Eating to live well-Or worse? The role of vegan and vegetarian diets in mental health

BACKGROUND

Over the past two decades, there has been an increase in the prevalence of psychological conditions, such as depression, anxiety, disordered eating, and body image disturbances. In concert with this trend, there was a substantial rise in the advocacy and practice of restrictive dietary patterns, such as veganism and vegetarianism. These parallel developments suggest a relation between diet and mental health, but to date, research has failed to offer clear answers on whether these associations are causal, coincidental, or more complex than superficial analyses suggest.

AIM

Given this context, the purpose of this commentary is to offer a consilient perspective on the role of vegan and vegetarian diets in mental health.

METHODS

We performed a broad qualitative synthesis of the current literature on diet and mental health from sociologic and psychologic perspectives.

RESULTS

Several empirically supported hypotheses were presented with equivocal support.

CONCLUSION

The current evidence suggests that if a nutritionally adequate diet is consumed, the avoidance/consumption of meat and other animal foods will have no significant effects on physical and mental health.

Depression in adolescence and young adulthood: the difficulty to integrate motivational/emotional systems

Depression is presented as a multi-factorial bio-psycho-social expression that has evolved primarily as an effect of stressors related to the motivational/emotional systems that regulate the BrainMind in our relationship with conspecifics. These stressors may be caused by two sources of threat, firstly, the loss of bonding with the caregiver and later with a partner and/or group which relates to the SEPARATION (PANIC/GRIEF) system, secondly, social defeat as an expression of the social competition and social dominance. The sexual maturity drives the individual to social competition and social dominance, even if the latter often occurs before sexual maturity, e.g., chickens, dogs, non-human primates, and humans. Depression is an evolutionarily conserved mechanism in mammals to terminate both separation anxiety, so as to protect the vulnerable social brain from the consequences of prolonged separation anxiety, and the stress of social competition when social defeat is predictable. Adolescence and Young adulthood are particularly susceptible to these two types of threat because of human developmental characteristics that are summarized by the term neoteny. This refers to the slowing down of growth and development, resulting in both a prolonged period of dependence on a caring/protective adult and the persistence of juvenile characteristics throughout life. Therefore, neoteny makes the transition from childhood to sexual maturity more dramatic, making the integration of the SEPARATION (PANIC/GRIEF) system with the dynamics of social competition and dominance more stressful and a source of depression. Stress is an expression of the HPA-Hypothalamic-Pituitary-Adrenal axis that articulates with other systems, mainly the autonomic nervous system and the immune-inflammatory system. The latter is believed to be one of the most significant components in the dynamics of depressive processes, connected to the prodromes of its activation in childhood, under the pressure of environmental and relational stressors which can lead to learned helplessness. The recurrence of stressors makes it easier for the immune-inflammatory system to be activated in later life, which could make a significant contribution to the establishment of a depressive disease. The possible contribution of children's identification processes with their parents' depressive personalities through observational learning is considered.

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.

Measuring empathic stress - A systematic review of methodology and practical considerations for future research

Aside from stressors that each of us experience directly, we also share the stress of the people around us. Such empathic stress exists on psychological and physiological levels, including subjective, sympathetic, parasympathetic and endocrine activation. The objective of this review is to offer an overview of methodology over the past fifteen years of empathic stress research and derive practical considerations for future research endeavors in the field. We used a keyword search strategy in the databases Web of Science, PsycInfo and PubMed to find empathic stress studies published until December 2023, and included 17 studies into our review. The reviewed laboratory studies provide initial yet consistent evidence for the existence of empathic stress across different populations, in intimate and stranger dyads, with direct and virtual contact, across multiple levels of the stress system, and based on diverse statistical analysis methods. We discuss all findings and derive practical considerations for future empathic stress research. The diversity of methods established provides a solid foundation upon which future studies can expand.

Mitochondrial Functioning: Front and Center in Defining Psychosomatic Mechanisms of Allostasis in Health and Disease

There is increased awareness among basic and clinical scientists that psychological and social stress can have detrimental effects on physical, cognitive, and mental health. Data have been published indicating that social, economic, psychological, and physical environmental stress can influence behavior that has biological and physiological consequences-yet there are major gaps in understanding the physiological and cellular processes that drive increased morbidity and mortality. The potential role of mitochondria has been highlighted in psychosomatic medicine, as their functionality in various biological and physiological processes has earned recognition. This review outlines the essential role of mitochondria by considering the numerous intracellular, extracellular, and physiological functions it regulates that position the organelle as a central mediator in responses to psychological stress. We then connect these functions to mitochondrial allostasis and allostatic load for further examination of the limitations of mitochondria to an adaptive psychological stress response where mitochondrial allostatic load may eventually lead to systemic pathophysiology. This review emphasizes how chronic social, economic, and psychological stress can contribute to mitochondrial dysfunction and predispose individuals to poorer health outcomes and death. Mitochondrial capacity, function, and activity may therefore serve as biomarkers for identifying individuals at high risk for developing comorbid conditions related to their psychosocial environment.

Chronic social stressors and striatal dopamine functioning in humans: A systematic review of SPECT and PET studies

The dopamine hypothesis of schizophrenia posits that elevated striatal dopamine functioning underlies the development of psychotic symptoms. Chronic exposure to social stressors increases psychosis risk, possibly by upregulating striatal dopamine functioning. Here we systematically review single photon emission computed tomography (SPECT) and positron emission tomography (PET) studies that examined the relationship between chronic social stress exposure and in vivo striatal dopamine functioning in humans. We searched the scientific databases PubMed and PsycINFO from inception to August 2023. The quality of the included studies was evaluated with the ten-item Observational Study Quality Evaluation (PROSPERO: CRD42022308883). Twenty-eight studies were included, which measured different aspects of striatal dopamine functioning including dopamine synthesis capacity (DSC), vesicular monoamine transporter type 2 binding, dopamine release following a pharmacological or behavioral challenge, D2/3 receptor binding, and dopamine transporter binding. We observed preliminary evidence of an association between childhood trauma and increased striatal DSC and dopamine release. However, exposure to low socioeconomic status, stressful life events, or other social stressors was not consistently associated with altered striatal dopamine functioning. The quality of available studies was generally low. In conclusion, there is insufficient evidence that chronic social stressors upregulate striatal dopamine functioning in humans. We propose avenues for future research, in particular to improve the measurement of chronic social stressors and the methodological quality of study designs.

Oxidative stress in the brain is regulated by social status in a highly social cichlid fish

Social stress can increase reactive oxygen species and derail antioxidant function in the brain, which may contribute to the onset and progression of mental health disorders. In hierarchical species, repeated social defeat can raise oxidative stress in the brain. However, how oxidative balance in the brain is regulated across different levels in a social hierarchy is unknown. Here, we study the effect of social status on patterns of oxidative stress across several brain divisions in a highly social cichlid fish, Astatotilapia burtoni. In this species, dominant males are territorial, brightly colored, and reproductively active while subordinate males are not. We measured several markers of oxidative stress in macrodissected brain divisions in dominant and subordinate males. We found that dominant individuals had lower oxidative DNA damage (8-OhdG) in the midbrain while also having increased total antioxidant capacity in the midbrain and hypothalamus. However, in dominant males, oxidative DNA damage tended to be higher in the hypothalamus while total glutathione levels were lower in the telencephalon compared to subordinate males. Finally, we found that indicators of reproductive activity (gonadosomatic index and social behavior) were co-regulated with antioxidant function or oxidative damage in the telencephalon. Combined, our results suggest that social status and activation of the reproductive system regulate oxidative balance in the brain in a highly brain division specific manner.

