Cortisol, hedonics, and maternal responsiveness in human mothers

The olfactory bulb: A neuroendocrine spotlight on feeding and metabolism

Olfaction is the most ancient sense and is needed for food-seeking, danger protection, mating and survival. It is often the first sensory modality to perceive changes in the external environment, before sight, taste or sound. Odour molecules activate olfactory sensory neurons that reside on the olfactory epithelium in the nasal cavity, which transmits this odour-specific information to the olfactory bulb (OB), where it is relayed to higher brain regions involved in olfactory perception and behaviour. Besides odour processing, recent studies suggest that the OB extends its function into the regulation of food intake and energy balance. Furthermore, numerous hormone receptors associated with appetite and metabolism are expressed within the OB, suggesting a neuroendocrine role outside the hypothalamus. Olfactory cues are important to promote food preparatory behaviours and consumption, such as enhancing appetite and salivation. In addition, altered metabolism or energy state (fasting, satiety and overnutrition) can change olfactory processing and perception. Similarly, various animal models and human pathologies indicate a strong link between olfactory impairment and metabolic dysfunction. Therefore, understanding the nature of this reciprocal relationship is critical to understand how olfactory or metabolic disorders arise. This present review elaborates on the connection between olfaction, feeding behaviour and metabolism and will shed light on the neuroendocrine role of the OB as an interface between the external and internal environments. Elucidating the specific mechanisms by which olfactory signals are integrated and translated into metabolic responses holds promise for the development of targeted therapeutic strategies and interventions aimed at modulating appetite and promoting metabolic health.

Failure to mate enhances investment in behaviors that may promote mating reward and impairs the ability to cope with stressors via a subpopulation of Neuropeptide F receptor neurons

Living in dynamic environments such as the social domain, where interaction with others determines the reproductive success of individuals, requires the ability to recognize opportunities to obtain natural rewards and cope with challenges that are associated with achieving them. As such, actions that promote survival and reproduction are reinforced by the brain reward system, whereas coping with the challenges associated with obtaining these rewards is mediated by stress-response pathways, the activation of which can impair health and shorten lifespan. While much research has been devoted to understanding mechanisms underlying the way by which natural rewards are processed by the reward system, less attention has been given to the consequences of failure to obtain a desirable reward. As a model system to study the impact of failure to obtain a natural reward, we used the well-established courtship suppression paradigm in Drosophila melanogaster as means to induce repeated failures to obtain sexual reward in male flies. We discovered that beyond the known reduction in courtship actions caused by interaction with non-receptive females, repeated failures to mate induce a stress response characterized by persistent motivation to obtain the sexual reward, reduced male-male social interaction, and enhanced aggression. This frustrative-like state caused by the conflict between high motivation to obtain sexual reward and the inability to fulfill their mating drive impairs the capacity of rejected males to tolerate stressors such as starvation and oxidative stress. We further show that sensitivity to starvation and enhanced social arousal is mediated by the disinhibition of a small population of neurons that express receptors for the fly homologue of neuropeptide Y. Our findings demonstrate for the first time the existence of social stress in flies and offers a framework to study mechanisms underlying the crosstalk between reward, stress, and reproduction in a simple nervous system that is highly amenable to genetic manipulation.

Correlates of preconception and pregnancy hair cortisol concentrations

Assessing factors that influence chronic stress biomarkers like hair cortisol concentrations (HCCs) in pregnancy is critical to prevent adverse pregnancy outcomes. Thus, we aimed to identify correlates of HCC preconception and during pregnancy. 2,581 pregnant women participated in the study. HCC was available at four time periods: pre-pregnancy (0-3 months preconception, n = 1,023), and in the first (1-12 weeks, n = 1,734), second (13-24 weeks, n = 1,534), and third (25-36 weeks, n = 835) trimesters. HCC was assessed using liquid chromatography tandem mass spectrometry (LC-MS/MS). Sociodemographic, pregnancy- and hair-related characteristics, and measures of psychosocial stress, were interrogated as potential correlates of HCC. Spearman correlations, paired t-tests, and ANOVA were used to assess differences in log-transformed values of HCC (logHCC) across maternal characteristics. Multivariable linear regressions were used to identify the correlates of HCCs after adjusting for confounders. Mean logHCC values increased across the four prenatal periods (P < 0.001). In multivariable analyses, pre-pregnancy BMI was consistently associated with all HCCs, while gestational age, economic hardship, hair dyeing, and depression, showed time-specific associations with HCC. In conclusion, this study showed evidence of factors influencing HCC levels before and during pregnancy. The most consistent association was seen with pre-pregnancy BMI. Depression was also associated with HCC concentrations.

Increased sensitivity to unpleasant odor following acute psychological stress

Previous studies have reported increased sensitivity to malodor after acute stress in humans. However, it is unclear whether stress-related "hypersensitivity" to odors depends on odor pleasantness. Forty participants (mean age 19.13 ± 1.14 years, 21 men and 19 women) completed a stress (Trier Social Stress Test, TSST) and a control session in randomized order. Detection threshold to three odors varying in pleasantness (pleasant: β-Citronellol; neutral: 2-Heptanol; unpleasant: 4-Methylpentanoic acid), odor discrimination, odor identification, sensitivity to trigeminal odor, and suprathreshold odor perception were assessed after participants' completion of the stress or the control tasks. Salivary cortisol, subjective stress, and heart rate were assessed throughout the experiment. After TSST, participants showed an increased sensitivity for the unpleasant odor. Moreover, there were correlations between stress-related salivary cortisol and the increased sensitivity for the unpleasant odor (r = 0.32, p = 0.05) and the neutral odor (r = 0.34, p < 0.05). Besides, salivary cortisol response was correlated to the increased odor discrimination performance (Δ stress - control) (r = 0.34, p < 0.05). The post-TSST perceived stress was correlated with decreased odor identification and decreased sensitivity to the unpleasant odor. After stress, participants rated lower pleasantness for β-Citronellol than the control condition. Overall, these results suggest the impact of acute psychological stress on odor sensitivity depends on the odor valence, and that the stress-related cortisol responses may play an important role in this effect.

