Primate evidence on the late health effects of early-life adversity

Effects of social environments on male primate HPG and HPA axis developmental programming

Developmental plasticity is particularly important for humans and other primates because of our extended period of growth and maturation, during which our phenotypes adaptively respond to environmental cues. The hypothalamus-pituitary-gonadal (HPG) and hypothalamus-pituitary-adrenal (HPA) axes are likely to be principal targets of developmental "programming" given their roles in coordinating fitness-relevant aspects of the phenotype, including sexual development, adult reproductive and social strategies, and internal responses to the external environment. In social animals, including humans, the social environment is believed to be an important source of cues to which these axes may adaptively respond. The effects of early social environments on the HPA axis have been widely studied in humans, and to some extent, in other primates, but there are still major gaps in knowledge specifically relating to males. There has also been relatively little research examining the role that social environments play in developmental programming of the HPG axis or the HPA/HPG interface, and what does exist disproportionately focuses on females. These topics are likely understudied in males in part due to the difficulty of identifying developmental milestones in males relative to females and the general quiescence of the HPG axis prior to maturation. However, there are clear indicators that early life social environments matter for both sexes. In this review, we examine what is known about the impact of social environments on HPG and HPA axis programming during male development in humans and nonhuman primates, including the role that epigenetic mechanisms may play in this programming. We conclude by highlighting important next steps in this research area.

DNA methylation signatures of early-life adversity are exposure-dependent in wild baboons

The early-life environment can profoundly shape the trajectory of an animal's life, even years or decades later. One mechanism proposed to contribute to these early-life effects is DNA methylation. However, the frequency and functional importance of DNA methylation in shaping early-life effects on adult outcomes is poorly understood, especially in natural populations. Here, we integrate prospectively collected data on fitness-associated variation in the early environment with DNA methylation estimates at 477,270 CpG sites in 256 wild baboons. We find highly heterogeneous relationships between the early-life environment and DNA methylation in adulthood: aspects of the environment linked to resource limitation (e.g., low-quality habitat, early-life drought) are associated with many more CpG sites than other types of environmental stressors (e.g., low maternal social status). Sites associated with early resource limitation are enriched in gene bodies and putative enhancers, suggesting they are functionally relevant. Indeed, by deploying a baboon-specific, massively parallel reporter assay, we show that a subset of windows containing these sites are capable of regulatory activity, and that, for 88% of early drought-associated sites in these regulatory windows, enhancer activity is DNA methylation-dependent. Together, our results support the idea that DNA methylation patterns contain a persistent signature of the early-life environment. However, they also indicate that not all environmental exposures leave an equivalent mark and suggest that socioenvironmental variation at the time of sampling is more likely to be functionally important. Thus, multiple mechanisms must converge to explain early-life effects on fitness-related traits.

Survival rates and mortality risks of Plecturocebus cupreus at the California National Primate Research Center

This article describes survivorship and explores factors affecting mortality risks in a captive colony of coppery titi monkeys (Plecturocebus cupreus) housed at the California National Primate Research Center (CNPRC), at UC Davis, in Davis, CA. We analyzed data collected on individuals since the colony's creation in the 1960s, with a sample of 600 animals with partially complete information (date of birth, age at death, body mass, parental lineage). We used three methods: (1) Kaplan-Meier regressions followed by a log-rank test to compare survival in male and female titi monkeys, (2) a breakpoint analysis to identify shifts in the survival curves, and (3) Cox regressions to test the effect of body mass change, parental pair tenure, and parental age on mortality risk. We found that males tend to have a longer median lifespan than females (14.9 and 11.4 years; p = 0.094) and that survival decreases earlier in males than in females during adulthood (9.8 and 16.2 years). A body mass loss of 10% from adulthood to the time of death led to a 26% higher risk of dying (p < 0.001) as compared to an individual with stable body mass. We found no evidence of sociobiological factors on mortality risks (parental age, parental pair tenure), but an exploratory analysis suggested that a higher rate of offspring conceptions increases mortality risks. This description of factors influencing survival and mortality in titi monkeys is a first step toward understanding aging in this species to consider titi monkeys as a primate model for socioemotional aging.