Changes in social environment impact primate gut microbiota composition

BACKGROUND

The gut microbiota (GM) has proven to be essential for both physical health and mental wellbeing, yet the forces that ultimately shape its composition remain opaque. One critical force known to affect the GM is the social environment. Prior work in humans and free-ranging non-human primates has shown that cohabitation and frequent social interaction can lead to changes in GM composition. However, it is difficult to assess the direction of causation in these studies, and interpretations are complicated by the influence of uncontrolled but correlated factors, such as shared diet.

RESULTS

We performed a 15-month longitudinal investigation wherein we disentangled the impacts of diet and social living conditions on GM composition in a captive cohort of 13 male cynomolgus macaques. The animals were in single housing for the first 3 months of the study initially with a variable diet. After baseline data collection they were placed on a controlled diet for the remainder of the study. Following this diet shift the animals were moved to paired housing for 6 months, enabling enhanced social interaction, and then subsequently returned to single housing at the end of our study. This structured sequencing of diet and housing changes allowed us to assess their distinct impacts on GM composition. We found that the early dietary adjustments led to GM changes in both alpha and beta diversity, whereas changes in social living conditions only altered beta diversity. With respect to the latter, we found that two particular bacterial families - Lactobacillaceae and Clostridiaceae - demonstrated significant shifts in abundance during the transition from single housing to paired housing, which was distinct from the shifts we observed based on a change in diet. Conversely, we found that other bacteria previously associated with sociality were not altered based on changes in social living conditions but rather only by changes in diet.

CONCLUSIONS

Together, these findings decouple the influences that diet and social living have on GM composition and reconcile previous observations in the human and animal literatures. Moreover, the results indicate biological alterations of the gut that may, in part, mediate the relationship between sociality and wellbeing.

Elite class self-interest, socioeconomic inequality and U.S. population health

Class-based perspectives on the persistent social gradients in health within modern welfare states largely focus on the adverse consequences of unfettered neoliberalism and entrenched meritocratic socioeconomic selection. Namely, neoliberal-driven economic inequality has fuelled resentment and stress among lower-status groups, while these groups have become more homogeneous with regard to health behaviours and outcomes. We synthesise several sociological and historical literatures to argue that, in addition to these class-based explanations, socioeconomic inequality may contribute to persistent social gradients in health due to elite class self-interest-in particular elites' preferences for overdiagnosis, overprescription and costly high-technology medical treatments over disease prevention, and for increased tolerance for regulatory capture. We demonstrate that this self-interest provides parsimonious explanations for several contemporary trends in U.S. health inequality including (A) supply-side factors in drug-related deaths, (B) longitudinal trends in the social gradients of obesity and chronic disease mortality and (C) the immigrant health advantage. We conclude that sociological theories of elite class self-interest usefully complement theories of the psychosocial effects of neoliberalism and of meritocratic social selection while answering recent calls for research on the role advantaged groups play in generating inequalities in health, and for research that moves beyond technological determinism in health sociology.

Extrinsic goals benefit capitalism but not well-being. Rethinking the economy's goal for a healthier future

The dramatic rise in non-communicable diseases around the world but notably in high-income countries like the UK is a manifestation of a global economic system-capitalism-that prioritizes wealth over health. A decade ago, the former WHO Director-General, Margaret Chan highlighted how 'efforts to prevent non-communicable diseases go against the business interests of powerful economic operators' [United Nations. (2013) Take Action for the Sustainable Development Goals. https://www.un.org/sustainabledevelopment/sustainable-development-goals/ (last accessed 16 February 2024)]. While there is a growing literature on how politics and economics influence population health-for better or worse-less attention has been given to exploring how economic systems like capitalism influence people's psychological well-being. To fill this gap, the following article examines how the continued pursuit of economic growth under capitalism (neoliberal free-market forms especially) impacts well-being through challenging basic psychological needs for security, autonomy, competence and relatedness. In doing so, I hope to shed important light on the sources and possible solutions to our growing health and social problems, and stimulate a conversation on how to achieve a healthier future for us all.

Is Redistribution Good for Our Health? Examining the Macrocorrelation between Welfare Generosity and Health across EU Nations over the Last 40 Years

CONTEXT

Social determinants of health are finally getting much-needed policy attention, but their political origins remain underexplored. In this article, the authors advance a theory of political determinants as accruing along three pathways of welfare state effects (redistribution, poverty reduction, and status preservation), and they test these assumptions by examining impacts of policy generosity on life expectancy (LE) over the last 40 years.

METHODS

The authors merge new and existing welfare policy generosity data from the Comparative Welfare Entitlement Project with data on LE spanning 1980-2018 across 21 countries in the Organization for Economic Cooperation and Development. They then examine relationships between five welfare policy generosity measures and LE using cross-sectional differencing and autoregressive lag models.

FINDINGS

The authors find consistent and positive effects for total generosity (an existing measure of social insurance generosity) on LE at birth across different model specifications in the magnitude of an increase in LE at birth of 0.10-0.15 years (p < 0.05) as well as for a measure of status preservation (0.11, p < 0.05). They find less consistent support for redistribution and poverty reduction measures.

CONCLUSIONS

The authors conclude that in addition to generalized effects of policy generosity on health, status-preserving social insurance may be an important, and relatively overlooked, mechanism in increasing LE over time in advanced democracies.

How infants predict respect-based power

Research has shown that infants represent legitimate leadership and predict continued obedience to authority, but which cues they use to do so remains unknown. Across eight pre-registered experiments varying the cue provided, we tested if Norwegian 21-month-olds (N=128) expected three protagonists to obey a character even in her absence. We assessed whether bowing for the character, receiving a tribute from or conferring a benefit to the protagonists, imposing a cost on them (forcefully taking a resource or hitting them), or relative physical size were used as cues to generate the expectation of continued obedience that marks legitimate leadership. Whereas bowing sufficed in generating such an expectation, we found positive Bayesian evidence that all the other cues did not. Norwegian infants unlikely have witnessed bowing in their everyday life. Hence, bowing/prostration as cue for continued obedience may form part of an early-developing capacity to represent leadership built by evolution.

