Effects of suckling on hypothalamic-pituitary-adrenal axis responses to psychosocial stress in postpartum lactating women

Autism, oxytocin and interoception

Autism is a pervasive developmental disorder characterized by profound social and verbal communication deficits, stereotypical motor behaviors, restricted interests, and cognitive abnormalities. Autism affects approximately 1% of children in developing countries. Given this prevalence, identifying risk factors and therapeutic interventions are pressing objectives—objectives that rest on neurobiologically grounded and psychologically informed theories about the underlying pathophysiology. In this article, we review the evidence that autism could result from a dysfunctional oxytocin system early in life. As a mediator of successful procreation, not only in the reproductive system, but also in the brain, oxytocin plays a crucial role in sculpting socio-sexual behavior. Formulated within a (Bayesian) predictive coding framework, we propose that oxytocin encodes the saliency or precision of interoceptive signals and enables the neuronal plasticity necessary for acquiring a generative model of the emotional and social 'self.' An aberrant oxytocin system in infancy could therefore help explain the marked deficits in language and social communication—as well as the sensory, autonomic, motor, behavioral, and cognitive abnormalities—seen in autism.

Neuroendocrinology of childbirth and mother-child attachment: the basis of an etiopathogenic model of perinatal neurobiological disorders

This review focuses on the neuroendocrine mechanisms in the mother and the newborn that are involved in the generation and consolidation of mother-child attachment. The role that different hormones and neurotransmitters play on the regulation of these mechanisms during parturition, the immediate postpartum period and lactation is discussed. Interferences in the initiation of mother-child attachment may have potential long-term effects for the behavior and affection of the newborn. Therefore, the possible consequences of alterations in the physiological neuroendocrine mechanisms of attachment, caused by elective Cesarean section, intrapartum hormonal manipulations, preterm delivery, mother-infant postpartum separation and bottle-feeding instead of breastfeeding are also discussed.

Emotion and mood adaptations in the peripartum female:complementary contributions of GABA and oxytocin

Peripartum hormones and sensory cues from young modify the maternal brain in ways that can render females either at risk for, or resilient to, elevated anxiety and depression. The neurochemical systems underlying these aspects of maternal emotional and mood states include the inhibitory neurotransmitter GABA and the neuropeptide oxytocin (OXT). Data from laboratory rodents indicate that increased activity at the GABA(A) receptor contributes to the postpartum suppression of anxiety-related behaviour that is mediated by physical contact with offspring, whereas dysregulation in GABAergic signalling results in deficits in maternal care, as well as anxiety- and depression-like behaviours during the postpartum period. Similarly, activation of the brain OXT system accompanied by increased OXT release within numerous brain sites in response to reproductive stimuli also reduces postpartum anxiety- and depression-like behaviours. Studies of peripartum women are consistent with these findings in rodents. Given the similar consequences of elevated central GABA and OXT activity on maternal anxiety and depression, balanced and partly reciprocal interactions between these two systems may be essential for their effects on maternal emotional and mood states, in addition to other aspects of postpartum behaviour and physiology.

Effect of lactation on maternal postpartum cardiac function and adiposity: a murine model

OBJECTIVE

Lactation is associated with reduction in maternal metabolic disease and hypertension later in life; however, findings in humans may be confounded by socioeconomic factors. We sought to determine the independent contribution of lactation on cardiovascular parameters and adiposity in a murine model.

STUDY DESIGN

Following delivery, CD-1 female mice were randomly divided into 2 groups: lactated (L; nursed pups for 3 weeks, n = 10), and nonlactated (NL; pups were removed after birth, n = 12). Blood pressure (BP) was assessed prepregnancy and at 1 and 2 months' postpartum. Visceral and subcutaneous adipose tissue determined by computed tomography and left ventricular ejection fraction, cardiac output, and the E/A ratio determined by microultrasound were evaluated at 1 and 2 months' postpartum. The results were analyzed using a Student t test (significance at P < .05).

RESULTS

We observed a significantly different maternal BP at 2 months' postpartum with relatively greater BP in NL (systolic BP: NL, 122.2 ± 7.2 vs L, 96.8 ± 9.8 mm Hg; P = .04; diastolic BP: NL, 87.0 ± 6.8 vs L, 65.9 ± 6.2 mm Hg; P = .04). Visceral adipose tissue was significantly increased in NL mice at 1 (22.0 ± 4.1% vs 10.7 ± 1.8%, P = .04) and 2 months' postpartum (22.9 ± 3.5% vs 11.2 ± 2.2%, P = .02), whereas subcutaneous adipose tissue did not differ between the groups. At 2 months' postpartum, ejection fraction (51.8 ± 1.5% vs 60.5 ± 3.8%; P = .04), cardiac output (14.2 ± 1.0 vs 18.0 ± 1.3 mL/min; P = .02) and mitral valve E/A ratio (1.38 ± 0.06 vs 1.82 ± 0.13; P = .04) were significantly lower in NL mice than L mice.

CONCLUSION

Our data provide evidence that interruption of lactation adversely affects postpartum maternal cardiovascular function and adiposity.

Using animal models to study post-partum psychiatric disorders

The post-partum period represents a time during which all maternal organisms undergo substantial plasticity in a wide variety of systems in order to ensure the well-being of the offspring. Although this time is generally associated with increased calmness and decreased stress responses, for a substantial subset of mothers, this period represents a time of particular risk for the onset of psychiatric disorders. Thus, post-partum anxiety, depression and, to a lesser extent, psychosis may develop, and not only affect the well-being of the mother but also place at risk the long-term health of the infant. Although the risk factors for these disorders, as well as normal peripartum-associated adaptations, are well known, the underlying aetiology of post-partum psychiatric disorders remains poorly understood. However, there have been a number of attempts to model these disorders in basic research, which aim to reveal their underlying mechanisms. In the following review, we first discuss known peripartum adaptations and then describe post-partum mood and anxiety disorders, including their risk factors, prevalence and symptoms. Thereafter, we discuss the animal models that have been designed in order to study them and what they have revealed about their aetiology to date. Overall, these studies show that it is feasible to study such complex disorders in animal models, but that more needs to be done in order to increase our knowledge of these severe and debilitating mood and anxiety disorders.

