I love you from the bottom of my hypothalamus: The role of stress physiology in romantic pair bond formation and maintenance

The relationship of coping style and social support variation to glucocorticoid metabolites in wild olive baboons (Papio anubis)

Social support, via investment in relationships of importance with others, is often emphasized as a pathway towards mediating stress. The effectiveness of social support, however, can be altered by personality differences, but the physiological consequences of such covariation are still poorly explored. How do individual differences in the functioning of the stress response system mediate access to, and use of, social support? To examine this dynamic, we investigated glucocorticoids as a biomarker of energetic activation that may also be activated by chronic psychosocial stress. For this purpose, we studied a wild anthropoid primate, i.e. the olive baboon (Papio anubis), for 17 months, in Laikipia District, Kenya. We measured biomarkers of energetic activation, i.e., fecal glucocorticoid metabolites (fGCms), to address whether individual differences in stress coping and social support were associated with variation in hormone levels across a period from 2018 to 2019. We found evidence for an association between social support and fGCm concentrations. This association had a discernable interaction between sex and social support: we found a negative association in male baboons, relative to females-who did not have a pronounced effect. Our findings emphasize the importance of social support in male baboons. The cost of not having diverse bonds, has been downplayed in male baboons.

Family risk, parental cortisol contagion, and parenting: A process-oriented approach to spillover

This multi-method longitudinal study sought to investigate linkage in parental neuroendocrine functioning - indicated by cortisol - over two measurement occasions. In addition, we examined how parental cortisol linkage may operate as an intermediate factor in the cascade of contextual risks and parenting. Participants were 235 families with a young child (Mage = 33.56, 36.00 years for mothers and fathers respectively), who were followed for two annual measurement occasions. Parental cortisol linkage was measured around a laboratory conflict discussion task at both measurement occasions (i.e., pre-discussion, 20- and 40-minute post-discussion for each measurement occasion). Maternal and paternal parenting behavior was observed during a parent-child discipline discussion task. Findings indicated similar levels of cortisol linkage between parents over the two measurement occasions. Furthermore, cortisol linkage between parents operated as an intermediate factor between contextual risks and more compromised parenting behavior. That is, greater contextual risks, indicated by greater neighborhood risk and interparental conflict, were linked to greater cortisol linkage between parents over time, which was in turn linked to greater authoritarian parenting during parent-child interaction. Findings highlighted the importance of understanding physiological-linkage processes with respect to the impact of contextual risks on family functioning and may have crucial implications for clinical work.

Deviations in stress and support: Associations with parenting emotions across the COVID-19 pandemic

Stress is a potent disruptor of parents' emotional well-being and interactions with their children. In the context of the early months of the unfolding pandemic, parents' stress likely fluctuated, with downstream impacts on their parenting experiences. The sample consisted of 72 Latina mothers who participated in a 15-20-min phone interview roughly once a month between March 2020 and January 2021. Mothers were asked about their experiences of stress, the quality of partner support, and their emotional experience of parenting. Analyses revealed that mothers' experiences of stress were high at the beginning of the pandemic and slowly decreased as time went on, though this decline eventually leveled off. Partner support and mothers' emotional experiences of parenting, on the other hand, did not change across the first 10 months of the pandemic. Collectively, the within and between analyses revealed that stress (individually), and stress and support (interactively) were associated with mothers' emotional experiences while interacting with their children. Between-subjects analyses revealed greater stress was associated with greater negative emotions during parenting, though support did not buffer this association. Within-subjects analyses revealed a quadratic association between stress and positive parenting emotions, such that at lower levels of stress, increases in stress were associated with more positive than typical emotions during parenting. However, the inclusion of social support into the model as a moderator revealed that when mothers received less support than typical from their partners, mothers' greater experience of stress was associated with their greater experience of negativity during parent-child interactions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Functional Neuroimaging of Human Hypothalamus in Socioemotional Behavior: A Systematic Review