Evidence for differential associations of distinct trait mindfulness facets with acute and chronic stress

Stress and stress-associated disease are considered the health epidemic of the 21st century. Interestingly, despite experiencing similar amounts of stress than those falling ill, some individuals are protected against the "wear and tear of daily life". Based on the notion that mindfulness training strengthens stress resilience, we explored whether facets of trait mindfulness, prior to training intervention, are linked to acute psychosocial stress reactivity and chronic stress load. To assess different mindfulness facets, over 130 participants completed the Five Facet Mindfulness Questionnaire (FFMQ) and the Freiburg Mindfulness Inventory (FMI). For acute stress induction, a standardized psychosocial stress test was conducted. Subjective stress, sympathetic and parasympathetic activity, and levels of the hypothalamic-pituitary-adrenal axis end hormone cortisol were assessed repeatedly. Additionally, levels of hair cortisol and cortisone as indices of the long-term physiological stress load were collected. We found differential associations of different facets of mindfulness with subjective stress, cortisol, and hair cortisone levels. Specifically, the trait mindfulness facets FMI "Acceptance" and the ability to put one's inner experience into words (FFMQ "Describing") were associated with lower acute subjective and cortisol stress reactivity. Contrarily, monitoring-related trait mindfulness facets (FFMQ "Acting with Awareness" and "Observing") were associated with higher acute cortisol and marginally higher long-term cortisone release. Our results suggest granularity of the mindfulness construct. In accordance with the "Monitor and Acceptance Theory", especially acceptance-related traits buffered against stress, while monitoring-related traits seemed to be maladaptive in the context of stress. The current results give valuable guidance for the conceptualization of mindfulness-based interventions geared towards stress reduction.

Manipulation of a social signal affects DNA methylation of a stress-related gene in a free-living bird

Social status directly affects the health of humans and other animals. Low status individuals receive more antagonistic encounters, have fewer supportive relationships and have worse health outcomes. However, the physiological and cellular processes that mediate the relationship between the social environment and health are incompletely known. Epigenetic regulation of the hypothalamic-pituitary-adrenal (HPA) axis, the neuroendocrine pathway that activates in response to stressors, may be one process that is sensitive to the social environment. Here, we experimentally manipulated plumage, a key social signal in female tree swallows (Tachycineta bicolor) and quantified methylation of four genes in the HPA axis before and after treatment. We found that dulling the white breast plumage affected methylation in one gene, CRHR1; however, the effect depended on the original brightness of the bird. Methylation in this gene was correlated with baseline corticosterone levels, suggesting that DNA methylation of CRHR1 helps regulate glucocorticoid production in this species. Methylation in two other genes, FKBP5 and GR, changed over the course of the experiment, independent of treatment. These results show that methylation of these genes is labile into adulthood and suggest that epigenetic regulation of the HPA axis could help birds respond to current environmental conditions.

Independent fitness consequences of group size variation in Verreaux's sifakas

The costs and benefits of group living are also reflected in intraspecific variation in group size. Yet, little is known about general patterns of fitness consequences of this variation. We use demographic records collected over 25 years to determine how survival and reproductive success vary with group size in a Malagasy primate. We show that female reproductive rates of Verreaux's sifakas (Propithecus verreauxi) are not affected by total group size, but that they are supressed by the number of co-resident females, whereas mortality rates are significantly higher in larger groups. Neither annual rainfall nor the adult sex ratio have significant effects on birth and death rates. Hence, these sifakas enjoy the greatest net fitness benefits at small, and not the predicted intermediate group sizes. Thus, independent fitness proxies can vary independently as a function of group size as well as other factors, leading to deviations from optimal intermediate group sizes.

Income rank and depressive symptoms among employees in Germany - A 5-year cross-lagged panel analysis

Background/Objective

Socioeconomic disparities in mental health are well-established. Previous research suggests that relative income rank is associated with depressive symptoms above and beyond absolute income. This study aimed to investigate the predictive value of income rank for future depressive symptoms while accounting for absolute income. Exploring potential reverse pathways from depressive symptoms to income rank was a secondary objective.

Method

A two-wave cross-lagged panel design with a 5-year follow-up was used to analyze data for income rank, absolute income, and two dimensions of depressive symptoms (i.e., cognitive-affective and somatic symptoms) from initially 4,201 employees. Income rank was calculated for reference groups, based on the same gender, the same 5-year age band, and the same occupational skill level.

Results

Lower income rank at baseline predicted a higher severity of cognitive-affective depressive symptoms at five-year follow-up, even after adjusting for absolute income. In contrast, income rank did not demonstrate a significant unique longitudinal association with somatic depressive symptoms when simultaneously taking absolute income into account. There was no evidence for the assumption that depressive symptoms are predictive for future income rank (i.e., reverse pathway).

Conclusions

Cognitive-affective symptoms of depression might be particularly responsive to social comparisons and a relatively low social rank.

Mapping pathways to neuronal atrophy in healthy, mid-aged adults: From chronic stress to systemic inflammation to neurodegeneration?

Growing evidence implicates systemic inflammation in the loss of structural brain integrity in natural ageing and disorder development. Chronic stress and glucocorticoid exposure can potentiate inflammatory processes and may also be linked to neuronal atrophy, particularly in the hippocampus and the human neocortex. To improve understanding of emerging maladaptive interactions between stress and inflammation, this study examined evidence for glucocorticoid- and inflammation-mediated neurodegeneration in healthy mid-aged adults. N = 169 healthy adults (mean age = 39.4, 64.5% female) were sampled from the general population in the context of the ReSource Project. Stress, inflammation and neuronal atrophy were quantified using physiological indices of chronic stress (hair cortisol (HCC) and cortisone (HEC) concentration), systemic inflammation (interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP)), the systemic inflammation index (SII), hippocampal volume (HCV) and cortical thickness (CT) in regions of interest. Structural equation models were used to examine evidence for pathways from stress and inflammation to neuronal atrophy. Model fit indices indicated good representation of stress, inflammation, and neurological data through the constructed models (CT model: robust RMSEA = 0.041, robust χ2 = 910.90; HCV model: robust RMSEA <0.001, robust χ2 = 40.95). Among inflammatory indices, only the SII was positively associated with hair cortisol as one indicator of chronic stress (β = 0.18, p < 0.05). Direct and indirect pathways from chronic stress and systemic inflammation to cortical thickness or hippocampal volume were non-significant. In exploratory analysis, the SII was inversely related to mean cortical thickness. Our results emphasize the importance of considering the multidimensionality of systemic inflammation and chronic stress, with various indicators that may represent different aspects of the systemic reaction. We conclude that inflammation and glucocorticoid-mediated neurodegeneration indicated by IL-6 and hs-CRP and HCC and HEC may only emerge during advanced ageing and disorder processes, still the SII could be a promising candidate for detecting associations between inflammation and neurodegeneration in younger and healthy samples. Future work should examine these pathways in prospective longitudinal designs, for which the present investigation serves as a baseline.

Social niche shapes social behavior and cortisol concentrations during adolescence in female guinea pigs

Individualized social niches arise in social groups, resulting in divergent social behavior profiles among group members. During sensitive life phases, the individualized social niche can profoundly impact the development of social behavior and associated phenotypes such as hormone (e.g. cortisol) concentrations. Focusing on adolescence, we investigated the relationship between the individualized social niche, social behavior, and cortisol concentrations (baseline and responsiveness) in female guinea pigs. Females were pair-housed in early adolescence (initial social pair formation), and a social niche transition was induced after six weeks by replacing the partner with either a larger or smaller female. Regarding social behavior, dominance status was associated with aggression in both the initial social pairs and after the social niche transition, and the results suggest that aggression was rapidly and completely reshaped after the social niche transition. Meanwhile, submissive behavior was rapidly reshaped after the social niche transition, but this was incomplete. The dominance status attained in the initial social pair affected the extent of submissive behavior after the social niche transition, and this effect was still detected three weeks after the social niche transition. Regarding cortisol concentrations, higher baseline cortisol concentrations were measured in dominant females in the initial social pairs. After the social niche transition, cortisol responsiveness significantly increased for the females paired with a larger, older female relative to those paired with a smaller, younger female. These findings demonstrate that the social niche during adolescence plays a significant role in shaping behavior and hormone concentrations in females.