Early life adversities and lifelong health outcomes: A review of the literature on large, social, long-lived nonhuman mammals

Social nonhuman animals are powerful models for studying underlying factors related to lifelong health outcomes following early life adversities (ELAs). ELAs can be linked to lifelong health outcomes depending on the species, system, sensitive developmental periods, and biological pathways. This review focuses on the literature surrounding ELAs and lifelong health outcomes in large, social, relatively long-lived nonhuman mammals including nonhuman primates, canids, hyenas, elephants, ungulates, and cetaceans. These mammals, like humans but unlike the most-studied rodent models, have longer life histories, complex social structures, larger brains, and comparable stress and reproductive physiology. Collectively, these features make them compelling models for comparative aging research. We review studies of caregiver, social, and ecological ELAs, often in tandem, in these mammals. We consider experimental and observational studies and what each has contributed to our knowledge of health across the lifespan. We demonstrate the continued and expanded need for comparative research to inform about the social determinants of health and aging in both humans and nonhuman animals.

DNA methylation signatures of early life adversity are exposure-dependent in wild baboons

The early life environment can profoundly shape the trajectory of an animal's life, even years or decades later. One mechanism proposed to contribute to these early life effects is DNA methylation. However, the frequency and functional importance of DNA methylation in shaping early life effects on adult outcomes is poorly understood, especially in natural populations. Here, we integrate prospectively collected data on fitness-associated variation in the early environment with DNA methylation estimates at 477,270 CpG sites in 256 wild baboons. We find highly heterogeneous relationships between the early life environment and DNA methylation in adulthood: aspects of the environment linked to resource limitation (e.g., low-quality habitat, early life drought) are associated with many more CpG sites than other types of environmental stressors (e.g., low maternal social status). Sites associated with early resource limitation are enriched in gene bodies and putative enhancers, suggesting they are functionally relevant. Indeed, by deploying a baboon-specific, massively parallel reporter assay, we show that a subset of windows containing these sites are capable of regulatory activity, and that, for 88% of early drought-associated sites in these regulatory windows, enhancer activity is DNA methylation-dependent. Together, our results support the idea that DNA methylation patterns contain a persistent signature of the early life environment. However, they also indicate that not all environmental exposures leave an equivalent mark and suggest that socioenvironmental variation at the time of sampling is more likely to be functionally important. Thus, multiple mechanisms must converge to explain early life effects on fitness-related traits.

Social isolation and the brain: effects and mechanisms

An obvious consequence of the coronavirus disease (COVID-19) pandemic is the worldwide reduction in social interaction, which is associated with many adverse effects on health in humans from babies to adults. Although social development under normal or isolated environments has been studied since the 1940s, the mechanism underlying social isolation (SI)-induced brain dysfunction remains poorly understood, possibly due to the complexity of SI in humans and translational gaps in findings from animal models. Herein, we present a systematic review that focused on brain changes at the molecular, cellular, structural and functional levels induced by SI at different ages and in different animal models. SI studies in humans and animal models revealed common socioemotional and cognitive deficits caused by SI in early life and an increased occurrence of depression and anxiety induced by SI during later stages of life. Altered neurotransmission and neural circuitry as well as abnormal development and function of glial cells in specific brain regions may contribute to the abnormal emotions and behaviors induced by SI. We highlight distinct alterations in oligodendrocyte progenitor cell differentiation and oligodendrocyte maturation caused by SI in early life and later stages of life, respectively, which may affect neural circuit formation and function and result in diverse brain dysfunctions. To further bridge animal and human SI studies, we propose alternative animal models with brain structures and complex social behaviors similar to those of humans.