Protein-caloric restriction induced HPA axis activation and altered the milk composition imprint metabolism of weaned rat offspring

OBJECTIVES

Maternal protein-caloric restriction during lactation can malprogram offspring into having a lean phenotype associated with metabolic dysfunction in early life and adulthood. The aim of this study was to investigate the relationships between nutritional stress, maternal behavior and metabolism, milk composition, and offspring parameters. Additionally, we focused on the role of hypothalamus-pituitary-adrenal axis hyperactivation during lactation.

METHODS

Dams were fed a low-protein diet (4% protein) during the first 2 wk of lactation or a normal-protein diet (20% protein) during all lactation. Analyses of dams, milk, and offspring were conducted on postnatal days (PD) 7, 14, and 21.

RESULTS

Body weight and food intake decreased in dams, which was associated with reduced fat pad stores and increased corticosterone levels at PD 14. The stressed low-protein diet dams demonstrated alterations in behavior and offspring care. Despite nutritional deprivation, dams adapted their metabolism to provide adequate energy supply through milk; however, we demonstrated elevated corticosterone and total fat levels in milk at PD 14. Male offspring also showed increased corticosterone at PD 7, associated with a lean phenotype and alterations in white and brown adipose tissue morphology at PD 21.

CONCLUSION

Exposure to protein-caloric restriction diet of dams during lactation increased the glucocorticoid levels in dams, milk, and offspring, which is associated with alterations in maternal behavior and milk composition. Thus, glucocorticoids and milk composition may play an important role in metabolic programming induced by maternal undernutrition.

Hormonal and behavioral responses to an infant simulator in women with and without children

We investigated the impact of maternal status on hormonal reactivity and behavioral responses to an infant simulator in 117 women (54 primiparous, 63 nulliparous). The amount of affectionate touch and motherese were analyzed as behavioral measures of caregiving. Saliva was collected before and 10 min after interaction with the infant simulator to analyze oxytocin, testosterone, cortisol, and estradiol levels. Nulliparous women also provided information about their fertility motivation. Linear mixed models indicated that greater use of affectionate touch was associated with lower overall testosterone levels. Cortisol decreased in response to the interaction in both groups. In the primiparous group, the amount of affectionate touch associated inversely with cortisol levels, whereas in the nulliparous group such association was not found. Oxytocin or estradiol reactivity to the simulator did not differ between the groups, nor were these hormones associated with behavior. Higher fertility motivation in nulliparous women was related to more motherese, and lower testosterone levels. Our results indicate that the simulator elicits hormonal reactivity both in mothers and nonmothers, but the patterns of associations between caregiving behavior and hormonal levels may be partially different. These results encourage using the infant simulator to explore hormonal processes related to the transition to parenthood.

Residential greenness and hair cortisol levels during the first trimester of pregnancy

BACKGROUND AND AIM

Studies have shown that increased maternal cortisol level is associated with child adverse health outcomes. Hair cortisol (HC) is suitable for assessing long-term circulating cortisol concentration. Only two previous studies reported beneficial associations between cortisol and residential greenness during pregnancy and no study focused on the first trimester. Our aim was to evaluate the association between residential greenness and first trimester HC levels among pregnant women in Israel.

METHODS

Women were recruited during second and third trimesters. Hair samples were collected from the scalp and retrospective HC levels during the first trimester were quantified for 217 women. HC levels were natural log transformed and outliers were excluded. Based on geocoded birth address, small area sociodemographic status (SES) and mean residential surrounding greenness were calculated using high-resolution satellite-based Normalised Difference Vegetation Index (NDVI) data at 100, 300 and 500-m buffers in a cross-sectional approach. In addition, longitudinal exposure to mean greenness during a week preconception and during the first trimester were calculated. Missing covariates were imputed and linearity of the associations were evaluated. Generalized linear models were used to estimate the crude and adjusted associations controlled for the relevant covariates.

RESULTS

After exclusion of outliers, for 211 women, crude and adjusted beneficial associations between exposure to higher mean NDVI and HC levels were observed for all the exposure measures. An increase in 1 interquartile range of greenness (100 m buffer) was associated with a statistically significant lower estimated natural log mean HC level (-0.27 95% CI: -0.44; -0.11). The associations were robust to adjustment for covariates. The findings were consistent for different buffers, for the longitudinal approach, when all observations were included in the analysis and slightly stronger associations were observed for women with addresses geocoded at the home or street level. For most of the exposure measures, stronger associations were observed among those of lower sociodemographic status.

CONCLUSION

Our findings that more greenness associated with reduced maternal cortisol levels measured in the hair during the first trimester, could have substantial implications for urban planners and public health professional. If our observations will be replicated, it may present a useful avenue for public-health intervention to promote health through the provision of greenness exposure during early pregnancy, specifically to disadvantage populations.

Maternal separation: Does it hold the potential to model consequences of postpartum depression?