The maternal brain: an organ with peripartal plasticity

The time of pregnancy, birth, and lactation, is characterized by numerous specific alterations in several systems of the maternal body. Peripartum-associated changes in physiology and behavior, as well as their underlying molecular mechanisms, have been the focus of research since decades, but are still far from being entirely understood. Also, there is growing evidence that pregnancy and lactation are associated with a variety of alterations in neural plasticity, including adult neurogenesis, functional and structural synaptic plasticity, and dendritic remodeling in different brain regions. All of the mentioned changes are not only believed to be a prerequisite for the proper fetal and neonatal development, but moreover to be crucial for the physiological and mental health of the mother. The underlying mechanisms apparently need to be under tight control, since in cases of dysregulation, a certain percentage of women develop disorders like preeclampsia or postpartum mood and anxiety disorders during the course of pregnancy and lactation. This review describes common peripartum adaptations in physiology and behavior. Moreover, it concentrates on different forms of peripartum-associated plasticity including changes in neurogenesis and their possible underlying molecular mechanisms. Finally, consequences of malfunction in those systems are discussed.

Breastfeeding is negatively affected by prenatal depression and reduces postpartum depression

BACKGROUND

This prospective cohort study explored the effects of prenatal and postpartum depression on breastfeeding and the effect of breastfeeding on postpartum depression.

METHOD

The Edinburgh Postpartum Depression Scale (EPDS) was administered to 145 women at the first, second and third trimester, and at the neonatal period and 3 months postpartum. Self-report exclusive breastfeeding since birth was collected at birth and at 3, 6 and 12 months postpartum. Data analyses were performed using repeated-measures ANOVAs and logistic and multiple linear regressions.

RESULTS

Depression scores at the third trimester, but not at 3 months postpartum, were the best predictors of exclusive breastfeeding duration (β = -0.30, t = -2.08, p < 0.05). A significant decrease in depression scores was seen from childbirth to 3 months postpartum in women who maintained exclusive breastfeeding for ⩾3 months (F 1,65 = 3.73, p < 0.10, η p 2 = 0.05).

CONCLUSIONS

These findings suggest that screening for depression symptoms during pregnancy can help to identify women at risk for early cessation of exclusive breastfeeding, and that exclusive breastfeeding may help to reduce symptoms of depression from childbirth to 3 months postpartum.

Dose-dependent effects of chronic central infusion of oxytocin on anxiety, oxytocin receptor binding and stress-related parameters in mice

Chronic psychosocial stress is a recognized risk factor for various affective and somatic disorders. In an established murine model of chronic psychosocial stress, exposure to chronic subordinate colony housing (CSC) results in an alteration of physiological, behavioral, neuroendocrine and immunological parameters, including a long-lasting increase in anxiety, adrenal hypertrophy and thymus atrophy. Based on the stress-protective and anxiolytic properties of oxytocin (OXT) after acute administration in rodents and humans, the major aims of our study were to assess whether chronic administration of OXT dose-dependently affects the behavior and physiology of male mice, as for therapeutic use in humans, mostly chronic treatment approaches will be used. Further, we studied, whether chronic administration during CSC prevents stress-induced consequences. Our results indicate that chronic intracerebroventricular (ICV) infusion of OXT (15 days) at high (10ng/h), but not at low (1ng/h) dose, induces an anxiogenic phenotype with a concomitant reduction of OXT receptor (OXTR) binding within the septum, the basolateral and medial amygdala, as well as the median raphe nucleus. Further, we demonstrate that chronic ICV infusion of OXT (1ng/h) during a 19-day CSC exposure prevents the hyper-anxiety, thymus atrophy, adrenal hypertrophy, and decreased in vitro adrenal ACTH sensitivity. Thus, given both negative, but also beneficial effects seen after chronic OXT treatment, which appear to be dose-dependent, a deeper understanding of long-lasting treatment effects is required before OXT can be considered for long-term therapeutic use for the treatment of psychopathologies such as autism, schizophrenia or anxiety-disorders.

Oxytocin and vasopressin receptor polymorphisms interact with circulating neuropeptides to predict human emotional reactions to stress

Oxytocin (OT) and a polymorphism (rs53576) in the oxytocin receptor gene (OXTR) have been independently associated with stress reactivity, whereas oxytocin's sister peptide, arginine vasopressin (AVP) and polymorphisms in the vasopressin receptor gene (AVPR1A) have been independently associated with aggressive behavior. In this study, 68 men and 98 women were genotyped for the OXTR rs53576 polymorphism and the AVPR1A RS1 polymorphism. Baseline and poststressor levels of plasma OT, plasma AVP, positive affect, and anger were assessed. Women, but not men, with high levels of poststressor OT and the GG genotype of rs53576 felt the most positive affect after the stressor. Men, but not women, with high levels of poststressor AVP and the 320 allele of the RS1 polymorphism reported more poststressor anger than noncarriers. These data constitute the first evidence that oxytocin and vasopressin receptor genes interact with levels of OT and AVP to predict sex-specific emotional stress responses.

Maternal anxiety and breastfeeding: findings from the MAVAN (Maternal Adversity, Vulnerability and Neurodevelopment) Study

BACKGROUND

Maternal anxiety and depression may impair maternal intention, motivation, and self-efficacy in multiple domains associated with child health including breastfeeding.

OBJECTIVE

We tested the hypothesis that mothers who experience substantial anxiety during pregnancy or the postpartum period are at increased risk for reduced initiation, exclusivity, and continuation of breastfeeding.

METHODS

We obtained data on 255 Canadian pregnant women from the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) study recruited between June 2004 and February 2009. We utilized data collected from 18 to 23 weeks gestation through 12 months postpartum. Multivariate logistic regression was used to assess whether scores on the Hamilton Anxiety Scale (HAM-A) and State-Trait Anxiety Inventory (STAI) were associated with initiation, exclusivity, and continuation of breastfeeding.

RESULTS

Prenatal anxiety was not associated with breastfeeding outcomes. In adjusted models, a single point increase in HAM-A scores at 3 months postpartum was associated with an 11% reduction in the odds of exclusive breastfeeding at 6 months (adjusted odds ratio [aOR] = 0.89; 95% CI, 0.80-0.99). A single point increase in STAI State and STAI Trait scores at 3 months postpartum was associated with a 4% (aOR = 0.96; 95% CI, 0.92-0.99) and 7% (aOR = 0.93; 95% CI, 0.86-1.00) reduction, respectively, in the odds of any breastfeeding at 12 months.

CONCLUSION

Our findings suggest a relationship between maternal anxiety and reduced exclusivity and continuation of breastfeeding. Maternal anxiety should be actively monitored and managed appropriately in the postpartum period to support optimal breastfeeding practices.