There exist extensive animal research and lesion studies in humans demonstrating a tight association between the hypothalamus and socioemotional behavior. However, human neuroimaging literature in this direction is still rather limited. In order to reexamine the functional role of this region in regulating human social behavior, we here provided a synthesis of neuroimaging studies showing hypothalamic activation during affiliative, cooperative interactions, and in relation to ticklish laughter and humor. In addition, studies reporting involvement of the hypothalamus during aggressive and antisocial interactions were also considered. Our systematic review revealed a growing number of investigations demonstrating that the evolutionary conserved hypothalamic neural circuity is involved in multiple and diverse aspects of human socioemotional behavior. On the basis of the observed heterogeneity of hypothalamus-mediated socioemotional responses, we concluded that the hypothalamus might play an extended functional role for species survival and preservation, ranging from exploratory and approaching behaviors promoting social interactions to aggressive and avoidance responses protecting and defending the established social bonds.

Closeness-inducing discussions with a romantic partner increase cortisol and testosterone

Despite progress in understanding the social neuroendocrinology of close relationship processes, most work has focused on negative experiences, such as relationship conflict or stress. As a result, much less is known about the neuroendocrine implications of positive, emotionally intimate relationship experiences. In the current study, we randomly assigned 105 dating or married couples to a 30-minute semi-structured discussion task that was designed to elicit either high or low levels of closeness. Participants provided pre- and post-task saliva samples (to assess cortisol and testosterone) and post-task reports of self-disclosure, closeness, attraction, positive and negative affect, and stress. Participants found the discussion conditions comparably positive and enjoyable, but those in the high-closeness condition reported that they disclosed marginally more and felt marginally closer to their partners than those in the low-closeness condition. Participants also showed larger increases in cortisol and testosterone during the high (versus low) closeness discussion, and self-reported disclosure mediated these increases in cortisol and testosterone. Self-reported closeness and other theoretically plausible mediators, such as sexual attraction and excitement, did not mediate changes in either hormone. Taken together, the current findings contribute to our understanding of neuroendocrine changes associated with emotionally intimate relationship experiences. We consider possible explanations for the hormone changes we observed and offer directions for future research on the neuroendocrine implications of close relationship experiences.

Proximate and Ultimate Perspectives on Romantic Love

Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

Calming Effects of Touch in Human, Animal, and Robotic Interaction-Scientific State-of-the-Art and Technical Advances

Small everyday gestures such as a tap on the shoulder can affect the way humans feel and act. Touch can have a calming effect and alter the way stress is handled, thereby promoting mental and physical health. Due to current technical advances and the growing role of intelligent robots in households and healthcare, recent research also addressed the potential of robotic touch for stress reduction. In addition, touch by non-human agents such as animals or inanimate objects may have a calming effect. This conceptual article will review a selection of the most relevant studies reporting the physiological, hormonal, neural, and subjective effects of touch on stress, arousal, and negative affect. Robotic systems capable of non-social touch will be assessed together with control strategies and sensor technologies. Parallels and differences of human-to-human touch and human-to-non-human touch will be discussed. We propose that, under appropriate conditions, touch can act as (social) signal for safety, even when the interaction partner is an animal or a machine. We will also outline potential directions for future research and clinical relevance. Thereby, this review can provide a foundation for further investigations into the beneficial contribution of touch by different agents to regulate negative affect and arousal in humans.

Cortisol Synchrony in Older Couples: Daily Socioemotional Correlates and Interpersonal Differences

OBJECTIVE

Social relationships can have positive and negative influences, and these associations are particularly pronounced in old age. This study focuses on everyday interpersonal physiological dynamics (cortisol synchrony) in older couples and investigates its associations with partner presence, positive daily partner interactions, and empathy.

METHODS

We conducted coordinated multilevel analyses using data from two samples of older couples from Vancouver, Canada, and Berlin, Germany (study 1: n = 85 couples aged 60-87 years; study 2: n = 77 couples aged 66-85 years), who completed questionnaires and provided salivary cortisol samples five to seven times daily for 7 days.