The postpartum period is a sensitive time where women are especially vulnerable to develop postpartum depression (PPD), with 10%-15% of women affected. This review investigates whether the maternal separation (MS) paradigm in rodents holds the potential to help to understand mothers suffering from PPD. MS is a well-established stress model to investigate effects on infants, whereas effects on the dam are often overlooked. The database PubMed was searched for studies investigating effects of daily MS within the first weeks after parturition on dams in rats and mice and compared to findings in PPD mothers. MS was categorized as brief MS (5-45 min) with or without handling of pups and long MS (3-4 h and longer). MS alters maternal care, depressive-like behavior, anxiety, and aggression; leads to alterations in neuronal gene expression; and affects hormone and neurotransmitter levels similar to observations in PPD patients. Even though there are disparities between human and rodent mothers, with some results differing in directionality, as well as the reason for separation (self-induced in PPD, externally induced in MS), the overall effects found on neurobiological, hormonal, and behavioral levels mostly coincide. Thus, the MS paradigm can add relevant knowledge to existing PPD animal models, further advancing the study of PPD.

Social Network and Behavioral Synchrony Influences On Maternal and Infant Cortisol Response

This study examined the contributions of mothers' social network stability and mother-infant behavioral synchrony on cortisol response in infants and their mothers during separation. The quality and stability of mothers' social network system and mother-infant bond have both been shown to affect infant neuroendocrine response. Yet, no studies have directly addressed how these two forms of social relationships might differentially affect infants' and mothers' neuroendocrine responses during separation. First-time mothers (N = 133) and their 3-month-old infants participated in the study. Maternal social network stability, mother-infant behavioral synchrony, and mother and infant cortisol response during an infant challenge task were assessed. Behavioral synchrony accounted for significant variance in infants' cortisol response, and after adjusting for synchrony, mothers' network stability measures did not explain variance in infant cortisol. Social network stability, but not synchrony, accounted for significant variance in mothers' cortisol response. These results demonstrate that, when mothers and infants experience brief separation, the quality of their bond is associated with a lower stress response for infants; but for mothers, it is the longevity of her social relationships outside of the mother-infant relationship context that is associated with her lower stress response.

Non-physiological and Physiological Delivery Method: Comparison of Maternal Attachment Behaviors and Anxiety

Introduction: Attachment is a stable connection or emotional knot between two individuals as one of the parties tries to maintain this connection. Delivery time as a turning point between two stages of attachment is very important. Methods: In a descriptive-analytical study based on specific inclusion criteria, 262 pregnant women were selected in the age range of 15-45 years old and the gestational age of 37 to 42 weeks who were candidates for physiological or non-physiological delivery. After obtaining written consent forms, the demographic information questionnaire was given to the participants. One hour after delivery, the attachment questionnaire was completed by the researcher in the postpartum ward. Also, the Spielberg anxiety inventory was completed up to 1 hour after delivery. Independent sample t test was used to compare the results between the two groups. Data were analyzed by SPSS software version 21. Results: The participants in the physiological delivery group showed more positive attachment behaviors in comparison with the other group. In all three dimensions of attachment (emotional, contiguous, and caring behavior), physiological delivery showed higher scores than the other group. Also in non-physiological delivery group, the participants had experienced higher levels of anxiety and the differences between the groups were not significant. Conclusion: Results of the current study indicated that mothers engaged in physiological delivery had higher scores in mother to child attachment behaviors. It means they are more successful than the non-physiological delivery group in getting attached to their babies.

Progesterone - Friend or foe?

Estradiol is the "prototypic" sex hormone of women. Yet, women have another sex hormone, which is often disregarded: Progesterone. The goal of this article is to provide a comprehensive review on progesterone, and its metabolite allopregnanolone, emphasizing three key areas: biological properties, main functions, and effects on mood in women. Recent years of intensive research on progesterone and allopregnanolone have paved the way for new treatment of postpartum depression. However, treatment for premenstrual syndrome and premenstrual dysphoric disorder as well as contraception that women can use without risking mental health problems are still needed. As far as progesterone is concerned, we might be dealing with a two-edged sword: while its metabolite allopregnanolone has been proven useful for treatment of PPD, it may trigger negative symptoms in women with PMS and PMDD. Overall, our current knowledge on the beneficial and harmful effects of progesterone is limited and further research is imperative.

Mothering revisited: A role for cortisol?

This selective review first describes the involvement of the maternal hypothalamic-pituitary-adrenal (HPA) axis during pregnancy and the postpartum period, and the relation between peripartum HPA axis function and maternal behavior, stress reactivity and emotional dysregulation in human mothers. To provide experimental background to this correlational work, where helpful, animal studies are also described. It then explores the association between HPA axis function in mothers and their infants, under ongoing non-stressful conditions and during stressful challenges, the moderating role of mothers' sensitivity and behavior in the mother-child co-regulation and the effects of more traumatic risk factors on these relations. The overarching theme being explored is that the HPA axis - albeit a system designed to function during periods of high stress and challenge - also functions to promote adaptation to more normative processes, shown in the new mother who experiences both high cortisol and enhanced attraction and attention to and recognition of, their infants and their cues. Hence the same HPA system shows positive relations with behavior at some time points and inverse ones at others. However, the literature is not uniform and results vary widely depending on the number, timing, place, and type of samplings and assessments, and, of course, the population being studied and, in the present context, the state, the stage, and the stress levels of mother and infant.

Birth of a Father: Fathering in the First 1,000 Days

As a result of societal changes, fathers participate more actively in child care than they used to. In this article, we propose a context-dependent biobehavioral model of emergent fatherhood in which sociocultural, behavioral, hormonal, and neural factors develop and interact during the first 1,000 days of fatherhood. Sociocultural factors, including different expectations of fathers and varying opportunities for paternal caregiving through paid paternal leave, influence paternal involvement. Levels of hormones (e.g., testosterone, vasopressin, oxytocin, cortisol) predict fathers' parenting behaviors, and involvement in caregiving in turn affects their hormones and brain responses to infant stimuli. The birth of the first child marks the transition to fatherhood and may be a critical period in men's lives, with a smoother transition to fatherhood predicting more optimal involvement by fathers in subsequent years. A focus on prenatal and early postnatal fathering may pave the way for developing interventions that effectively support fathering during pregnancy and in the first years of their children's lives.