Differential postpartum sensitivity to the anxiety-modulating effects of offspring contact is associated with innate anxiety and brainstem levels of dopamine beta-hydroxylase in female laboratory rats

In female mammals, the postpartum period involves dramatic shifts in many socioemotional behaviors. This includes a suppression of anxiety-related behaviors that requires recent physical contact with offspring. Factors contributing to differences among females in their susceptibility to the anxiety-modulating effect of offspring contact are unknown, but could include their innate anxiety and brain monoaminergic activity. Anxiety behavior was assessed in a large group of nulliparous female rats and the least-anxious and most-anxious tertiles were mated. Anxiety was assessed again postpartum after females were permitted or prevented from contacting their offspring 4 h before testing. Levels of dopamine β-hydroxylase (DBH, norepinephrine synthesizing enzyme) and tryptophan hydroxylase-2 (TPH2, serotonin synthesizing enzyme) were measured in the brainstem and dorsal raphe, respectively. It was found that anxiety-related behavior in the two groups did not differ when dams were permitted contact with offspring before testing. Removal of the offspring before testing, however, differentially affected anxiety based on dams' innate anxiety. Specifically, dams reverted back to their pre-mating levels of anxiety such that offspring removal slightly increased anxiety in the most-anxious females but greatly lowered anxiety in the least-anxious females. This reduction in anxiety in the least-anxious females after litter removal was associated with lower brainstem DBH. There was no relationship between females' anxiety and dorsal raphe TPH2. Thus, a primary effect of recent contact with offspring on anxiety-related behavior in postpartum rats is to shift females away from their innate anxiety to a more moderate level of responding. This effect is particularly true for females with the lowest anxiety, may be mediated by central noradrenergic systems, and has implications for their ability to attend to their offspring.

Oxytocin and Epstein-Barr virus: Stress biomarkers in the postpartum period among first-time mothers from São Paulo, Brazil

OBJECTIVES

The purpose of the study was to examine the relationship between self-reported stress levels among new mothers in São Paulo, Brazil and two biomarkers of stressful experience, oxytocin (OT) and Epstein-Barr Virus antibody level (EBV-ab), with planned pregnancy hypothesized as a moderator of biological response to stressful conditions.

METHODS

Sixty-three first-time mothers between the ages of 15 and 45 were recruited from neighborhoods in São Paulo, Brazil. Quantitative and qualitative data were collected longitudinally, bi-weekly between two and 12 weeks postpartum. OT level was assessed from breast milk samples and EBV-ab from blood spot samples. An Interpersonal Satisfaction scale was developed, validated, and administered, along with the Cohen perceived stress scale (PSS).

RESULTS

In-depth interview data revealed unplanned pregnancy to be a significant stressor in the lives of first-time mothers. In linear regression, OT level was negatively associated with interpersonal satisfaction score (P = 0.022) and positively associated with PSS score (P = 0.007). When splitting the sample by planned status of the pregnancy, women with an unplanned pregnancy showed a strengthened positive association between OT level and PSS (P = 0.001; Adj R(2) = 0.44) and negative association with interpersonal satisfaction (P = 0.017; Adj R(2) = 0.15), while no associations existed for women with a planned pregnancy. EBV-ab level was not correlated or associated with stress/satisfaction measures.

CONCLUSION

OT is an effective biomarker in the measurement of stress in the body, and additionally reflects differential experiences with difficult interpersonal circumstances, such as unplanned pregnancy. By contrast, EBV-ab failed to reflect differences in self-reported stress levels between mothers.

Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test

Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.

Oxytocin and postpartum depression: delivering on what's known and what's not

The role of oxytocin in the treatment of postpartum depression has been a topic of growing interest. This subject carries important implications, given that postpartum depression can have detrimental effects on both the mother and her infant, with lifelong consequences for infant socioemotional and cognitive development. In recent years, oxytocin has received attention for its potential role in many neuropsychiatric conditions beyond its well-described functions in childbirth and lactation. In the present review, we present available data on the clinical characteristics and neuroendocrine foundations of postpartum depression. We outline current treatment modalities and their limitations, and proceed to evaluate the potential role of oxytocin in the treatment of postpartum depression. The aim of the present review is twofold: (a) to bring together evidence from animal and human research concerning the role of oxytocin in postpartum depression, and (b) to highlight areas that deserve further research in order to bring a fuller understanding of oxytocin's therapeutic potential. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Intranasal oxytocin effects on social cognition: a critique

The last decade has seen a large number of published findings supporting the hypothesis that intranasally delivered oxytocin (OT) can enhance the processing of social stimuli and regulate social emotion-related behaviors such as trust, memory, fidelity, and anxiety. The use of nasal spray for administering OT in behavioral research has become a standard method, but many questions still exist regarding its action. OT is a peptide that cannot cross the blood-brain barrier, and it has yet to be shown that it does indeed reach the brain when delivered intranasally. Given the evidence, it seems highly likely that OT does affect behavior when delivered as a nasal spray. These effects may be driven by at least three possible mechanisms. First, the intranasally delivered OT may diffuse directly into the CNS where it directly engages OT receptors. Second, the intranasally delivered OT may trigger increased central release via an indirect peripheral mechanism. And third, the indirect peripheral effects may directly lead to behavioral effects via some mechanism other than increased central release. Although intranasally delivered OT likely affects behavior, there are conflicting reports as to the exact nature of those behavioral changes: some studies suggest that OT effects are not always "pro-social" and others suggest effects on social behaviors are due to a more general anxiolytic effect. In this critique, we draw from work in healthy human populations and the animal literature to review the mechanistic aspects of intranasal OT delivery, and to discuss intranasal OT effects on social cognition and behavior. We conclude that future work should control carefully for anxiolytic and gender effects, which could underlie inconsistencies in the existing literature. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Reading the mind in the infant eyes: paradoxical effects of oxytocin on neural activity and emotion recognition in watching pictures of infant faces

The neuropeptide oxytocin facilitates parental caregiving and is involved in the processing of infant vocal cues. In this randomized-controlled trial with functional magnetic resonance imaging we examined the influence of intranasally administered oxytocin on neural activity during emotion recognition in infant faces. Blood oxygenation level dependent (BOLD) responses during emotion recognition were measured in 50 women who were administered 16 IU of oxytocin or a placebo. Participants performed an adapted version of the Infant Facial Expressions of Emotions from Looking at Pictures (IFEEL pictures), a task that has been developed to assess the perception and interpretation of infants' facial expressions. Experimentally induced oxytocin levels increased activation in the inferior frontal gyrus (IFG), the middle temporal gyrus (MTG) and the superior temporal gyrus (STG). However, oxytocin decreased performance on the IFEEL picture task. Our findings suggest that oxytocin enhances processing of facial cues of the emotional state of infants on a neural level, but at the same time it may decrease the correct interpretation of infants' facial expressions on a behavior level. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Oxytocin reduces reward-driven food intake in humans

Experiments in animals suggest that the neuropeptide oxytocin acts as an anorexigenic signal in the central nervous control of food intake. In humans, however, research has almost exclusively focused on the involvement of oxytocin in the regulation of social behavior. We investigated the effect of intranasal oxytocin on ingestion and metabolic function in healthy men. Food intake in the fasted state was examined 45 min after neuropeptide administration, followed by the assessment of olfaction and reward-driven snack intake in the absence of hunger. Energy expenditure was registered by indirect calorimetry, and blood was repeatedly sampled to determine concentrations of blood glucose and hormones. Oxytocin markedly reduced snack consumption, restraining, in particular, the intake of chocolate cookies by 25%. Oxytocin, moreover, attenuated basal and postprandial levels of adrenocorticotropic hormone and cortisol and curbed the meal-related rise in plasma glucose. Energy expenditure and hunger-driven food intake as well as olfactory function were not affected. Our results indicate that oxytocin, beyond its role in social bonding, regulates nonhomeostatic, reward-related energy intake, hypothalamic-pituitary-adrenal axis activity, and the glucoregulatory response to food intake in humans. These effects can be assumed to converge with the psychosocial function of oxytocin and imply possible applications in the treatment of metabolic disorders.