Association between social dominance hierarchy and PACAP expression in the extended amygdala, corticosterone, and behavior in C57BL/6 male mice

The natural alignment of animals into social dominance hierarchies produces adaptive, and potentially maladaptive, changes in the brain that influence health and behavior. Aggressive and submissive behaviors assumed by animals through dominance interactions engage stress-dependent neural and hormonal systems that have been shown to correspond with social rank. Here, we examined the association between social dominance hierarchy status established within cages of group-housed mice and the expression of the stress peptide PACAP in the bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). We also examined the relationship between social dominance rank and blood corticosterone (CORT) levels, body weight, motor coordination (rotorod) and acoustic startle. Male C57BL/6 mice were ranked as either Dominant, Submissive, or Intermediate based on counts of aggressive/submissive encounters assessed at 12 weeks-old following a change in homecage conditions. PACAP expression was significantly higher in the BNST, but not the CeA, of Submissive mice compared to the other groups. CORT levels were lowest in Submissive mice and appeared to reflect a blunted response following events where dominance status is recapitulated. Together, these data reveal changes in specific neural/neuroendocrine systems that are predominant in animals of lowest social dominance rank, and implicate PACAP in brain adaptations that occur through the development of social dominance hierarchies.

Social media does not elicit a physiological stress response as measured by heart rate and salivary cortisol over 20-minute sessions of cell phone use

The pervasive use of social media has raised concerns about its potential detrimental effects on physical and mental health. Others have demonstrated a relationship between social media use and anxiety, depression, and psychosocial stress. In light of these studies, we examined physiological indicators of stress (heart rate to measure autonomic nervous system activation and cortisol to assess activity of the hypothalamic-pituitary-adrenal axis) associated with social media use and investigated possible moderating influences of sex, age, and psychological parameters. We collected physiological data from 59 subjects ranging in age from 13 to 55 across two cell phone treatments: social media use and a pre-selected YouTube playlist. Heart rate was measured using arm-band heart rate monitors before and during cell phone treatments, and saliva was collected for later cortisol analysis (by enzyme immunoassay) before and after each of the two cell phone treatments. To disentangle the effects of cell phone treatment from order of treatment, we used a crossover design in which participants were randomized to treatment order. Our study uncovered a significant period effect suggesting that both heart rate and cortisol decreased over the duration of our experiment, irrespective of the type of cell phone activity or the order of treatments. There was no indication that age, sex, habits of social media use, or psychometric parameters moderated the physiological response to cell phone activities. Our data suggest that 20-minute bouts of social media use or YouTube viewing do not elicit a physiological stress response.

Female behavior drives the formation of distinct social structures in C57BL/6J versus wild-derived outbred mice in field enclosures

BACKGROUND

Social behavior and social organization have major influences on individual health and fitness. Yet, biomedical research focuses on studying a few genotypes under impoverished social conditions. Understanding how lab conditions have modified social organizations of model organisms, such as lab mice, relative to natural populations is a missing link between socioecology and biomedical science.

RESULTS

Using a common garden design, we describe the formation of social structure in the well-studied laboratory mouse strain, C57BL/6J, in replicated mixed-sex populations over 10-day trials compared to control trials with wild-derived outbred house mice in outdoor field enclosures. We focus on three key features of mouse social systems: (i) territory establishment in males, (ii) female social relationships, and (iii) the social networks formed by the populations. Male territorial behaviors were similar but muted in C57 compared to wild-derived mice. Female C57 sharply differed from wild-derived females, showing little social bias toward cage mates and exploring substantially more of the enclosures compared to all other groups. Female behavior consistently generated denser social networks in C57 than in wild-derived mice.

CONCLUSIONS

C57 and wild-derived mice individually vary in their social and spatial behaviors which scale to shape overall social organization. The repeatable societies formed under field conditions highlights opportunities to experimentally study the interplay between society and individual biology using model organisms.

Exploring discontinuous intentions of social media users: a cognition-affect-conation perspective

Introduction

Drawing on the cognition-affect-conation (C-A-C) framework, this study investigates how perceived information and social and system feature overload induce depression and anxiety, which leads to affect discontinuous intentions of the social media users.

Methods

The data collected from 570 social networking site users in China are analyzed through structural equation modeling (SEM).

Results and Discussion

The findings show that perceived information overload, perceived social overload, and perceived system feature overload directly affect depression and anxiety among social networking site users, which directly leads to discontinuous intentions. This study fulfills the identified need for an in-depth investigation of discontinuous behavior in social networking sites. The findings provide social networking site providers with guidelines on how to actively manage social networking site user's behavior to reduce the effects of negative emotions on social networking sites.

Whither dominance? An enduring evolutionary legacy of primate sociality

This article discusses dominance personality dimensions found in primates, particularly in the great apes, and how they compare to dominance in humans. Dominance traits are seen in virtually all primate species, and these dimensions reflect how adept an individual is at ascending within a social hierarchy. Among great apes, dominance is one of the most prominent personality factors but, in humans, dominance is usually modeled as a facet of extraversion. Social, cultural, and cognitive differences between humans and our closest ape relatives are explored, alongside humanity's hierarchical and egalitarian heritage. The basic characteristics of dominance in humans and nonhuman great apes are then described, alongside the similarities and differences between great apes. African apes live in societies each with its own hierarchical organization. Humans were a possible exception for some of our history, but more recently, hierarchies have dominated. The general characteristics of high-dominance humans, particularly those living in industrialized nations, are described. Dominance itself can be subdivided into correlated subfactors: domineering, prestige, and leadership. Various explanations have been posed for why dominance has declined in prominence within human personality factor structures, and several possibilities are evaluated. The value of dominance in personality research is discussed: dominance has links to, for instance, age, sex, aggression, self-esteem, locus of control, stress, health, and multiple socioeconomic status indicators. The piece concludes with recommendations for researchers who wish to assess dominance in personality.

Unraveling the social hierarchy: Exploring behavioral and neural dynamics in shaping inhibitory control

Inhibitory control is crucial for regulating emotions, suppressing biases, and inhibiting inappropriate responses in social interactions. Social rank, or perceived position in the hierarchy, can influence inhibitory control, with high-rank individuals requiring it to regulate dominant behavior and low-rank individuals requiring it to regulate emotional reactions or avoid submissive behaviors. Furthermore, research suggests that social status can affect the neural mechanisms underlying inhibitory control, leading to differences in abilities and strategies based on perceived rank. In this study, we investigated the effects of social rank on inhibitory control using a dot estimation task to prime social hierarchy. Subsequently, we assessed the inhibitory control of the participants using a Go/Nogo task with photos of individuals in different social ranks. The study recruited a total of 43 students (22 males and 21 females), with a mean age of 26.8 years (SD=4.08). We measured both behavioral (reaction time and response accuracy) and electrophysiological (N200 and P300 event-related potentials) responses to investigate the neural correlates of inhibitory control. Results showed that participants responded slower to lower-rank individuals but had higher accuracy when inhibiting their response to them. The N200 amplitude was greater when presented with higher ranks stimuli in Go trials, indicating greater conflict monitoring, while the P300 amplitude was significantly higher in Nogo trials compared to Go trials. These findings suggest that social rank can influence inhibitory control and highlight the importance of considering the impact of social hierarchy in social interactions.