Nonhuman primate abnormal behavior: Etiology, assessment, and treatment

Across captive settings, nonhuman primates may develop an array of abnormal behaviors including stereotypic and self-injurious behavior. Abnormal behavior can indicate a state of poor welfare, since it is often associated with a suboptimal environment. However, this may not always be the case as some behaviors can develop independently of any psychological distress, be triggered in environments known to promote welfare, and be part of an animal's coping mechanism. Furthermore, not all animals develop abnormal behavior, which has led researchers to assess risk factors that differentiate individuals in the display of these behaviors. Intrinsic risk factors that have been identified include the animal's species and genetics, age, sex, temperament, and clinical condition, while environmental risk factors include variables such as the animal's rearing, housing condition, husbandry procedures, and research experiences. To identify specific triggers and at-risk animals, the expression of abnormal behavior in captive nonhuman primates should be routinely addressed in a consistent manner by appropriately trained staff. Which behaviors to assess, what assessment methods to use, which primates to monitor, and the aims of data collection should all be identified before proceeding to an intervention and/or treatment. This article provides guidance for this process, by presenting an overview of known triggers and risk factors that should be considered, steps to design a comprehensive evaluation plan, and strategies that might be used for prevention or treatment. It also outlines the tools and processes for assessing and evaluating behavior in an appendix. This process will lead to a better understanding of abnormal behavior in captive primate colonies and ultimately to improved welfare.

Learning Ability and Hippocampal Transcriptome Responses to Early and Later Life Environmental Complexities in Dual-Purpose Chicks

In this study, we hypothesized that complex early-life environments enhance the learning ability and the hippocampal plasticity when the individual is faced with future life challenges. Chicks were divided into a barren environment group (BG), a litter materials group (LG), and a perches and litter materials group (PLG) until 31 days of age, and then their learning abilities were tested following further rearing in barren environments for 22 days. In response to the future life challenge, the learning ability showed no differences among the three groups. In the hippocampal KEGG pathways, the LG chicks showed the downregulation of neural-related genes neuronal growth regulator 1 (NEGR1) and neurexins (NRXN1) in the cell adhesion molecules pathway compared to the BG (p < 0.05). Immune-related genes TLR2 in Malaria and Legionellosis and IL-18 and IL18R1 in the TNF signaling pathway were upregulated in the LG compared to in the BG (p < 0.05). Compared to the BG, the PLG displayed upregulated TLR2A in Malaria (p < 0.05). The PLG showed upregulated neural-related gene, i.e., neuronal acetylcholine receptor subunit alpha-7-like (CHRNA8) in the nicotine addiction pathway and secretagogin (SCGN) gene expression, as compared to the LG (p < 0.05). In conclusion, early-life environmental complexities had limited effects on the learning ability in response to a future life challenge. Early-life perches and litter materials can improve neural- and immune-related gene expression and functional pathways in the hippocampus of chicks.

Social ageing: exploring the drivers of late-life changes in social behaviour in mammals

Social interactions help group-living organisms cope with socio-environmental challenges and are central to survival and reproductive success. Recent research has shown that social behaviour and relationships can change across the lifespan, a phenomenon referred to as 'social ageing'. Given the importance of social integration for health and well-being, age-dependent changes in social behaviour can modulate how fitness changes with age and may be an important source of unexplained variation in individual patterns of senescence. However, integrating social behaviour into ageing research requires a deeper understanding of the causes and consequences of age-based changes in social behaviour. Here, we provide an overview of the drivers of late-life changes in sociality. We suggest that explanations for social ageing can be categorized into three groups: changes in sociality that (a) occur as a result of senescence; (b) result from adaptations to ameliorate the negative effects of senescence; and/or (c) result from positive effects of age and demographic changes. Quantifying the relative contribution of these processes to late-life changes in sociality will allow us to move towards a more holistic understanding of how and why these patterns emerge and will provide important insights into the potential for social ageing to delay or accelerate other patterns of senescence.

Childhood Emotional Neglect and Cardiovascular Disease: A Narrative Review

Psychosocial factors predict the incidence and progression of cardiovascular disease (CVD). There is accumulating evidence for the importance of childhood maltreatment for the development and progression of both CVD-related risk factors and CVD. However, past research has predominantly focused on active forms of childhood maltreatment such as emotional abuse, physical abuse, and sexual abuse. At the same time, childhood neglect as a relatively silent form of childhood maltreatment received less attention. Childhood emotional neglect is the most common form of neglect. This narrative review summarizes findings on the association between childhood emotional neglect and CVD and potential underlying mechanisms. These mechanisms may involve biological factors (i.e., elevated inflammation, autonomic dysregulation, dysregulated HPA axis, and altered brain development), psychological variables and mental health (i.e., depression and anxiety), and health behaviors (i.e., eating behavior, smoking, drug use, physical activity) and interpersonal aspects. Evidence suggests that emotional neglect is associated with CVD and CVD risk factors such as obesity, diabetes, inflammation, a dysregulated stress system, altered brain development, depression and other psychological abnormalities (i.e., emotion-regulation difficulties), interpersonal difficulties, and lack of health behaviors. Specific subtypes of childhood maltreatment may be associated with CVD via different mechanisms. This review further encompasses clinical suggestions, identifies research gaps, and has implications for future studies. However, more research with better study designs is desperately needed to identify the exact underlying mechanisms and opportunities for mitigating the negative health consequences of emotional neglect to reduce the prevalence and progression of CVD.