Does intranasal oxytocin promote prosocial behavior to an excluded fellow player? A randomized-controlled trial with Cyberball

The neuropeptide oxytocin has been shown to stimulate prosocial behavior. However, recent studies indicate that adverse early caregiving experiences may moderate the positive effects of oxytocin. In this double blind randomized-controlled trial we investigated the effects of oxytocin on prosocial behavior during a virtual ball-tossing game called Cyberball. We examined the influence of oxytocin on prosocial helping behavior toward a socially excluded person who was known to the participant, taking into account early caregiving experiences and the emotional facial expression of the excluded person as potential moderators. Participants were 54 women who received a nasal spray containing either 16IU of oxytocin or a placebo and had reported how often their mother used love withdrawal as a disciplinary strategy involving withholding love and affection after a failure or misbehavior. We found that participants compensated for other players' ostracism by throwing the ball more often toward the excluded player. Oxytocin administration further increased the number of ball throws toward the excluded person, but only in individuals who experienced low levels of maternal love withdrawal. The facial expression of the excluded person did not affect prosocial helping behavior and did not moderate the effects of oxytocin. Our findings indicate that the positive effects of oxytocin on prosocial behavior toward a victim of social exclusion are limited to individuals with supportive family backgrounds.

Breastfeeding and postpartum depression: state of the art review

OBJECTIVE

To review the literature on the association between breastfeeding and postpartum depression.

SOURCES

A review of literature found on MEDLINE/PubMed database.

SUMMARY OF FINDINGS

The literature consistently shows that breastfeeding provides a wide range of benefits for both the child and the mother. The psychological benefits for the mother are still in need of further research. Some studies point out that pregnancy depression is one of the factors that may contribute to breastfeeding failure. Others studies also suggest an association between breastfeeding and postpartum depression; the direction of this association is still unclear. Breastfeeding can promote hormonal processes that protect mothers against postpartum depression by attenuating cortisol response to stress. It can also reduce the risk of postpartum depression, by helping the regulation of sleep and wake patterns for mother and child, improving mother's self-efficacy and her emotional involvement with the child, reducing the child's temperamental difficulties, and promoting a better interaction between mother and child.

CONCLUSIONS

Studies demonstrate that breastfeeding can protect mothers from postpartum depression, and are starting to clarify which biological and psychological processes may explain this protection. However, there are still equivocal results in the literature that may be explained by the methodological limitations presented by some studies.

Men perform comparably to women in a perspective taking task after administration of intranasal oxytocin but not after placebo

Oxytocin (OT) is thought to play an important role in human interpersonal information processing and behavior. By inference, OT should facilitate empathic responding, i.e., the ability to feel for others and to take their perspective. In two independent double-blind, placebo-controlled between-subjects studies, we assessed the effect of intranasally administered OT on affective empathy and perspective taking, whilst also examining potential sex differences (e.g., women being more empathic than men). In study 1, we provided 96 participants (48 men) with an empathy scenario and recorded self-reports of empathic reactions to the scenario, while in study 2, a sample of 120 individuals (60 men) performed a computerized implicit perspective taking task. Whilst results from Study 1 showed no influence of OT on affective empathy, we found in Study 2 that OT exerted an effect on perspective taking ability in men. More specifically, men responded faster than women in the placebo group but they responded as slowly as women in the OT group. We conjecture that men in the OT group adopted a social perspective taking strategy, such as did women in both groups, but not men in the placebo group. On the basis of results across both studies, we suggest that self-report measures (such as used in Study 1) might be less sensitive to OT effects than more implicit measures of empathy such as that used in Study 2. If these assumptions are confirmed, one could infer that OT effects on empathic responses are more pronounced in men than women, and that any such effect is best studied using more implicit measures of empathy rather than explicit self-report measures.

Biological aspects of postpartum depression

In comparison with the vast epidemiological literature on postpartum depression (PPD), relatively few studies have examined the biological aspects of the disorder. However, research into the biological mechanisms of PPD is a challenging task, as normal pregnancy and the postpartum period cause adaptive endocrine changes, which would otherwise be considered pathological in nonpregnant women. This review focuses on the adaptive changes of childbearing and nursing, which ultimately may put women at increased risk of PPD. In light of the normal physiology, the authors also attempt to describe the current evidence of the biological changes associated with the development of depression in the postpartum period, including ovarian steroids, the hypothalamic-pituitary-adrenal axis, the serotonergic neurotransmitter system, the thyroid system and inflammatory markers. In addition, current knowledge on candidate genes associated with PPD is reviewed.

Sniffing around oxytocin: review and meta-analyses of trials in healthy and clinical groups with implications for pharmacotherapy

The popularity of oxytocin (OT) has grown exponentially during the past decade, and so has the number of OT trials in healthy and clinical groups. We take stock of the evidence from these studies to explore potentials and limitations of pharmacotherapeutic applications. In healthy participants, intranasally administered OT leads to better emotion recognition and more trust in conspecifics, but the effects appear to be moderated by context (perceived threat of the 'out-group'), personality and childhood experiences. In individuals with untoward childhood experiences, positive behavioral or neurobiological effects seem lowered or absent. In 19 clinical trials, covering autism, social anxiety, postnatal depression, obsessive-compulsive problems, schizophrenia, borderline personality disorder and post-traumatic stress, the effects of OT administration were tested, with doses ranging from 15 IU to more than 7000 IU. The combined effect size was d=0.32 (N=304; 95% confidence interval (CI): 0.18-0.47; P<0.01). However, of all disorders, only studies on autism spectrum disorder showed a significant combined effect size (d=0.57; N=68; 95% CI: 0.15-0.99; P<0.01). We hypothesize that for some of the other disorders, etiological factors rooted in negative childhood experiences may also have a role in the diminished effectiveness of treatment with OT.