Characterization of social hierarchy formation and maintenance in same-sex, group-housed male and female C57BL/6 J mice

Social hierarchies are a prevalent feature of all animal groups, and an individual's rank within the group can significantly affect their overall health, typically at the greatest expense of the lowest-ranked individuals, or omegas. These subjects have been shown to exhibit various stress-related phenotypes, such as increased hypothalamic-pituitary axis activity and increased amygdalar corticotropin-releasing factor levels compared to higher-ranked subjects. However, these findings have been primarily characterized in males and in models requiring exhibition of severe aggression. The goals of the current study, therefore, were to characterize the formation and maintenance of social hierarchies using the tube test and palatable liquid competition in same-sex groups of male and female C57BL/6 J mice. We also aimed to examine the effects of tube test-determined social rank on plasma and hypothalamic oxytocin and vasopressin levels, peptides with established roles in social behaviors and the stress response. Lastly, we assessed the effects of environmental enrichment and length of testing on the measures outlined above. Overall, we demonstrated that males and females develop social hierarchies and that these hierarchies can be determined using the tube test. While we were unable to establish a consistent connection between peptide levels and social rank, we observed transient changes in these peptides reflecting complex interactions between social rank, sex, environment, and length of testing. We also found that many male and female omegas began to exhibit passive coping behavior after repeated tube test losses, demonstrating the potential of this assay to serve as a model of chronic, mild psychosocial stress.

How behavioural ageing affects infectious disease

Ageing is associated with profound changes in behaviour that could influence exposure and susceptibility to infectious disease. As well as determining emergent patterns of infection across individuals of different ages, behavioural ageing could interact with, confound, or counteract age-related changes in other traits. Here, we examine how behavioural ageing can manifest and influence patterns of infection in wild animals. We discuss a range of age-related changes that involve interactions between behaviour and components of exposure and susceptibility to infection, including social ageing and immunosenescence, acquisition of novel parasites and pathogens with age, changes in spatial behaviours, and age-related hygiene and sickness behaviours. Overall, most behavioural changes are expected to result in a reduced exposure rate, but there is relatively little evidence for this phenomenon, emerging largely from a rarity of explicit tests of exposure changes over the lifespan. This review offers a framework for understanding how ageing, behaviour, immunity, and infection interact, providing a series of hypotheses and testable predictions to improve our understanding of health in ageing societies.

Impacts of repeated social defeat on behavior and the brain in a cichlid fish

Social defeat is a powerful experience leading to drastic changes in physiology and behavior, many of which are negative. For example, repeated social defeat in vertebrates results in reduced reproductive success, sickness and behavioral abnormalities that threaten individual survival and species persistence. However, little is known about what neural mechanisms are involved in determining whether an individual is resilient or susceptible to repeated social defeat stress. It also remains unknown whether exclusive use of reactive behaviors after repeated social defeat is maintained over time and impacts future behaviors during subsequent contests. We used a resident-intruder experiment in the African cichlid fish Astatotilapia burtoni to investigate the behavior and neural correlates of these two opposing groups. Behavior was quantified by watching fish during defeat trials and used to distinguish resilient and susceptible individuals. Both resilient and susceptible fish started with searching and freezing behaviors, with searching decreasing and freezing increasing after repeated social defeat. After a 4 day break period, resilient fish used both searching and freezing behaviors during a social defeat encounter with a new resident, while susceptible fish almost exclusively used freezing behaviors. By quantifying neural activation using pS6 in socially relevant brain regions, we identified differential neural activation patterns associated with resilient and susceptible fish and found nuclei that co-varied and may represent functional networks. These data provide the first evidence of specific conserved brain networks underlying social stress resilience and susceptibility in fishes.

The biology of aging in a social world: Insights from free-ranging rhesus macaques

Social adversity can increase the age-associated risk of disease and death, yet the biological mechanisms that link social adversities to aging remain poorly understood. Long-term naturalistic studies of nonhuman animals are crucial for integrating observations of social behavior throughout an individual's life with detailed anatomical, physiological, and molecular measurements. Here, we synthesize the body of research from one such naturalistic study system, Cayo Santiago, which is home to the world's longest continuously monitored free-ranging population of rhesus macaques (Macaca mulatta). We review recent studies of age-related variation in morphology, gene regulation, microbiome composition, and immune function. We also discuss ecological and social modifiers of age-markers in this population. In particular, we summarize how a major natural disaster, Hurricane Maria, affected rhesus macaque physiology and social structure and highlight the context-dependent and domain-specific nature of aging modifiers. Finally, we conclude by providing directions for future study, on Cayo Santiago and elsewhere, that will further our understanding of aging across different domains and how social adversity modifies aging processes.

What Does the MacArthur Scale of Subjective Social Status Measure? Separating Economic Circumstances and Social Status to Predict Health

BACKGROUND

Subjective socioeconomic status is robustly associated with many measures of health and well-being. The MacArthur Scale of Subjective Social Status (i.e., the MacArthur ladder) is the most widely used measure of this construct, but it remains unclear what exactly the MacArthur ladder measures.

PURPOSE

The present research sought to explore the social and economic factors that underlie responses to the MacArthur ladder and its relationship to health.

METHODS

We investigated this issue by examining the relationship between scores on the MacArthur ladder and measures of economic circumstances and noneconomic social status, as well as health and well-being measures, in healthy adults in the USA.

RESULTS

In three studies (total N = 1,310) we found evidence that economic circumstances and social status are distinct constructs that have distinct associations with scores on the MacArthur ladder. We found that both factors exhibit distinct associations with measures of health and well-being and accounted for the association between the MacArthur ladder and each measure of health and well-being.

CONCLUSIONS

Our findings suggest that the MacArthur ladder's robust predictive validity may result from the fact that it measures two factors-economic circumstances and social status-that are each independently associated with health outcomes. These findings provide a novel perspective on the large body of literature that uses the MacArthur ladder and suggests health researchers should do more to disentangle the social and economic aspects of subjective socioeconomic status.

Dopamine Neuron Activity and Stress Signaling as Links Between Social Hierarchy and Psychopathology Vulnerability

BACKGROUND

Social status in humans, generally reflected by socioeconomic status, has been associated, when constrained, with heightened vulnerability to pathologies including psychiatric diseases. Social hierarchy in mice translates into individual and interdependent behavioral strategies of animals within a group. The rules leading to the emergence of a social organization are elusive, and detangling the contribution of social status from other factors, whether environmental or genetic, to normal and pathological behaviors remains challenging.