RESULTS

Significant dyadic covariation in cortisol (synchrony) was present across studies (study 1/2: b = 0.04/0.03, p < .001/.001). Partner presence was only associated with greater cortisol synchrony in study 1 (b = 0.06, p = .003) but not in study 2 (b = 0.02, p = .187). Cortisol synchrony was higher when partners reported prior positive socioemotional partner interactions (study 1: b = 0.09, p = .005; study 2: b = 0.04, p = .005). There was no statistically significant association between cortisol synchrony and empathic concern (b = 0.01, p = .590) or perspective taking (b = 0.02, p = .065).

CONCLUSIONS

Moments of social bonding are intertwined with physiological synchrony in everyday life. The implications of potential repeated transmission of stress in the context of high synchrony for individual health and relationship functioning warrant further investigation.

Morphofunctional Alterations of the Hypothalamus and Social Behavior in Autism Spectrum Disorders

An accumulating body of evidence indicates a tight relationship between the endocrine system and abnormal social behavior. Two evolutionarily conserved hypothalamic peptides, oxytocin and arginine-vasopressin, because of their extensively documented function in supporting and regulating affiliative and socio-emotional responses, have attracted great interest for their critical implications for autism spectrum disorders (ASD). A large number of controlled trials demonstrated that exogenous oxytocin or arginine-vasopressin administration can mitigate social behavior impairment in ASD. Furthermore, there exists long-standing evidence of severe socioemotional dysfunctions after hypothalamic lesions in animals and humans. However, despite the major role of the hypothalamus for the synthesis and release of oxytocin and vasopressin, and the evident hypothalamic implication in affiliative behavior in animals and humans, a rather small number of neuroimaging studies showed an association between this region and socioemotional responses in ASD. This review aims to provide a critical synthesis of evidences linking alterations of the hypothalamus with impaired social cognition and behavior in ASD by integrating results of both anatomical and functional studies in individuals with ASD as well as in healthy carriers of oxytocin receptor (OXTR) genetic risk variant for ASD. Current findings, although limited, indicate that morphofunctional anomalies are implicated in the pathophysiology of ASD and call for further investigations aiming to elucidate anatomical and functional properties of hypothalamic nuclei underlying atypical socioemotional behavior in ASD.

Social Allostasis and Social Allostatic Load: A New Model for Research in Social Dynamics, Stress, and Health

Theories such as social baseline theory have argued that social groups serve a regulatory function but have not explored whether this regulatory process carries costs for the group. Allostatic load, the wear and tear on regulatory systems caused by chronic or frequent stress, is marked by diminished stress system flexibility and compromised recovery. We argue that allostatic load may develop within social groups as well and provide a model for how relationship dysfunction operates. Social allostatic load may be characterized by processes such as groups becoming locked into static patterns of interaction and may ultimately lead to up-regulation or down-regulation of a group's set point, or the optimal range of arousal or affect around which the group tends to converge. Many studies of emotional and physiological linkage within groups have reported that highly correlated states of arousal, which may reflect failure to maintain a group-level regulatory baseline, occur in the context of stress, conflict, and relationship distress. Relationship strain may also place greater demands on neurocognitive regulatory processes. Just as allostatic load may be detrimental to individual health, social allostatic load may corrode relationship quality.