Psychobiological mechanisms underlying the social buffering of the hypothalamic-pituitary-adrenocortical axis: a review of animal models and human studies across development

Discovering the stress-buffering effects of social relationships has been one of the major findings in psychobiology in the last century. However, an understanding of the underlying neurobiological and psychological mechanisms of this buffering is only beginning to emerge. An important avenue of this research concerns the neurocircuitry that can regulate the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis. The present review is a translational effort aimed at integrating animal models and human studies of the social regulation of the HPA axis from infancy to adulthood, specifically focusing on the process that has been named social buffering. This process has been noted across species and consists of a dampened HPA axis stress response to threat or challenge that occurs with the presence or assistance of a conspecific. We describe aspects of the relevant underlying neurobiology when enough information exists and expose major gaps in our understanding across all domains of the literatures we aimed to integrate. We provide a working conceptual model focused on the role of oxytocinergic systems and prefrontal neural networks as 2 of the putative biological mediators of this process, and propose that the role of early experiences is critical in shaping later social buffering effects. This synthesis points to both general future directions and specific experiments that need to be conducted to build a more comprehensive model of the HPA social buffering effect across the life span that incorporates multiple levels of analysis: neuroendocrine, behavioral, and social.

Depression, sleep quality, and maternal well-being in postpartum women with a history of sexual assault: a comparison of breastfeeding, mixed-feeding, and formula-feeding mothers

BACKGROUND

Women with a history of sexual assault are at increased risk for sleep difficulties and depression in their first year of motherhood. Breastfeeding improves sleep parameters and lowers risk of depression for women in general. However, it is unknown whether breastfeeding is related to maternal depression, sleep quality, and maternal well-being in sexual assault survivors. We examined the association between sexual assault and several indices of sleep, depression, and maternal well-being in a large sample of sexual assault survivors in the first year postpartum. We also explored whether feeding method was related to our outcome variables for both sexually assaulted and non-assaulted women.

SUBJECTS AND METHODS

A sample of 6,410 mothers of infants 0-12 months old participated in the online Survey of Mothers' Sleep and Fatigue; 994 women had a history of sexual assault.

RESULTS

As predicted, women with a history of sexual assault had a number of sleep difficulties, increased risk of depression, and overall poorer subjective well-being than their non-assaulted counterparts. However, sexual assault survivors who were breastfeeding were at lower risk on all of the sleep and depression parameters than sexual assault survivors who were mixed or formula feeding.

CONCLUSIONS

Sexual assault has a pervasive negative effect on new mothers' sleep quality and risk of depression. However, these negative effects were less severe for the breastfeeding mothers than they were for the mixed- or formula-feeding mothers.

Adaptive changes in basal and stress-induced HPA activity in lactating and post-lactating female rats

Lactation represents a period of marked adaptation of the hypothalamo-pituitary-adrenal HPA axis. We characterized basal and stress-induced HPA activity during lactation and experimental weaning using dynamic blood sampling in rats. Pulsatile and diurnal corticosterone release occurred at all reproductive stages studied (virgin; day 10 of lactation; 3 and 14 days after experimental weaning on day 10 of lactation). However, in lactating rats the diurnal peak was significantly reduced, resulting in a flattened rhythm, and three days after weaning, basal HPA activity was markedly suppressed: the number of pulses and underlying basal levels of corticosterone were reduced and the diurnal rise phase delayed. Marked changes in the HPA response to 10 min noise stress also occurred at these times: being completely absent in lactating animals, but restored and highly prolonged in early weaned animals. Injection of methylprednisolone (2 mg, iv) was used to determine whether changes in fast glucocorticoid suppression correlated with these adaptive changes. Methylprednisolone induced a rapid suppression of corticosterone in virgin animals, but this effect was markedly attenuated in lactating and early weaned animals and was accompanied by significant changes in relative expression of hippocampal glucocorticoid and mineralocorticoid receptor mRNA. All effects were reversed or partially reversed 14 days after experimental weaning. Thus, the presence of the pups has an important influence on regulation of the HPA axis, and while postpartum adaptations are reversible, acute weaning evokes marked reorganisation of basal and stress-induced HPA activity.

Lower sexual interest in postpartum women: relationship to amygdala activation and intranasal oxytocin

During the postpartum period, women experience significant changes in their neuroendocrine profiles and social behavior compared to before pregnancy. A common experience with motherhood is a decrease in sexual desire. Although the lifestyle and peripheral physiological changes associated with parturition might decrease a woman's sexual interest, we hypothesized that there are also hormone-mediated changes in women's neural response to sexual and infant stimuli with altered reproductive priorities. We predicted that amygdala activation to sexually arousing stimuli would be suppressed in postpartum versus nulliparous women, and altered with intranasal oxytocin administration. To test this, we measured amygdala activation using fMRI in response to sexually arousing pictures, infant pictures, and neutral pictures in 29 postpartum and 30 nulliparous women. Half of the women received a dose of exogenous oxytocin before scanning. As predicted, nulliparous women subjectively rated sexual pictures to be more arousing, and infant pictures to be less arousing, than did postpartum women. However, nulliparous women receiving the nasal oxytocin spray rated the infant photos as arousing as did postpartum women. Right amygdala activation was lower in postpartum versus nulliparous women in response to sexual, infant, and neutral images, suggesting a generalized decrease in right amygdala responsiveness to arousing images with parturition. There was no difference in right amygdala activation with nasal spray application. Postpartum women therefore appear to experience a decrease in sexual interest possibly as a feature of a more generalized decrease in amygdala responsiveness to arousing stimuli.

Balance of brain oxytocin and vasopressin: implications for anxiety, depression, and social behaviors

Oxytocin and vasopressin are regulators of anxiety, stress-coping, and sociality. They are released within hypothalamic and limbic areas from dendrites, axons, and perikarya independently of, or coordinated with, secretion from neurohypophysial terminals. Central oxytocin exerts anxiolytic and antidepressive effects, whereas vasopressin tends to show anxiogenic and depressive actions. Evidence from pharmacological and genetic association studies confirms their involvement in individual variation of emotional traits extending to psychopathology. Based on their opposing effects on emotional behaviors, we propose that a balanced activity of both brain neuropeptide systems is important for appropriate emotional behaviors. Shifting the balance between the neuropeptide systems towards oxytocin, by positive social stimuli and/or psychopharmacotherapy, may help to improve emotional behaviors and reinstate mental health.