Endocrine Regulations in Human-Dog Coexistence through Domestication

Endocrine system regulation is important for the maintenance of homeostasis; it controls hormonal functions in complex physiology and behavior and adaptations to social environments. Evidence indicates that for more than 35 000 years, dogs (Canis familiaris) have been domesticated through living with humans. For example, they have acquired human-like social skills, such as eye gazing and pointing gestures. These unique behaviors are, at least partially, regulated by hormones and are thought to have been genetically altered throughout domestication. Glucocorticoids affect social tolerance, while oxytocin facilitates social coordination and familiarity between individuals. We review historical and recent literature to facilitate an understanding of the roles of glucocorticoid and oxytocin functions in the human-canine coexistence dynamic established during domestication.

Resilience priming: Translational models for understanding resiliency and adaptation to early life adversity

Despite the increasing attention to early life adversity and its long-term consequences on health, behavior, and the etiology of neurodevelopmental disorders, our understanding of the adaptations and interventions that promote resiliency and rescue against such insults are underexplored. Specifically, investigations of the perinatal period often focus on negative events/outcomes. In contrast, positive experiences (i.e. enrichment/parental care//healthy nutrition) favorably influence development of the nervous and endocrine systems. Moreover, some stressors result in adaptations and demonstrations of later-life resiliency. This review explores the underlying mechanisms of neuroplasticity that follow some of these early life experiences and translates them into ideas for interventions in pediatric settings. The emerging role of the gut microbiome in mediating stress susceptibility is also discussed. Since many negative outcomes of early experiences are known, it is time to identify mechanisms and mediators that promote resiliency against them. These range from enrichment, quality parental care, dietary interventions and those that target the gut microbiota.

Fathers' cortisol and testosterone in the days around infants' births predict later paternal involvement

Human paternal behavior is multidimensional, and extant research has yet to delineate how hormone patterns may be related to different dimensions of fathering. Further, although studies vary in their measurement of hormones (i.e., basal or reactivity), it remains unclear whether basal and/or reactivity measures are predictive of different aspects of men's parenting. We examined whether men's testosterone and cortisol predicted fathers' involvement in childcare and play with infants and whether fathers' testosterone and cortisol changed during fathers' first interaction with their newborn. Participants were 298 fathers whose partners gave birth in a UNICEF-designated "baby-friendly" hospital, which encourages fathers to hold their newborns 1 h after birth, after mothers engage in skin-to-skin holding. Salivary testosterone and cortisol were measured before and after fathers' first holding of their newborns. Basal and short-term changes in cortisol and testosterone were analyzed. Fathers were contacted 2-4 months following discharge to complete questionnaires about childcare involvement. Fathers' cortisol decreased during the time they held their newborns on the birthing unit. Fathers' basal testosterone in the immediate postnatal period predicted their greater involvement in childcare. Both basal and reactivity cortisol predicted fathers' greater involvement in childcare and play. Results suggest that reduced basal testosterone is linked with enhanced paternal indirect and direct parenting effort months later, and that higher basal cortisol and increases in cortisol in response to newborn interaction are predictive of greater paternal involvement in childcare and play, also months later. Findings are discussed in the context of predominating theoretical models on parental neuroendocrinology.

The HPA Axis During the Perinatal Period: Implications for Perinatal Depression

The transition to motherhood is characterized by some of the most pronounced endocrine changes a woman will experience in her lifetime. Unfortunately, matrescence is also a time in a woman's life when she is most susceptible to mental illness such as perinatal depression. A growing body of research has aimed to determine how key endocrine systems, such as the hypothalamic-pituitary-adrenal (HPA) axis, are involved in the dysregulation of perinatal mental health. However, very little research has consistently linked perinatal changes in the HPA axis with maternal mental illness. Therefore, the aims of this mini review are to: (i) clearly summarize the normative changes in the HPA axis that occur during pregnancy and the postpartum period; (ii) summarize what we know about the HPA axis in perinatal depression, and (iii) propose key areas for future research. Understanding physiological biomarkers that can predict which women are at risk for perinatal mood disorders will lead to better tools for treating, and ultimately preventing, these debilitating disorders, improving the health of mother, child, and family.

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.

Exposure to traumatic events in childhood predicts cortisol production among high risk pregnant women

Childhood exposure to traumatic events has a profound and disruptive impact on mental and physical health, including stress physiology. In the current study, we evaluate 90 pregnant women at risk for preterm delivery and assess the association between history of exposure to traumatic events and hair cortisol concentrations, an integrated measure of cortisol production. Exposure to more traumatic events in childhood and in adulthood independently predicted elevated hair cortisol concentrations in pregnancy. Notably, the impact of childhood exposure to traumatic events remained after accounting for more proximal traumatic events in adulthood. Further, there was a significant interaction between childhood and adult exposures. Traumatic experiences in adulthood were more strongly associated with hair cortisol concentrations among mothers with a history of greater childhood trauma. Findings suggest that not only do proximal adult exposures impact HPA-axis functioning during pregnancy, but that childhood traumatic experiences have persisting consequences for HPA-axis functioning during pregnancy. Maternal HPA-axis dysregulation in pregnancy has consequences for both maternal health and for fetal development. Therefore, we consider prenatal maternal HPA-axis functioning as a potential biological pathway underlying intergenerational consequences of childhood trauma.