Parentally deprived juvenile Owl monkeys suffer from long-term high infection rates but not from altered hair cortisol concentrations nor from stereotypic behaviours

BACKGROUND

In captive colonies, owl monkeys' mothers sometimes reject their newborns. To prevent, mortality infants are manually raised by veterinarians. Both parental separation and rejection are stressful experiences, associated with elevated stress, physical, and behavioural disorders. The effect of parental deprivation in IVITA's owl monkeys stress profiles and health is unknown.

METHODS

We compared stress biomarkers such as hair cortisol (using cortisol ELISA), stereotypic behaviours (with infrared cameras), and infection histories in juveniles separated from parents soon after birth (n = 14, ~17 months) and controls (n = 11, ~17 months).

RESULTS

Parentally deprived owl monkeys show higher infection rates than controls (p = .001). However, they display no higher incidence of biomarkers of stress: Neither stereotypic behaviour nor cortisol in hair was different between cohorts. Irrespective of deprivation status, rates of infection, and concentration of cortisol in hair were positively associated (R² = .29, p = .005).

CONCLUSION

Early parental deprivation and natural high levels of cortisol secretion are associated with elevated infection levels in the IVITA owl monkey juveniles detectable up to 17 months post separation.

Oxytocin promotes prosocial behavior and related neural responses in infant macaques at-risk for compromised social development

Although positive effects of oxytocin (OT) on social functioning are well-demonstrated, little is known about the mechanisms through which OT may drive early social development, or its therapeutic efficacy in infancy. To address these critical issues, we investigated the effects of exogenous OT on neural (EEG) and behavioral responses during observation of live facial gestures in infant macaques with limited social exposure (i.e. nursery-reared). Three key findings were revealed. First, OT increased alpha suppression over posterior scalp regions during observation of facial gestures but not non-biological movement, suggesting that OT targets self-other matching and attentional cortical networks involved in social perception from very early infancy. Second, OT increased infant production of matching facial gestures and attention towards the most socially-relevant facial stimuli, both behaviors typically silenced by early social deprivation. Third, infants with higher cortisol levels appeared to benefit the most from OT, displaying greater improvements in prosocial behaviors after OT administration. Altogether, these findings suggest that OT promotes prosocial behaviors and associated neural responses likely impacted by early social adversity, and demonstrate the potential of OT administration to ameliorate social difficulties in the context of neurodevelopmental and early-emerging psychiatric disorders, at a developmental stage when brain plasticity is greatest.

Identifying animal complex cognition requires natural complexity

The search for human cognitive uniqueness often relied on low ecological tests with subjects experiencing unnatural ontogeny. Recently, neuroscience demonstrated the significance of a rich environment on the development of brain structures and cognitive abilities. This stresses the importance to consider the prior knowledge that subjects bring in any experiment. Second, recent developments in multivariate statistics control precisely for a number of factors and their interactions. Making controls in natural observations equivalent and sometimes superior to captive experimental studies without the drawbacks of the latter methods. Thus, we can now investigate complex cognition by accounting for many different factors, as required when solving tasks in nature. Combining both progresses allows us to move toward an “experience-specific cognition”, recognizing that cognition varies extensively in nature as individuals adapt to the precise challenges they experience in life. Such cognitive specialization makes cross-species comparisons more complex, while potentially identifying human cognitive uniqueness.