Hormones in speed-dating: The role of testosterone and cortisol in attraction

There is evidence that testosterone and cortisol levels are related to the attraction of a romantic partner; testosterone levels relate to a wide range of sexual behaviors and cortisol is a crucial component in the response to stress. To investigate this, we conducted a speed-dating study among heterosexual singles. We measured salivary testosterone and cortisol changes in men and women (n = 79) when they participated in a romantic condition (meeting opposite-sex others, i.e., potential romantic partners), as well as a control condition (meeting same-sex others, i.e., potential friends). Over the course of the romantic speed-dating event, results showed that women's but not men's testosterone levels increased and cortisol levels decreased for both men and women. These findings indicate that men's testosterone and cortisol levels were elevated in anticipation of the event, whereas for women, this appears to only be the case for cortisol. Concerning the relationship between attraction and hormonal change, four important findings can be distinguished. First, men were more popular when they arrived at the romantic speed-dating event with elevated cortisol levels. Second, in both men and women, a larger change in cortisol levels during romantic speed-dating was related to more selectivity. Third, testosterone alone was unrelated to any romantic speed-dating outcome (selectivity or popularity). However, fourth, women who arrived at the romantic speed-dating event with higher testosterone levels were more selective when their anticipatory cortisol response was low. Overall, our findings suggest that changes in the hormone cortisol may be stronger associated with the attraction of a romantic partner than testosterone.

Romantic Love and Reproductive Hormones in Women

Increased reproductive success is among the most commonly proposed adaptive functions of romantic love. Here, we tested if hormonal changes associated with falling in love may co-vary with hormonal profiles that predict increased fecundity in women. We compared blood serum levels of estradiol (E2, E2/T), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), free testosterone (fT), and cortisol (CT), measured in the early follicular phase of the menstrual cycle in single women (N = 69) and in women at the beginning of a romantic heterosexual relationship who reported being in love with their partner (N = 47). Participants were healthy, regularly cycling women aged 24 to 33 who did not use hormonal contraception. We found that women in love had higher levels of gonadotropins (FSH, LH) and lower testosterone levels compared to single women who were not in love. These groups of women did not, however, differ in terms of estradiol, prolactin, or cortisol levels.

Adrenocortical and autonomic attunement between romantic partners in emerging adulthood

Parent-child physiological attunement, particularly during stressful situations, appears adaptive as shared stress reactivity may promote dyadic engagement. Romantic partners eventually replace parents as the primary support figure, yet it remains unclear whether romantic partners buffer physiological stress or display physiological attunement as most studies on adults examine attunement during conflict paradigms. The present study examined physiological attunement in 63 emerging adult romantic partner dyads (one partner was the active participant, the other the observer) during the Trier Social Stress Task (TSST). Heart rate (HR) and respiratory sinus arrhythmia (RSA) were continuously monitored across the visit. Repeated saliva samples were assayed for cortisol. Physiological attunement was operationalized as a correlation in biomarkers between the TSST participant and their partner; sex, social support, and physical proximity were examined as moderators. We then compared the biomarker profiles of partnered-TSST participants to individuals who participated in the TSST solo (n = 63) to determine if partner presence buffered stress biomarker reactivity during the TSST. RSA attunement between partners was found but was not further moderated by social support or sex. Adrenocortical attunement was moderated, such that lower social support and increased proximity resulted in higher attunement. HR attunement was higher when the participant was male and when partners were in close physical proximity. Compared to TSST solo, romantic partner presence increased participant cortisol levels and altered HR reactivity, suggesting that emerging adult romantic partners do not buffer physiological stress reactivity. Future research should examine whether physiological attunement and partner presence is protective in more established relationships.

Marital Conflict Predicts Mother-to-Infant Adrenocortical Transmission

Employing an experimental design, mother-to-infant transmission of stress was examined. Mothers (N = 117) were randomized to either have a positive or conflictual discussion with their marital partners, after which infants (age = 6 months) participated in a fear and frustration task. Saliva samples were collected to assess maternal cortisol responses to the discussion and infant cortisol responses to the challenge task. Results indicate maternal cortisol reactivity and recovery to the conflict (but not positive) discussion predicted infant cortisol reactivity to the infant challenge. Mothers' positive affect during the discussion buffered, and intrusion during the free-play potentiated, mother-to-infant adrenocortical transmission. These findings advance our understanding of the social and contextual regulation of adrenocortical activity in early childhood.