Mother-child bonding is associated with the maternal perception of the child's body odor

Mothers can recognize the odor of their baby and typically adore this odor. In line with this observation, infant body odors activate reward-related brain areas in the mothers. In some mother-child-dyads however, the mutual bond is impaired and mothers have trouble engaging in interaction with their child. We aimed to examine how mothers with bonding difficulties perceive their child's body odor. In total, 75 mothers of babies aged 0-12 months were examined: Twenty-five of those were recruited in a psychosomatic day hospital ward, which is specialized for mother-child bonding disorders. Fifty age-matched healthy women and their babies served as controls. Body odor samples of each baby were collected from bodysuits in a highly standardized procedure. Thereafter, each mother rated the samples of her own and two other infants in a blind and randomized design. In addition, general olfactory function in terms of threshold and identification ability was tested and the mother reported the bonding to her baby in a standardized questionnaire. Healthy mothers showed a clear preference of their own compared to odors of other infant's, while mothers with bonding difficulties did not. Furthermore, the degree of preference was negatively correlated to self-reported bonding difficulties. Mothers with bonding difficulties could not identify their own infant's odor above chance, while control mothers could. Both groups did not differ in general olfactory function. We assume that reduced close body contact and interaction time associated with bonding difficulties may lead to reduced exposure and hinder the recognition of the infantile body odor. Within a vicious cycle, a reduced hedonic experience smelling their own baby may prevent women from deliberately approaching the baby. Thus, the positive and bond-building consequences of bodily and sensory interaction cannot unfold. As the baby's odor is normally perceived as very pleasant and rewarding, the conscious perception of the infantile body odor may be an additive therapeutic approach for mothers with bonding difficulties.

Associations between glucocorticoids and sociality across a continuum of vertebrate social behavior

The causes and consequences of individual differences in animal behavior and stress physiology are increasingly studied in wild animals, yet the possibility that stress physiology underlies individual variation in social behavior has received less attention. In this review, we bring together these study areas and focus on understanding how the activity of the vertebrate neuroendocrine stress axis (HPA-axis) may underlie individual differences in social behavior in wild animals. We first describe a continuum of vertebrate social behaviors spanning from initial social tendencies (proactive behavior) to social behavior occurring in reproductive contexts (parental care, sexual pair-bonding) and lastly to social behavior occurring in nonreproductive contexts (nonsexual bonding, group-level cooperation). We then perform a qualitative review of existing literature to address the correlative and causal association between measures of HPA-axis activity (glucocorticoid levels or GCs) and each of these types of social behavior. As expected, elevated HPA-axis activity can inhibit social behavior associated with initial social tendencies (approaching conspecifics) and reproduction. However, elevated HPA-axis activity may also enhance more elaborate social behavior outside of reproductive contexts, such as alloparental care behavior. In addition, the effect of GCs on social behavior can depend upon the sociality of the stressor (cause of increase in GCs) and the severity of stress (extent of increase in GCs). Our review shows that the while the associations between stress responses and sociality are diverse, the role of HPA-axis activity behind social behavior may shift toward more facilitating and less inhibiting in more social species, providing insight into how stress physiology and social systems may co-evolve.

Maternal programming: Application of a developmental psychopathology perspective

The fetal phase of life has long been recognized as a sensitive period of development. Here we posit that pregnancy represents a simultaneous sensitive period for the adult female with broad and persisting consequences for her health and development, including risk for psychopathology. In this review, we examine the transition to motherhood through the lens of developmental psychopathology. Specifically, we summarize the typical and atypical changes in brain and behavior that characterize the perinatal period. We highlight how the exceptional neuroplasticity exhibited by women during this life phase may account for increased vulnerability for psychopathology. Further, we discuss several modes of signaling that are available to the fetus to affect maternal phenotypes (hormones, motor activity, and gene transfer) and also illustrate how evolutionary perspectives can help explain how and why fetal functions may contribute to maternal psychopathology. The developmental psychopathology perspective has spurred advances in understanding risk and resilience for mental health in many domains. As such, it is surprising that this major epoch in the female life span has yet to benefit fully from similar applications.

The role of breastfeeding in the association between maternal and infant cortisol attunement in the first postpartum year

AIM

To explore the role of breastfeeding as a possible link between maternal and infant cortisol attunement across the first postpartum year.

METHODS

Mothers (n = 93) provided salivary samples for cortisol levels over a two-day period during mid-pregnancy and at three, six and 12 months and infants at six and 12 months postpartum. Breastfeeding status was established at these same time points.

RESULTS

Among breastfeeding mothers, positive correlations were found between maternal cortisol levels during pregnancy and at three months postpartum and infant cortisol at six or 12 months postpartum. Among nonbreastfeeding mothers, these same maternal and infant cortisol relations were inverse and less pronounced. Further, in breastfeeding mothers, the relationship between maternal prenatal cortisol and infant cortisol at 12 months was mediated through maternal cortisol at three months postpartum.

CONCLUSION

These results suggest that maternal cortisol levels are positively associated with cortisol levels of the infant, among mothers who breastfeed. This relationship persists over a one-year period.

Oxytocin and Human Sensitive and Protective Parenting

In this chapter we review the evidence for the role of oxytocin in parenting, and discuss some crucial but outstanding questions. This is not meant to be a comprehensive review of all studies on oxytocin and parenting in general. Instead, special attention will be paid to a dimension of parenting that has been largely neglected in behavioral and neurobiological research on parental caregiving, namely protection. Parental protection has received considerable attention in animal research but, despite its evolutionary importance, not in studies on humans. It is argued that oxytocin may have specific significance for the protective dimension of parenting. The effects of exogenous oxytocin may be dependent not only on contextual factors, but also on personal characteristics, most notably gender, on endogenous levels of oxytocin, and on early childhood experiences. Examining the contextual, personal, hormonal, neural, genetic, and behavioral mechanisms of protective parenting in tandem is essential for the development of a comprehensive theory of protective parenting, and for the identification of "biomarkers" for insensitive and unprotective parenting that should be taken into account in preventive parenting interventions.

