publications, will generate debate in the literature about the merits of the theory of co-opting mother-infant bonding and a new evolutionary approach to the science of romantic love.