Amygdala response to negative images in postpartum vs nulliparous women and intranasal oxytocin

The neuroendocrine state of new mothers may alter their neural processing of stressors in the environment through modulatory actions of oxytocin on the limbic system. We predicted that amygdala sensitivity to negatively arousing stimuli would be suppressed in postpartum compared to nulliparous women and that this suppression would be modulated by administration of oxytocin nasal spray. We measured brain activation (fMRI) and subjective arousal in response to negatively arousing pictures in 29 postpartum and 30 nulliparous women who received either oxytocin nasal spray or placebo before scanning. Pre- and post-exposure urinary cortisol levels were also measured. Postpartum women (placebo) demonstrated lower right amygdala activation in response to negative images, lower cortisol and lower negative photo arousal ratings to nulliparous women. Nulliparous women receiving oxytocin had lower right amygdala activation compared to placebo. Cortisol levels in the placebo group, and ratings of arousal across all women, were positively associated with right amygdala activation. Together, these findings demonstrate reductions in both amygdala activation and subjective negative arousal in untreated postpartum vs nulliparous women, supporting the hypothesis of an attenuated neural response to arousing stimuli in postpartum women. A causal role of oxytocin and the timing of potential effects require future investigation.

No laughing matter: intranasal oxytocin administration changes functional brain connectivity during exposure to infant laughter

Infant laughter is a rewarding experience. It activates neural reward circuits and promotes parental proximity and care, thus facilitating parent-infant attachment. The neuropeptide oxytocin might enhance the incentive salience of infant laughter by modulating neural circuits related to the perception of infant cues. In a randomized controlled trial with functional magnetic resonance imaging we investigated the influence of intranasally administered oxytocin on functional brain connectivity in response to infant laughter. Blood oxygenation level-dependent responses to infant laughter were measured in 22 nulliparous women who were administered oxytocin and 20 nulliparous women who were administered a placebo. Elevated oxytocin levels reduced activation in the amygdala during infant laughter and enhanced functional connectivity between the amygdala and the orbitofrontal cortex, the anterior cingulate, the hippocampus, the precuneus, the supramarginal gyri, and the middle temporal gyrus. Increased functional connectivity between the amygdala and regions involved in emotion regulation may reduce negative emotional arousal while enhancing the incentive salience of the infant laughter.

The contributions of oxytocin and vasopressin pathway genes to human behavior

Arginine vasopressin (AVP) and oxytocin (OXT) are social hormones and mediate affiliative behaviors in mammals and as recently demonstrated, also in humans. There is intense interest in how these simple nonapeptides mediate normal and abnormal behavior, especially regarding disorders of the social brain such as autism that are characterized by deficits in social communication and social skills. The current review examines in detail the behavioral genetics of the first level of human AVP-OXT pathway genes including arginine vasopressin 1a receptor (AVPR1a), oxytocin receptor (OXTR), AVP (AVP-neurophysin II [NPII]) and OXT (OXT neurophysin I [NPI]), oxytocinase/vasopressinase (LNPEP), ADP-ribosyl cyclase (CD38) and arginine vasopressin 1b receptor (AVPR1b). Wherever possible we discuss evidence from a variety of research tracks including molecular genetics, imaging genomics, pharmacology and endocrinology that support the conclusions drawn from association studies of social phenotypes and detail how common polymorphisms in AVP-OXT pathway genes contribute to the behavioral hard wiring that enables individual Homo sapiens to interact successfully with conspecifics. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Duration of lactation and incidence of maternal hypertension: a longitudinal cohort study

Never or curtailed lactation has been associated with an increased risk for incident hypertension, but the effect of exclusive breastfeeding is unknown. The authors conducted an observational cohort study of 55,636 parous women in the US Nurses' Health Study II. From 1991 to 2005, participants reported 8,861 cases of incident hypertension during 660,880 person-years of follow-up. Never or curtailed lactation was associated with an increased risk of incident hypertension. Compared with women who breastfed their first child for ≥12 months, women who did not breastfeed were more likely to develop hypertension (hazard ratio (HR) = 1.27, 95% confidence interval (CI): 1.18, 1.36), adjusting for family history and lifestyle covariates. Women who never breastfed were more likely to develop hypertension than women who exclusively breastfed their first child for ≥6 months (HR = 1.29, 95% CI: 1.20, 1.40). The authors found similar results for women who had never breastfed compared with those who had breastfed each child for an average of ≥12 months (HR = 1.22, 95% CI: 1.13, 1.32). In conclusion, never or curtailed lactation was associated with an increased risk of incident maternal hypertension, compared with the recommended ≥6 months of exclusive or ≥12 months of total lactation per child, in a large cohort of parous women.

Short-term changes in fathers' hormones during father-child play: impacts of paternal attitudes and experience

Hormonal differences between fathers and non-fathers may reflect an effect of paternal care on hormones. However, few studies have evaluated the hormonal responses of fathers after interacting with their offspring. Here we report results of a 30-minute in-home experiment in which Filipino fathers played with their toddlers and consider whether paternal experience and men's perceptions of themselves as fathers affect hormonal changes. Fathers provided saliva and dried blood spot samples at baseline (B) and 30 (P30) and 60 (P60, saliva only) minutes after the interaction. We tested whether testosterone (T), cortisol (CORT), and prolactin (PRL) shifted after the intervention. In the total sample, T did not vary over the study period, while CORT declined from B to P30 and P60, and PRL also declined from B to P30. Fathers who spent more time in daily caregiving and men who thought their spouses evaluated them positively as parental caregivers experienced a larger decline in PRL (B to P30) compared to other fathers. First-time fathers also had larger declines in PRL compared to experienced fathers. Experienced fathers also showed a greater decline in CORT (B to P60) compared to first-time fathers. These results suggest that males' paternal experience and age of offspring affect hormonal responses to father-child play and that there is a psychobiological connection between men's perceptions of themselves as fathers and their hormonal responsivity to childcare.

Oxytocin decreases handgrip force in reaction to infant crying in females without harsh parenting experiences

Infant crying can elicit sensitive caregiving as well as hostility and harsh parenting responses. In the current study (N = 42 females) with a double-blind experimental design, we tested the effect of intranasal oxytocin administration on the use of excessive force using a hand-grip dynamometer during listening to infant cry sounds. Participants' experiences with harsh parental discipline during childhood were found to moderate the effect of oxytocin administration on the use of excessive force. Participants' whose parents did not discipline them harshly used less excessive force in the oxytocin condition, but for participants who were disciplined harshly there was no difference between the oxytocin and placebo condition. Such effects were not found during listening to infant laughter. We conclude that early caregiving experiences constitute an important moderator of the prosocial and/or stress-reducing effects of oxytocin. Oxytocin administration may increase trust and cooperation in individuals with supportive backgrounds, but not generate this effect in individuals who as a consequence of unfavorable early caregiving experiences may have a bias toward negative interpretation of social cues.