Sex differences in depression during pregnancy and the postpartum period

Women have a lifetime risk of major depression double that of men but only during their reproductive years. This sex difference has been attributed partially to activational effects of female sex steroids and also to the burdens of pregnancy, childbirth, and parenting. Men, in contrast, have a reproductive period difficult to delineate, and research on the mental health of men has rarely considered the effects of fatherhood. However, the couple goes through a number of potentially stressing events during the reproductive period, and both mothers and fathers are at risk of developing peripartum depression. This Review discusses the literature on maternal and paternal depression and the endocrine changes that may predispose a person to depression at this stage of life, with specific focus on the hypothalamus–pituitary axis, oxytocin, and testosterone levels in men. Important findings on sex differences in the neural correlates of maternal and paternal behavior have emerged, highlighting the relevance of the emotional brain in mothers and the sociocognitive brain in fathers and pointing toward the presence of a common parents' brain. Additionally, sex differences in neurogenesis and brain plasticity are described in relation to peripartum depression. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Sex differences in cortisol's regulation of affiliative behavior

A contribution to a special issue on Hormones and Human Competition. A stress perspective is used to illuminate how competitive defeat and victory shape biology and behavior. We report a field study examining how change in cortisol following perceived defeat (vs. victory) in a competition-in this case, a dog agility competition-relates to affiliative behavior. Following competition, we measured cortisol change and the extent to which dog handlers directed affiliative behaviors toward their dogs. We found striking sex differences in affiliation. First, men were more affiliative toward their dogs after victory, whereas women were more affiliative after defeat. Second, the greater a female competitor's increase in cortisol, the more time she spent affiliating with her dog, whereas for men, the pattern was the exact opposite: the greater a male competitor's increase in cortisol, the less time he spent affiliating with his dog. This pattern suggests that, in the wake of competition, men and women's affiliative behavior may serve different functions-shared celebration for men; shared consolation for women. These sex differences show not only that men and women react very differently to victory and defeat, but also that equivalent changes in cortisol across the sexes are associated with strikingly different behavioral consequences for men and women.

Endocrinology of human female sexuality, mating, and reproductive behavior

Hormones orchestrate and coordinate human female sexual development, sexuality, and reproduction in relation to three types of phenotypic changes: life history transitions such as puberty and childbirth, responses to contextual factors such as caloric intake and stress, and cyclical patterns such as the ovulatory cycle. Here, we review the endocrinology underlying women's reproductive phenotypes, including sexual orientation and gender identity, mate preferences, competition for mates, sex drive, and maternal behavior. We highlight distinctive aspects of women's sexuality such as the possession of sexual ornaments, relatively cryptic fertile windows, extended sexual behavior across the ovulatory cycle, and a period of midlife reproductive senescence-and we focus on how hormonal mechanisms were shaped by selection to produce adaptive outcomes. We conclude with suggestions for future research to elucidate how hormonal mechanisms subserve women's reproductive phenotypes.

The Neurobiology of Postpartum Anxiety and Depression

Ten to twenty percent of postpartum women experience anxiety or depressive disorders, which can have detrimental effects on the mother, child, and family. Little is known about the neural correlates of these affective disorders when they occur in mothers, but they do have unique neural profiles during the postpartum period compared with when they occur at other times in a woman's life. Given that the neural systems affected by postpartum anxiety and depression overlap and interact with the systems involved in maternal caregiving behaviors, mother-infant interactions are highly susceptible to disruption. Thus, there is an intricate interplay among maternal mental health, the mother-infant relationship, and the neurobiological mechanisms mediating them that needs to be the focus of future study.

The Impact of Stress on Odor Perception

The olfactory system and emotional systems are highly intervened and share common neuronal structures. The current study investigates whether emotional (e.g., anger and fear) and physiological (saliva cortisol) stress responses are associated with odor identification ability and hedonic odor judgments (intensity, pleasantness, and unpleasantness). Nineteen men participated in the modified Trier Social Stress Test (TSST) and a control session (cycling on a stationary bike). The physiological arousal was similar in both sessions. In each session, participants' odor identification score was assessed using the University of Pennsylvania Smell Identification Test, and their transient mood was recorded on the dimensions of valence, arousal, anger, and anxiety. Multivariate regression analyses show that an increase of cortisol in the TSST session (as compared with the control session) is associated with better odor identification performance (β = .491) and higher odor intensity ratings (β = .562). However, increased anger in the TSST session (as compared with the control session) is associated with lower odor identification performance (β = -.482). The study shows divergent effects of the emotional and the physiological stress responses, indicating that an increase of cortisol is associated with better odor identification performance, whereas increased anger is associated with poorer odor identification performance.

Do women tend while men fight or flee? Differential emotive reactions of stressed men and women while viewing newborn infants

Infant care often is carried out under stressful circumstances. Little is known about differences in caretaking motivation between men and women under stress. In the present study, stress was induced in 40 participants (21 women, 19 men) by means of the cold pressor stress test, 40 (22 women, 18 men) serving as controls. Participants then rated their urge to care for newborn infants shown on 20 short video clips. The infants in the videos were either crying (N=10) or were showing typical neonatal facial movements (N=10). Skin conductance was obtained while participants viewed the videos and salivary cortisol was measured to capture stress responses. We found sex differences in caretaking motivation, such that stress led to decreased caretaking motivation in men but not in women. Furthermore, stressed men elicited a stronger skin conductance change while viewing infant videos than stressed women. These findings provide further evidence for differential stress reactions in men and women and may have crucial implications for parental care.