METHODS

We investigated the mechanisms shaping the emergence of a social hierarchy in isogenic C57BL/6 mice raised in groups of 4 using conditional mutant mouse models and chemogenetic manipulation of dopamine midbrain neuronal activity. We further studied the evolution of behavioral traits and the vulnerability to psychopathological-like phenotypes according to the social status of the animals.

RESULTS

Higher sociability predetermined higher social hierarchy in the colony. Upon hierarchy establishment, higher-ranked mice showed increased anxiety and better cognitive abilities in a working memory task. Strikingly, the higher-ranked mice displayed a reduced activity of dopaminergic neurons within the ventral tegmental area, paired with a decreased behavioral response to cocaine and a decreased vulnerability to depressive-like behaviors following repeated social defeats. The pharmacogenetic inhibition of this neuronal population and the genetic inactivation of glucocorticoid receptor signaling in dopamine-sensing brain areas that resulted in decreased dopaminergic activity promoted accession to higher social ranks.

CONCLUSIONS

Dopamine activity and its modulation by the stress response shapes social organization in mice, potentially linking interindividual and social status differences in vulnerability to psychopathologies.

Hierarchical status is rapidly assessed from behaviourally dominant faces

Recognition of social hierarchy is a key feature that helps us navigate through our complex social environment. Neuroimaging studies have identified brain structures involved in the processing of hierarchical stimuli, but the precise temporal dynamics of brain activity associated with such processing remains largely unknown. In this investigation, we used event-related potentials (ERPs) to examine the effect of social hierarchy on the neural responses elicited by dominant and nondominant faces. Participants played a game where they were led to believe that they were middle-rank players, responding alongside other alleged players, whom they perceived as higher or lower-ranking. ERPs were examined in response to dominant and nondominant faces, and low-resolution electromagnetic tomography (LORETA) was used to identify the implicated brain areas. The results revealed that the amplitude of the N170 component was enhanced for faces of dominant individuals, showing that hierarchy influences the early stages of face processing. A later component, the late positive potential (LPP) appearing between 350-700 ms, also was enhanced for faces of higher-ranking players. Source localisation suggested that the early modulation was due to an enhanced response in limbic regions. These findings provide electrophysiological evidence for enhanced early visual processing of socially dominant faces.

More than a feeling: Effects of competitive asymmetry on human emotions

Competitive interactions have important effects on human emotions. Both victory and defeat can evoke a wide range of emotional reactions, including joy, pride, anger, fear, sadness and shame. However, little is known about what determines this variety of contestants' affective responses. Therefore, the purpose of this study was to evaluate the effects of competitive asymmetry, a common and ecologically relevant feature of animal conflicts, on human emotional responses to winning or losing a contest. To test this hypothesis, we conducted two experiments, the first with high school students (n = 331) and the second with young athletes (n = 73), in which we manipulated the outcomes of successive matches in a non-athletic competition. Thus, by inducing the competitors' scores, ranging from closer to more decisive outcomes, we were able to define the degree of competitive asymmetry in victory and defeat conditions. We then assessed participants' emotional responses to a set of affective stimuli. In the defeat condition, we found in both studies an increase in the occurrence of anger and fear due to more symmetric contests. There were also more frequent reports of shame following more decisive defeats (Experiment 1) and of pride following closer victories (Experiment 2), which were seen neither for sadness nor joy in any of the studies. Supporting our hypothesis, emotional reactions triggered by asymmetries among contestants were consistent with the behavioral patterns commonly seen in symmetric and asymmetric animal conflict, such as dominance/aggressive and defensive/escape behaviors.

Advancing methods for the biodemography of aging within social contexts

Several social dimensions including social integration, status, early-life adversity, and their interactions across the life course can predict health, reproduction, and mortality in humans. Accordingly, the social environment plays a fundamental role in the emergence of phenotypes driving the evolution of aging. Recent work placing human social gradients on a biological continuum with other species provides a useful evolutionary context for aging questions, but there is still a need for a unified evolutionary framework linking health and aging within social contexts. Here, we summarize current challenges to understand the role of the social environment in human life courses. Next, we review recent advances in comparative biodemography and propose a biodemographic perspective to address socially driven health phenotype distributions and their evolutionary consequences using a nonhuman primate population. This new comparative approach uses evolutionary demography to address the joint dynamics of populations, social dimensions, phenotypes, and life history parameters. The long-term goal is to advance our understanding of the link between individual social environments, population-level outcomes, and the evolution of aging.

Stress, associative learning, and decision-making

Exposure to acute and chronic stress has significant effects on the basic mechanisms of associative learning and memory. Stress can both impair and enhance associative learning depending on type, intensity, and persistence of the stressor, the subject's sex, the context that the stress and behavior is experienced in, and the type of associative learning taking place. In some cases, stress can cause or exacerbate the maladaptive behavior that underlies numerous psychiatric conditions including anxiety disorders, obsessive-compulsive disorder, post-traumatic stress disorder, substance use disorder, and others. Therefore, it is critical to understand how the varied effects of stress, which may normally facilitate adaptive behavior, can also become maladaptive and even harmful. In this review, we highlight several findings of associative learning and decision-making processes that are affected by stress in both human and non-human subjects and how they are related to one another. An emerging theme from this work is that stress biases behavior towards less flexible strategies that may reflect a cautious insensitivity to changing contingencies. We consider how this inflexibility has been observed in different associative learning procedures and suggest that a goal for the field should be to clarify how factors such as sex and previous experience influence this inflexibility.

Monitoring the Relationship between Social Network Status and Influenza Based on Social Media Data

BACKGROUND

This article aims to analyze the relationship between user characteristics on social networks and influenza.

METHODS

Three specific research questions are investigated: (1) we classify Weibo updates to recognize influenza-related information based on machine learning algorithms and propose a quantitative model for influenza susceptibility in social networks; (2) we adopt in-degree indicator from complex networks theory as social media status to verify its coefficient correlation with influenza susceptibility; (3) we also apply the LDA topic model to explore users' physical condition from Weibo to further calculate its coefficient correlation with influenza susceptibility. From the perspective of social networking status, we analyze and extract influenza-related information from social media, with many advantages including efficiency, low cost, and real time.

RESULTS

We find a moderate negative correlation between the susceptibility of users to influenza and social network status, while there is a significant positive correlation between physical condition and susceptibility to influenza.

CONCLUSIONS

Our findings reveal the laws behind the phenomenon of online disease transmission, and providing important evidence for analyzing, predicting, and preventing disease transmission. Also, this study provides theoretical and methodological underpinnings for further exploration and measurement of more factors associated with infection control and public health from social networks.