Exposure to chronic pregnancy stress reverses peripartum-associated adaptations: implications for postpartum anxiety and mood disorders

Maternal adaptations, such as decreased anxiety and attenuated stress responsiveness, are necessary to enable successful postnatal development of the offspring. However, there is growing evidence that they are also required to protect the mental health of the mother and that exposure to chronic stress during pregnancy may prevent such adaptations. Overcrowding stress (24 h) and restraint stress (2 × 1 h) were employed on alternate days between pregnancy d 4-16 to examine the impact of chronic pregnancy stress on relevant behavioral, neuroendocrine, and neuronal peripartum adaptations. To determine whether the chronic stress-induced alterations were specific to the peripartum period, we included virgins as controls. Validating the stress procedure, we demonstrated decreased body-weight gain and increased adrenal weight in stressed dams, relative to their nonstressed controls. Chronic stress prevented a number of peripartum adaptations, including basal plasma hypercorticosterone levels, increased oxytocin mRNA expression in the hypothalamic paraventricular nucleus, and anxiolysis. However, chronic stress did not prevent the peripartum-associated decrease in CRH mRNA expression or attenuate corticosterone response to an acute stressor, nor did it affect hypothalamic vasopressin mRNA expression. Illustrating the specificity of these stress-induced changes to the peripartum period, none of these parameters were affected in stressed virgins. Although chronic stress did not alter depression-related behavior, it reversed the response to acute imipramine treatment and increased active maternal behavior in lactation. Thus, prevention of the peripartum-associated increases in basal corticosterone and oxytocin system activity by pregnancy stress reveal two alterations that may increase the risk of postpartum psychiatric disorders, particularly anxiety.

Hormonal and behavioral responses to stress in lactating and non-lactating female common marmosets (Callithrix jacchus)

In several mammalian species, hypothalamic-pituitary-adrenal (HPA) and behavioral responses to stressors are down-regulated in lactating females, possibly preventing stress-induced disruptions of maternal care. Experimental elevations of HPA axis hormones have been found to inhibit maternal behavior in lactating common marmoset monkeys (Callithrix jacchus), raising the question of whether lactating female marmosets also have blunted endogenous responses to stress. Therefore, we compared HPA and behavioral responses to standardized stressors in reproductively experienced female common marmosets that were undergoing ovulatory cycles and that either were (N=7) or were not lactating (N=8). Each marmoset underwent (1) a restraint stressor during the early follicular phase of the ovarian cycle (approximately 5 weeks postpartum for lactating females) and (2) exposure to a simulated hawk predator during the early to mid-luteal phase (approximately 7 weeks postpartum for lactating females). Lactating females were tested in the presence of one of their infants. Blood samples were collected before, during, and immediately after each test for determination of plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations. Both stressors caused significant elevations in plasma ACTH and cortisol levels, and significant decreases in cortisol:ACTH ratios; however, lactating and non-lactating females showed no significant differences in their endocrine or behavioral responses to either stressor, or in baseline ACTH or cortisol levels. These findings suggest that in contrast to several other mammalian species, lactating female marmosets maintain full behavioral and HPA responsiveness to stress, at least in the presence of their infants.

Oxytocin and vasopressin in the human brain: social neuropeptides for translational medicine

The neuropeptides oxytocin (OXT) and arginine vasopressin (AVP) are evolutionarily highly conserved mediators in the regulation of complex social cognition and behaviour. Recent studies have investigated the effects of OXT and AVP on human social interaction, the genetic mechanisms of inter-individual variation in social neuropeptide signalling and the actions of OXT and AVP in the human brain as revealed by neuroimaging. These data have advanced our understanding of the mechanisms by which these neuropeptides contribute to human social behaviour. OXT and AVP are emerging as targets for novel treatment approaches--particularly in synergistic combination with psychotherapy--for mental disorders characterized by social dysfunction, such as autism, social anxiety disorder, borderline personality disorder and schizophrenia.

Direct breast-feeding in the neonatal intensive care unit: is it important?

OBJECTIVE

Rates of breast milk feeding at hospital discharge are low in premature infants due to the many associated challenges. Although there are many benefits associated with breast milk, the effects of direct breast-feeding in the neonatal intensive care unit (NICU) have not been identified. The purpose of this study was to investigate the relationship between direct breast-feeding (infant sucking directly from the breast) and duration and success with breast milk feedings until discharge in premature infants.

STUDY DESIGN

This retrospective cohort was conducted on 66 very-low birth weight infants whose mothers initiated breast milk feedings in the NICU. Chart review revealed documented type (breast milk with or without fortifiers or type of infant formula), volume and mode (nasogastric tube, breast or bottle) of all gastric feeds for each day of NICU hospitalization. From this documentation, whether the mother initiated breast milk feedings, the number of times the mother put the infant to breast, the gestational age of the first direct breast-feeding, whether the first oral feeding was at the breast, the duration of breast milk feedings and whether breast milk feedings continued until NICU discharge were determined. Associations between breast-feeding participatory factors and breast milk feeding outcomes were investigated using linear and logistic regression.

RESULT

Positive associations were found between breast milk feedings at discharge and mothers putting their infants directly to breast in the NICU (P=0.0005). The duration of breast milk feedings was associated with: mothers putting their infants directly to breast (P=0.0110), whether the first oral sucking feeding was at the breast (P=0.0108) and the gestational age of the first breast-feeding attempt (P<0.0001).

CONCLUSION

Breast milk feedings are encouraged in most NICU's, but direct breast-feeding is often overlooked as an important area of research in the tightly controlled environment of the NICU. This study demonstrates a link between direct breast-feeding behaviors in the NICU and success with provision of milk at discharge, as well as how early participation can be an important factor in the breast-feeding process for mothers of NICU infants. More research on the effects of direct breast-feeding is warranted.

Urinary oxytocin as a noninvasive biomarker of positive emotion in dogs

A reliable assay based on physiological parameters that does not require subjective input from the owners is required to assess positive emotions in dogs. In addition, when viewed from an animal welfare perspective, physiological parameters should be collected in a noninvasive manner. Oxytocin (OT) is a biomarker that may be associated with a calm, relaxed state, and positive emotion. We measured the time-lapse in the concentration of plasma OT relative to urinary OT using a radioimmunoassay with sufficient sensitivity and low variability, and examined the relationship between OT and cortisol. Six dogs were injected with exogenous OT intravenously to increase the blood OT concentration. As a result, the highest concentration of urinary OT occurred 1h after the injection, although there was little change in urinary cortisol. Moreover, to evaluate the influence of stimuli on urinary OT and cortisol, we provided three stimuli of eating food, exercising and stroking, all of which were assumed to inspire a positive emotion in dogs, and significantly increased urinary OT concentrations. Our findings indicate that urinary OT might be useful as a noninvasive and objective biomarker of positive emotion in dogs.