Neutrophil to Lymphocyte Ratio (NLR) in captive chimpanzees (Pan troglodytes): The effects of sex, age, and rearing

In humans, neutrophil to lymphocyte ratio (NLR) has been used as a clinical tool in diagnosis and/or prognosis of a variety of cancers and medical conditions, as well as in measuring physiological stress over time. Given the close phylogenetic relationship and physical similarities between humans and apes, NLR may similarly be a useful diagnostic tool in assessing chimpanzee health. Only one study has examined NLR in apes, reporting that NLR increased with age and was affected by body-mass index and sex. In the current study, we examined changes in NLR data from longitudinal health records for 443 chimpanzees in two captive chimpanzee populations. Using these data, we analyzed intra-individual changes and inter-individual differences in NLR as a function of age, rearing history, and sex. Contrary to previous studies in humans and the one previous study in chimpanzees, NLR values did not change over a 10-year timespan within individual chimpanzees. However, cross-sectional comparisons revealed a significant quadratic relationship between age and NLR, with the highest values during mid-life (20-30 years of age) and the lowest values in younger and older individuals. Additionally, males and mother-reared individuals had higher NLR than females and nursery-reared chimpanzees, respectively. Lastly, males and those with higher NLR values died at younger ages. These findings suggest that NLR may be useful as a predictor of longevity in chimpanzees. However, given the complexities of these relationships, more research is needed to determine the utility of NLR as a diagnostic health tool for chimpanzees.

Social bonds do not mediate the relationship between early adversity and adult glucocorticoids in wild baboons

In humans and other animals, harsh conditions in early life can have profound effects on adult physiology, including the stress response. This relationship may be mediated by a lack of supportive relationships in adulthood. That is, early life adversity may inhibit the formation of supportive social ties, and weak social support is itself often linked to dysregulated stress responses. Here, we use prospective, longitudinal data from wild baboons in Kenya to test the links between early adversity, adult social bonds, and adult fecal glucocorticoid hormone concentrations (a measure of hypothalamic-pituitary-adrenal [HPA] axis activation and the stress response). Using a causal inference framework, we found that experiencing one or more sources of early adversity led to a 9 to 14% increase in females' glucocorticoid concentrations across adulthood. However, these effects were not mediated by weak social bonds: The direct effects of early adversity on adult glucocorticoid concentrations were 11 times stronger than the effects mediated by social bonds. This pattern occurred, in part, because the effect of social bonds on glucocorticoids was weak compared to the powerful effects of early adversity on glucocorticoid levels in adulthood. Hence, in female baboons, weak social bonds in adulthood are not enough to explain the effects of early adversity on glucocorticoid concentrations. Together, our results support the well-established notions that early adversity and weak social bonds both predict poor adult health. However, the magnitudes of these two effects differ considerably, and they may act independently of one another.

Does early peer relationship last long? The enduring influence of early peer relationship on depression in middle and later life

BACKGROUND

Previous studies focus on the health effect of early family relationship rather than early peer relationship. Thus, this study aimed to examine the causal effect of early peer relationship on depression in middle and later life.

METHODS

Based on the China Health and Retirement Longitudinal Study data 2013-2014 (N = 15,343), this study used the propensity score matching approach to estimate the causal effect of early peer relationship, including establishment (whether having good friends in childhood), engagement (frequency of playing with friends in childhood) and feeling (feeling of loneliness in childhood), on depression in middle and later life, as well as the educational heterogeneity of this health effect.

RESULTS

Elevated feeling of loneliness and reduced engagement of early peer relationship were causally related to elevated depression in middle and later life, but having good friends in childhood was not related to later life depression. For individuals with more education, less feeling of loneliness in childhood had a stronger effect on reduced depression in middle and later life, but more engagement in childhood peer relationship only had a weaker effect on reduced depression in middle and later life.

LIMITATIONS

A retrospective survey and single-item measures of early peer relationship were used, the intermediate link across the life course and potential neurobiological mechanisms were also not empirically examined.

CONCLUSIONS

We should focus more on the engagement and quality of early peer relationship, as well as the balance between education and socializing in childhood, to prevent from the detrimental health effect of early peer relationship disadvantage.