The neurobiology of parenting: A neural circuit perspective

Social interactions are essential for animals to reproduce, defend their territory, and raise their young. The conserved nature of social behaviors across animal species suggests that the neural pathways underlying the motivation for, and the execution of, specific social responses are also maintained. Modern tools of neuroscience have offered new opportunities for dissecting the molecular and neural mechanisms controlling specific social responses. We will review here recent insights into the neural circuits underlying a particularly fascinating and important form of social interaction, that of parental care. We will discuss how these findings open new avenues to deconstruct infant-directed behavioral control in males and females, and to help understand the neural basis of parenting in a variety of animal species, including humans. Please also see the video abstract here.

The endocrinology of human caregiving and its intergenerational transmission

Variation in the quality of parental care has a tremendous impact on a child's social–emotional development. Research investigating the predictors of this variability in human caregiving behavior has mostly focused on learning mechanisms. Evidence is currently accumulating for the complementary underlying role of steroid hormones and neuropeptides. An overview is provided of the hormones and neuropeptides relevant for human caregiving behavior. Then the developmental factors are described that stimulate variability in sensitivity to these hormones and neuropeptides, which may result in variability in the behavioral repertoire of caregiving. The role of genetic variation in neuropeptide and steroid receptors, the role of testosterone and oxytocin during fetal development and parturition, and the impact of experienced caregiving in childhood on functioning of the neuroendocrine stress and oxytocin system are discussed. Besides providing a heuristic framework for further research on the ontogenetic development of human caregiving, a neuroendocrine model is also presented for the intergenerational transmission of caregiving practices. Insight into the underlying biological mechanisms that bring about maladaptive caregiving behavior, such as neglect and insensitive parenting, will hopefully result in more efficient approaches to reduce the high prevalence of such behavior and to minimize the impact on those affected.

Maternal anxiety and physiological reactivity as mechanisms to explain overprotective primiparous parenting behaviors

In this study, we sought to determine whether the affective and physiological experience of primiparous, or first-time, motherhood is distinct from multiparous motherhood, how the child's level of inhibited temperament impacts it, and if such a temperament results in overprotective parenting behaviors. A total of 117 mothers and their 24-month-old toddlers participated in novelty tasks designed to elicit parenting behaviors and toddler's typical fear reactions. Mothers also completed a battery of questionnaires. Results suggest that primiparous mothers experienced more worry, which was associated with increased overprotective parenting behaviors. Primiparous mothers also demonstrated greater physiological (i.e., cortisol) reactivity while watching their first-born children interact with novel stimuli, but how this related to overprotective parenting was dependent on the child's level of inhibition. Specifically, primiparous mothers displayed more cortisol reactivity with their uninhibited toddlers, which indirectly linked parity to less overprotective parenting behaviors. Primiparous mothers of highly inhibited toddlers displayed greater overprotective parenting behaviors, independent of maternal cortisol reactivity. The results indicate that the transition to motherhood is a unique experience associated with greater worry and physiological reactivity and is meaningfully influenced by the toddler's temperament. Distinctions in both observed and self-reported overprotective parenting are evident through considering the dynamic interaction of these various aspects. (PsycINFO Database Record

Psychobiological influences on maternal sensitivity in the context of adversity

This study evaluated prospective longitudinal relations among an index of poverty-related cumulative risk, maternal salivary cortisol, child negative affect, and maternal sensitivity across the first 2 postpartum years. Participants included 1,180 biological mothers residing in rural and predominantly low-income communities in the United States. Multilevel growth curve analyses indicated that an index of cumulative risk was positively associated with maternal cortisol across the postpartum (study visits occurring at approximately 7, 15, and 24 months postpartum) over and above effects for African American ethnicity, time of day of saliva collection, age, parity status, having given birth to another child, contraceptive use, tobacco smoking, body mass index, and breastfeeding. Consistent with a psychobiological theory of mothering, maternal salivary cortisol was negatively associated with maternal sensitivity observed during parent-child interactions across the first 2 postpartum years over and above effects for poverty-related cumulative risk, child negative affect, as well as a large number of covariates associated with cortisol and maternal sensitivity. Child negative affect expressed during parent-child interactions was negatively associated with observed maternal sensitivity at late (24 months) but not early time points of observation (7 months) and cumulative risk was negatively associated with maternal sensitivity across the postpartum and this effect strengthened over time. Results advance our understanding of the dynamic, transactional, and psychobiological influences on parental caregiving behaviors across the first 2 postpartum years. (PsycINFO Database Record

Biological Bases of Maternal Attachment

In recent years, there has been growing interest in investigating the processes affecting caregiving behavior. Recent studies of human and nonhuman primates have suggested that hormones can account, at least in part, for changes in caregiving motivation during pregnancy and the postpartum period and for variability in caregiving motivation and behavior among individuals. Although hormones may not be the primary determinants of caregiving, future research cannot afford to overlook the contribution that biological processes can make to normative and pathological attachment and parenting.

Child Odors and Parenting: A Survey Examination of the Role of Odor in Child-Rearing

Parental caregiving is critical for the survival of our young and continuation of our species. In humans, visual and auditory signals from offspring have been shown to be potent facilitators of parenting. However, whether odors emitted by our young also influence human parenting remains unclear. To explore this, we conducted a series of questionnaire surveys targeting parents with children under 6 years old. First, we collected episodes on experiencing odors/sniffing various parts of a child’s body (n = 507). The prevalence of experiencing events described in those episodes was examined in a separate survey (n = 384). Based on those results, the Child Odor in Parenting scale (COPs) was developed, and subsequently used in the main survey (n = 888). We found COPs to have adequate content validity, concurrent validity, and reliability. Responses to the COPs demonstrated that parents, especially mothers with infants, are aware of odors from their offspring, and actively seek them in daily child-rearing. The factor structure and content of the COPs items indicated that child odors have both affective and instrumental roles. Affective experiences induce loving feeling and affectionate sniffing, while instrumental experiences pertain to specific hygienic needs. The head was the most frequent source of affective experiences, and the child’s bottom of instrumental. Each was experienced by more than 90% of the mothers with a child below 1 year of age. Affective experiences significantly declined as the child grew older, possibly associated with the decline of physical proximity between parents and child. This age-related decline was not prominent for instrumental experiences, except for the bottom, which significantly declined after 3 years of age. The present findings suggest that child odors play roles in human parenting, and that their nature and significance change during the course of a child’s development.