Oxytocin modulates amygdala, insula, and inferior frontal gyrus responses to infant crying: a randomized controlled trial

BACKGROUND

Oxytocin facilitates parental caregiving and mother-infant bonding and might be involved in responses to infant crying. Infant crying provides information about the physical status and mood of the infant and elicits parental proximity and caregiving. Oxytocin might modulate the activation of brain structures involved in the perception of cry sounds-specifically the insula, the amygdala, and the thalamocingulate circuit-and thereby affect responsiveness to infant crying.

METHOD

In a randomized controlled trial we investigated the influence of intranasally administered oxytocin on neural responses to infant crying with functional magnetic resonance imaging. Blood oxygenation level-dependent responses to infant crying were measured in 21 women who were administered oxytocin and 21 women who were administered a placebo.

RESULTS

Induced oxytocin levels reduced, experimentally, activation in the amygdala and increased activation in the insula and inferior frontal gyrus pars triangularis.

CONCLUSIONS

Our findings suggest that oxytocin promotes responsiveness to infant crying by reducing activation in the neural circuitry for anxiety and aversion and increasing activation in regions involved in empathy.

Maternal absence of the parathyroid hormone 2 receptor affects postnatal pup development

During the lactation period, mothers have a variety of adaptive changes in brain physiology and behaviour that allow them to properly raise their pups. The exact circuitries and mechanisms responsible for these changes are not fully understood. Recent evidence suggests that the neuropeptide tuberoinfundibular peptide of 39 residues (TIP39) and its receptor, the parathyroid hormone 2 receptor (PTH2-R), contribute to these mechanisms. To further investigate this idea, we evaluated the growth rate of pups from dams with a genetically inactivated PTH2-R (PTH2-R-KO), as well as maternal behavioural and neuroendocrine parameters. We observed that PTH2-R-KO-reared pups had a slowed growth rate. This was associated with a reduced volume of milk yielded by PTH2-R-KO dams after 30-min suckling compared to wild-type (WT) dams when pups were returned after 5 h of separation. Our data suggest a reduced sensitivity of PTH2-R-KO dams to pup stimulation. We also observed a significant reduction in suckling-induced c-Fos expression in the paraventricular hypothalamic nucleus and signs of lower prolactin levels in the PTH2-R-KO dams. Our data suggest that the reduced growth rate of PTH2-R-KO-reared pups was likely the result of alterations in the milk-production pathway rather than modifications in behaviour. Although PTH2-R-KO dams showed increased anxiety in the elevated zero-maze test, no differences from WT dams in maternal behaviour were observed. Taken together, our findings suggest the involvement of the TIP39/PTH2-R system in the pathways involved in the successful development of the pups.

The Trier Social Stress Test for Groups (TSST-G): A new research tool for controlled simultaneous social stress exposure in a group format

Psychological stress is an ubiquitous challenge across human cultures affecting mental and physical health. Recent evidence indicates that performance tasks combining elements of socio-evaluative threat and uncontrollability elicit reliable stress responses. The Trier Social Stress Test (TSST) is the most frequently used psychological protocol in stress research; however, to date it has only been available in a single-subject version. In particular, there is an increasing need in several emerging research fields such as stress research or social neurosciences for a standardized research tool to expose relatively large groups of subjects to controlled simultaneous stress. In search of a laboratory stressor that allows simultaneous stress exposure in a group format, we exposed a total of 25 healthy male participants to the Trier Social Stress Test for Groups (TSST-G; public speaking and mental arithmetic tasks in front of a panel of two evaluators in groups of six participants) and a specific control condition. Results showed that the TSST-G induced significant increases in cortisol, heart rate, and psychological stress responses. The TSST-G provides a novel, effective, and economical protocol for experimental paradigms requiring simultaneous stress induction in multiple participants.

Plasma oxytocin is related to lower cardiovascular and sympathetic reactivity to stress

In addition to known reproductive and social affiliation functions, oxytocin (OT) has been identified as a cardiovascular hormone. OT synthesis and receptors are found in cardiac and vascular tissue. Animal studies suggest that OT activates an 'anti-stress' response that reduces cardiovascular and neuroendocrine stress reactivity. We tested 28 early postpartum mothers, obtaining multiple blood samples for OT, the sympathetic marker, norepinephrine (NE), and the lactation hormone, prolactin, while monitoring their cardiovascular responses to two stressors: public speaking and forehead cold pressor. Although plasma OT did not increase reliably from pre-stress levels during stressors, greater overall OT level was related to greater vasodilation and cardiac stroke volume responses to both tasks, to reduction in heart rate to the cold pressor, as well as to lower plasma NE and higher prolactin levels. In contrast, higher NE was linked to increases in heart rate and decreases in stroke volume. These data support a cardioprotective role for OT, which may influence the magnitude and hemodynamic determinants of cardiovascular stress responses.

Duration of lactation and maternal adipokines at 3 years postpartum

OBJECTIVE

Lactation has been associated with reduced maternal risk of type 2 diabetes, the metabolic syndrome, and cardiovascular disease. We examined the relationship between breastfeeding duration and maternal adipokines at 3 years postpartum.

RESEARCH DESIGN AND METHODS

We used linear regression to relate the duration of lactation to maternal leptin, adiponectin, ghrelin, and peptide YY (PYY) at 3 years postpartum among 570 participants with 3-year postpartum blood samples (178 fasting), prospectively collected lactation history, and no intervening pregnancy in Project Viva, a cohort study of mothers and children.

RESULTS

A total of 88% of mothers had initiated breastfeeding, 26% had breastfed ≥ 12 months, and 42% had exclusively breastfed for ≥ 3 months. In multivariate analyses, we found that duration of total breastfeeding was directly related to PYY and ghrelin, and exclusive breastfeeding duration was directly related to ghrelin (predicted mean for never exclusively breastfeeding: 790.6 pg/mL vs. ≥ 6 months of exclusive breastfeeding: 1,008.1 pg/mL; P < 0.01) at 3 years postpartum, adjusting for pregravid BMI, gestational weight gain, family history of diabetes, parity, smoking status, and age. We found a nonlinear pattern of association between exclusive breastfeeding duration and adiponectin in multivariate-adjusted models.

CONCLUSIONS

In this prospective cohort study, we found a direct relationship between the duration of lactation and both ghrelin and PYY at 3 years postpartum.

Preventing postpartum depression

Major depression is a frequent complication of the postpartum period. Untreated postpartum depression increases the risk of maternal suicide and can impair parenting capability with resultant adverse effects on offspring development. A number of factors influence a woman's vulnerability to postpartum depressive episodes. This article summarizes processes for assessing these risk factors and implementing primary preventive interventions, and summarizes methods of early detection to promote secondary and tertiary prevention.