Breaking down silos: the multifaceted nature of obesity and the future of weight management

The continued global increase in the prevalence of obesity prompted a meeting at the Royal Society of London investigating causal mechanisms of the disease, 'Causes of obesity: theories, conjectures, and evidence' in October 2022. Evidence presented indicates areas of obesity science where there have been advancements, including an increased understanding of biological and physiological processes of weight gain and maintenance, yet it is clear there is still debate on the relative contribution of plausible causes of the modern obesity epidemic. Consensus was reached that obesity is not a reflection of diminished willpower, but rather the confluence of multiple, complex factors. As such, addressing obesity requires multifactorial prevention and treatment strategies. The accumulated evidence suggests that a continued focus primarily on individual-level contributors will be suboptimal in promoting weight management at the population level. Here, we consider individual biological and physiological processes within the broader context of sociodemographic and sociocultural exposures as well as environmental changes to optimize research priorities and public health efforts. This requires a consideration of a systems-level approach that efficiently addresses both systemic and group-specific environmental determinants, including psychosocial factors, that often serve as a barrier to otherwise efficacious prevention and treatment options. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Social and early life determinants of survival from cradle to grave: A case study in wild baboons

Field studies of natural mammal populations present powerful opportunities to investigate the determinants of health and aging using fine-grained observations of known individuals across the life course. Here, we synthesize five decades of findings from one such study: the wild baboons of the Amboseli ecosystem in Kenya. First, we discuss the profound associations between early life adversity, adult social conditions, and key aging outcomes in this population, especially survival. Second, we review potential mediators of the relationship between early life adversity and survival in our population. Notably, our tests of two leading candidate mediators-social isolation and glucocorticoid levels-fail to identify a single, strong mediator of early life effects on adult survival. Instead, early adversity, social isolation, and glucocorticoids are independently linked to adult lifespans, suggesting considerable scope for mitigating the negative consequences of early life adversity. Third, we review our work on the evolutionary rationale for early life effects on mortality, which currently argues against clear predictive adaptive responses. Finally, we end by highlighting major themes emerging from the study of sociality, development, and aging in the Amboseli baboons, as well as important open questions for future work.

MHC-B Diversity and Signs of Respiratory Illness in Wild, East African Chimpanzees ( Pan troglodytes schweinfurthii )

Many traits, intrinsic and extrinsic to an organism, contribute to interindividual variation in immunity in wild habitats. The vertebrate Major Histocompatibility Complex (MHC) includes genes encoding antigen-presenting molecules that are highly variable, and that variation often predicts susceptibility/resistance to and recovery from pathogen infection. I compare MHC-B variation at two long-term chimpanzee research sites, Kibale National Park in Uganda and Gombe National Park in Tanzania. Using decades of respiratory health data available for these chimpanzees, I test hypotheses associated with maintenance of diversity at MHC loci, including heterozygote, divergent allele, and rare allele advantage hypotheses, and predictions for unique function of MHC-B in great apes. I found, despite confirmation of recent shared ancestry between Kibale and Gombe chimpanzees, including an overlapping MHC-B allele repertoire and similar MHC-B phenotype compositions, chimpanzees from the two research sites experienced differences in the occurrence of respiratory signs and had different associations of MHC-B diversity with signs of respiratory illness. Kibale chimpanzees with heterozygous genotypes and different peptide-binding supertypes were observed less often with respiratory signs than those homozygous or possessing the same supertypes, but this same association was not observed among Gombe chimpanzees. Gombe chimpanzees with specific MHC-B phenotypes that enable engagement of Natural Killer (NK) cells were observed more often with respiratory signs than chimpanzees with other phenotypes, but this was not observed at Kanyawara. This study emphasizes local adaptation in shaping genetic and phenotypic traits in different infectious disease contexts, even among close genetic relatives of the same subspecies, and highlights utility for continued and simultaneous tracking of host immune genes and specific pathogens in wild species.

Predicting and Moderating COVID-Fear and Stress among College Students in Argentina and the USA

The COVID-19 pandemic negatively affected mental health worldwide and college students were particularly vulnerable to its adverse effects. This longitudinal study was designed to highlight and compare the COVID experiences of college students in Argentina and the USA (N = 361). Specifically, we examined individual factors (gender, emotional regulation, and social support) assessed prior to the pandemic for their role as predictors or moderators of COVID-fear and psychological stress during the first months of the pandemic. The results supported measurement invariance for brief measures of COVID-fear and indicated that, overall, COVID-fear was highest during the second wave of the study (March-April 2020), lowest during the third wave (June 2020), and then rose again during the fourth wave (September 2020). Several interaction effects emerged, revealing important country-level differences in COVID-fear effects for the emotion regulation and social support factors. More so in the Argentina sample than in the USA sample, higher levels of social support at Time 1 were associated with increases in the effect of COVID-fear on stress among students. We discussed the implications of these and other findings for future cross-cultural pandemic-related stress studies.

Exploring the relationship between multiple dimensions of subjective socioeconomic status and self-reported physical and mental health: the mediating role of affect

Introduction

This study aimed to investigate the predictive effects of two types of subjective socioeconomic status on self-reported physical and mental health. Specifically, we examined the MacArthur Scale (MacArthur) which measures perceived socioeconomic rank in the society and a novel scale called ComSim, which assessed how participants compared themselves socioeconomically to others coming from a similar socioeconomic background. We also considered the influence of income, education, and personal relative deprivation (PRD) in these analyses. Additionally, we explored whether these effects were mediated through negative and positive affect.

Methods

The data were collected through a cross-sectional, two-wave survey of 294 women and 294 men, with a mean age 41.6 years. Participants were recruited via an online platform.

Results

The results from multivariate regression models revealed that socioeconomic status measured with both the MacArthur Scale and ComSim significantly predicted both self-reported health measures, whereas income and education did not predict any of these measures in the full multivariate models. PRD only predicted self-reported mental health. Mediation analyses showed that negative and positive affect mediated the relationships between socioeconomic status measured by ComSim and self-reported health measures.

Discussion

These findings are discussed in the context of the similarity hypothesis of social comparison theory. The results underscore the importance of considering multiple dimensions when examining socioeconomic health disparities.

Exogenous oxytocin microinjection into the nucleus accumbens shell attenuates social dominance in group-housed male mice

The nucleus accumbens (NAc), a part of the brain's limbic system, is involved in a variety of brain functions, including reward motivation and social hierarchy. Here, the study investigated the effect of intra-NAc different subregions microinjections of oxytocin on social hierarchy regulation. The hierarchical ranking of group-housed male mice in laboratory settings was determined through the tube test, and a new reliable and robust behavior assay-the mate competition test-was proposed. The mice were randomly divided into two groups, and the bilateral guide cannula was implanted into the shell and core of the NAc, respectively. After social dominance stabilized, changes in social hierarchy were determined through the tube test, warm spot, and mate competition tests. Intra-NAc shell microinjections of oxytocin (0.5 μg/site), but not the core (0.5 μg/site), significantly reduced the social dominance of mice. In addition, oxytocin microinjection into both the shell and core of the NAc significantly increased locomotor ability without affecting anxious behaviors. These findings are tremendously important in understanding the functions of the NAc subregions for social dominance and are more likely to indicate the potential of an oxytocin therapeutic strategy for psychiatric disorders and social impairments.

Antemortem tooth loss as a biomarker of poverty: Dental evidence of "weathering" in a contemporary U.S. skeletal sample

In societies where resources are unequally distributed, structural inequities can be physically embodied over lifetimes. Lived experiences including racism, sexism, classism, and poverty can lead to chronic stress that prematurely ages body systems. This study tests the hypothesis that members of structurally vulnerable groups will exhibit premature aging in the form of antemortem tooth loss (AMTL). Analyzing Black, Indigenous, and People of Color (BIPOC) and white skeletal donors from the University of Tennessee, we predict that individuals from structurally vulnerable groups will exhibit more AMTL than individuals with more social privilege. We find some evidence for increased AMTL in BIPOC individuals, but significantly more AMTL in low-socioeconomic-status white individuals than either BIPOC or high-SES white individuals. We maintain that high rates of AMTL provide evidence of embodied consequences of social policies and utilize the violence continuum to theorize the ways in which poverty and inequity are normalized in U.S. society.