Breastfeeding, Bed-Sharing, and Maternal Cortisol

Prior studies have found that close mother-child sleep proximity helps increase rates of breastfeeding, and breastfeeding itself is linked to better maternal and infant health. In this study, we examine whether breastfeeding and infant bed-sharing are related to daily rhythms of the stress-responsive hormone cortisol. We found that bed-sharing was related to flatter diurnal cortisol slopes, and there was a marginal effect for breastfeeding to predict steeper cortisol slopes. Furthermore, mothers who breastfeed but do not bed-share had the steepest diurnal cortisol slopes, whereas mothers who bed-shared and did not breastfeed had the flattest slopes (P < .05). These results were significant after controlling for subjective sleep quality, perceived stress, depression, socioeconomic status, race, and maternal age. Findings from this study indicate that infant parenting choices recommended for infants (breastfeeding and separate sleep surfaces for babies) may also be associated with more optimal stress hormone profiles for mothers.

Differences in HPA axis reactivity to intimacy in women with and without histories of sexual trauma

BACKGROUND

Sexual trauma can lead to longstanding effects on individuals' intimacy functioning. The current study aimed to assess hypothalamic pituitary adrenal (HPA) axis functioning (i.e., cortisol reactivity) prior to (-5min), during (+15, +30, +45min), and following (+60min) an experimental manipulation of emotional closeness in a sample of women survivors of sexual trauma with varying levels of posttraumatic stress disorder (PTSD) symptomatology versus controls.

METHODS

Participants included 50 women, which were divided into 2 groups on the basis of a structured clinical interview: 26 women with a history of sexual trauma with and without PTSD (sexual trauma group), and 24 women without a history of sexual trauma or PTSD (controls). Participants came into the lab and participated in a 45min emotional closeness exercise with a male confederate and completed self-report questionnaires of closeness, state anxiety/depression, and cortisol assays at the aforementioned time points.

RESULTS

Women with a history of sexual trauma exhibited a blunted cortisol response and greater anxious mood in reaction to the intimacy induction task compared to controls. Results also demonstrated that, unexpectedly, PTSD symptom severity scores among sexual trauma survivors were not associated with differential cortisol responding to the task compared to controls.

CONCLUSIONS

Adaptive responses to stress are characterized by a relatively rapid cortisol increase followed by a steady decline. The results of this study demonstrated that women with a history of sexual trauma, in contrast, displayed a blunted cortisol response to an intimacy induction task. Both controls and women with a history of sexual trauma reported increased feelings of closeness to the male confederate in response to the intimacy induction task, suggesting that survivors were able to achieve similar adaptive feelings of intimacy when provided with the right conditions.

Affective changes during the postpartum period: Influences of genetic and experiential factors

This article is part of a Special Issue "Parental Care". The postpartum period involves some truly transformational changes in females' socioemotional behaviors. For most female laboratory rodents and women, these changes include an improvement in their affective state, which has positive consequences for their ability to sensitively care for their offspring. There is heterogeneity among females in the likelihood of this positive affective change, though, and some women experience elevated anxiety or depression (or in rodents anxiety- or depression-related behaviors) after giving birth. We aim to contribute to the understanding of this heterogeneity in maternal affectivity by reviewing selected components of the scientific literatures on laboratory rodents and humans examining how mothers' physical contact with her infants, genetics, history of anxiety and depression and early-life and recent-life experiences contribute to individual differences in postpartum affective states. These studies together indicate that multiple biological and environmental factors beyond female maternal state shape affective responses during the postpartum period, and probably do so in an interactive manner. Furthermore, the similar capacity of some of these factors to modulate anxiety and depression in human and rodent mothers suggests cross-species conservation of mechanisms regulating postpartum affectivity.

Postpartum depression: Etiology, treatment and consequences for maternal care

This article is part of a Special Issue "Parental Care". Pregnancy and postpartum are associated with dramatic alterations in steroid and peptide hormones which alter the mothers' hypothalamic pituitary adrenal (HPA) and hypothalamic pituitary gonadal (HPG) axes. Dysregulations in these endocrine axes are related to mood disorders and as such it should not come as a major surprise that pregnancy and the postpartum period can have profound effects on maternal mood. Indeed, pregnancy and postpartum are associated with an increased risk for developing depressive symptoms in women. Postpartum depression affects approximately 10-15% of women and impairs mother-infant interactions that in turn are important for child development. Maternal attachment, sensitivity and parenting style are essential for a healthy maturation of an infant's social, cognitive and behavioral skills and depressed mothers often display less attachment, sensitivity and more harsh or disrupted parenting behaviors, which may contribute to reports of adverse child outcomes in children of depressed mothers. Here we review, in honor of the "father of motherhood", Jay Rosenblatt, the literature on postnatal depression in the mother and its effect on mother-infant interactions. We will cover clinical and pre-clinical findings highlighting putative neurobiological mechanisms underlying postpartum depression and how they relate to maternal behaviors and infant outcome. We also review animal models that investigate the neurobiology of maternal mood and disrupted maternal care. In particular, we discuss the implications of endogenous and exogenous manipulations of glucocorticoids on maternal care and mood. Lastly we discuss interventions during gestation and postpartum that may improve maternal symptoms and behavior and thus may alter developmental outcome of the offspring.