Coping styles vary with species' sociality and life history: A systematic review and meta-regression analysis

Despite a long history of animal studies investigating coping styles, the causal connections between behavior and stress physiology remain unclear. Consistency across taxa in effect sizes would support the idea of a direct causal link maintained by either functional or developmental dependencies. Alternatively, lack of consistency would suggest coping styles are evolutionarily labile. Here, we investigated correlations between personality traits and baseline and stress-induced glucocorticoid levels using a systematic review and meta-analysis. Most personality traits did not consistently vary with either baseline or stress-induced glucocorticoids. Only aggression and sociability showed a consistent negative correlation with baseline glucocorticoids. We found that life history variation affected the relationship between stress-induced glucocorticoid levels and personality traits, especially anxiety and aggression. The relationship between anxiety and baseline glucocorticoids depended on species' sociality with solitary species showing more positive effect sizes. Thus, integration between behavioral and physiological traits depends on species' sociality and life history and suggests high evolutionary lability of coping styles.

Impact of social dominance hierarchy on PACAP expression in the extended amygdala, corticosterone, and behavior in C57BL/6 male mice

The natural alignment of animals into social dominance hierarchies produces adaptive, and potentially maladaptive, changes in the brain that influence health and behavior. Aggressive and submissive behaviors assumed by animals through dominance interactions engage stress-dependent neural and hormonal systems that have been shown to correspond with social rank. Here, we examined the impact of social dominance hierarchies established within cages of group-housed laboratory mice on expression of the stress peptide pituitary adenylate cyclase-activating polypeptide (PACAP) in areas of the extended amygdala comprising the bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). We also quantified the impact of dominance rank on corticosterone (CORT), body weight, and behavior including rotorod and acoustic startle response. Weight-matched male C57BL/6 mice, group-housed (4/cage) starting at 3 weeks of age, were ranked as either most-dominant (Dominant), least-dominant (Submissive) or in-between rank (Intermediate) based on counts of aggressive and submissive encounters assessed at 12 weeks-old following a change in homecage conditions. We found that PACAP expression was significantly higher in the BNST, but not the CeA, of Submissive mice compared to the other two groups. CORT levels were lowest in Submissive mice and appeared to reflect a blunted response following social dominance interactions. Body weight, motor coordination, and acoustic startle were not significantly different between the groups. Together, these data reveal changes in specific neural/neuroendocrine systems that are predominant in animals of lowest social dominance rank, and implicate PACAP in brain adaptations that occur through the development of social dominance hierarchies.

Loss of Social Status and Subjective Well-Being Across the Adult Life Span: Feeling Stuck or Moving Up?

Previous research suggests that loss of social status adversely impacts subjective well-being. Here, we show that important factors modulating this relationship are age differences in beliefs in opportunities and upward mobility. Across two preregistered longitudinal analyses ( N1 = 5,487 and N2 = 1,092; 18–89 years), we found that individuals who hold a stronger belief that they have more opportunities in the future to improve their social status are less likely to suffer from status loss. Further analyses revealed that this interaction effect can be explained by age differences in these beliefs. Specifically, younger individuals were more likely to hold opportunity and upward mobility beliefs and, thus, were better able to maintain their relative level of life satisfaction when experiencing status loss. Overall, these findings contribute to our understanding of how individuals may mitigate the detrimental consequences of status loss to their subjective well-being across the adult life span.

The social environment alters neural responses to a lipopolysaccharide challenge

Sick animals display drastic changes in their behavioral patterns, including decreased activity, decreased food and water intake, and decreased interest in social interactions. These behaviors, collectively called "sickness behaviors", can be socially modulated. For example, when provided with mating opportunities, males of several species show reduced sickness behaviors. While the behavior is known to change, how the social environment affects neural molecular responses to sickness is not known. Here, we used a species, the zebra finch, Taeniopygia guttata, where males have been shown to decrease sickness behaviors when presented with novel females. Using this paradigm, we obtained samples from three brain regions (the hypothalamus, the bed nucleus of the stria terminalis, and the nucleus taeniae) from lipopolysaccharide (LPS) or control treated males housed under four different social environments. Manipulation of the social environment rapidly changed the strength and co-expression patterns of the neural molecular responses to the immune challenge in all brain regions tested, therefore suggesting that the social environment plays a significant role in determining the neural responses to an infection. In particular, brains of males paired with a novel female showed muted immune responses to LPS, as well as altered synaptic signaling. Neural metabolic activity in response to the LPS challenge was also affected by the social environment. Our results provide new insights into the effects of the social environment on brain responses to an infection, thereby improving our understanding of how the social environment can affect health.

Ethical Implications in Making Use of Human Cerebral Organoids for Investigating Stress-Related Mechanisms and Disorders

The generation of three-dimensional cerebral organoids from human-induced pluripotent stem cells (hPSC) has facilitated the investigation of mechanisms underlying several neuropsychiatric disorders, including stress-related disorders, namely major depressive disorder and post-traumatic stress disorder. Generating hPSC-derived neurons, cerebral organoids, and even assembloids (or multi-organoid complexes) can facilitate research into biomarkers for stress susceptibility or resilience and may even bring about advances in personalized medicine and biomarker research for stress-related psychiatric disorders. Nevertheless, cerebral organoid research does not come without its own set of ethical considerations. With increased complexity and resemblance to in vivo conditions, discussions of increased moral status for these models are ongoing, including questions about sentience, consciousness, moral status, donor protection, and chimeras. There are, however, unique ethical considerations that arise and are worth looking into in the context of research into stress and stress-related disorders using cerebral organoids. This paper provides stress research-specific ethical considerations in the context of cerebral organoid generation and use for research purposes. The use of stress research as a case study here can help inform other practices of in vitro studies using brain models with high ethical considerations.

Neural mechanism underlying depressive-like state associated with social status loss

Downward social mobility is a well-known mental risk factor for depression, but its neural mechanism remains elusive. Here, by forcing mice to lose against their subordinates in a non-violent social contest, we lower their social ranks stably and induce depressive-like behaviors. These rank-decline-associated depressive-like behaviors can be reversed by regaining social status. In vivo fiber photometry and single-unit electrophysiological recording show that forced loss, but not natural loss, generates negative reward prediction error (RPE). Through the lateral hypothalamus, the RPE strongly activates the brain's anti-reward center, the lateral habenula (LHb). LHb activation inhibits the medial prefrontal cortex (mPFC) that controls social competitiveness and reinforces retreats in contests. These results reveal the core neural mechanisms mutually promoting social status loss and depressive behaviors. The intertwined neuronal signaling controlling mPFC and LHb activities provides a mechanistic foundation for the crosstalk between social mobility and psychological disorder, unveiling a promising target for intervention.