Early-life relationships matter: Social position during early life predicts fitness among female spotted hyenas

How social development in early-life affects fitness remains poorly understood. Though there is growing evidence that early-life relationships can affect fitness, little research has investigated how social positions develop or whether there are particularly important periods for social position development in an animal's life history. In long-lived species in particular, understanding the lasting consequences of early-life social environments requires detailed, long-term datasets. Here we used a 25-year dataset to test whether social positions held during early development predicted adult fitness. Specifically, we quantified social position using three social network metrics: degree, strength and betweenness. We determined the social position of each individual in three types of networks during each of three stages of ontogeny to test whether they predict annual reproductive success (ARS) or longevity among adult female spotted hyenas Crocuta crocuta. The social positions occupied by juvenile hyenas did predict their fitness, but the effects of social position on fitness measures differed between stages of early development. Network metrics when individuals were young adults better predicted ARS, but network metrics for younger animals, particularly when youngsters were confined to the communal den, better predicted longevity than did metrics assessed during other stages of development. Our study shows how multiple types of social bonds formed during multiple stages of social development predict lifetime fitness outcomes. We suggest that social bonds formed during specific phases of development may be more important than others when considering fitness outcomes.

Early-life infection with a bacterial pathogen increases expression levels of innate immunity related genes during adulthood in zebrafish

Early-life exposure to different stressors can lead to various consequences on fish health status in later life development. To evaluate the effects of Aeromonas salmonicida achromogenes infection in the early-life on immunity in adulthood, zebrafish were either early-infected at 18 days post-fertilization (dpf), chronically infected from 18 to 35 dpf, or late infected at 35 dpf and then grown up to 61 dpf to be re-infected with the pathogen. The age of first infection was shown to influence both, level and timing of the immune gene expressions, especially for inflammation-related genes. In addition, evidence for an innate immune memory in zebrafish primarily infected with the pathogen at 35 dpf and re-infected at 61dpf provide new insights to consolidate the concept of a "trained" innate immunity in fish.

Social determinants of health and survival in humans and other animals

The social environment, both in early life and adulthood, is one of the strongest predictors of morbidity and mortality risk in humans. Evidence from long-term studies of other social mammals indicates that this relationship is similar across many species. In addition, experimental studies show that social interactions can causally alter animal physiology, disease risk, and life span itself. These findings highlight the importance of the social environment to health and mortality as well as Darwinian fitness-outcomes of interest to social scientists and biologists alike. They thus emphasize the utility of cross-species analysis for understanding the predictors of, and mechanisms underlying, social gradients in health.

Population-based RNA profiling in Add Health finds social disparities in inflammatory and antiviral gene regulation to emerge by young adulthood

Health in later life varies significantly by individual demographic characteristics such as age, sex, and race/ethnicity, as well as by social factors including socioeconomic status and geographic region. This study examined whether sociodemographic variations in the immune and inflammatory molecular underpinnings of chronic disease might emerge decades earlier in young adulthood. Using data from 1,069 young adults from the National Longitudinal Study of Adolescent to Adult Health (Add Health)-the largest nationally representative and ethnically diverse sample with peripheral blood transcriptome profiles-we analyzed variation in the expression of genes involved in inflammation and type I interferon (IFN) response as a function of individual demographic factors, sociodemographic conditions, and biobehavioral factors (smoking, drinking, and body mass index). Differential gene expression was most pronounced by sex, race/ethnicity, and body mass index (BMI), but transcriptome correlates were identified for every demographic dimension analyzed. Inflammation-related gene expression showed the most pronounced variation as a function of biobehavioral factors (BMI and smoking) whereas type I IFN-related transcripts varied most strongly as a function of individual demographic characteristics (sex and race/ethnicity). Bioinformatic analyses of transcription factor and immune-cell activation based on transcriptome-wide empirical differences identified additional effects of family poverty and geographic region. These results identify pervasive sociodemographic differences in immune-cell gene regulation that emerge by young adulthood and may help explain social disparities in the development of chronic illness and premature mortality at older ages.

Population-based RNA profiling in Add Health finds social disparities in inflammatory and antiviral gene regulation to emerge by young adulthood

Health in later life varies significantly by individual demographic characteristics such as age, sex, and race/ethnicity, as well as by social factors including socioeconomic status and geographic region. This study examined whether sociodemographic variations in the immune and inflammatory molecular underpinnings of chronic disease might emerge decades earlier in young adulthood. Using data from 1,069 young adults from the National Longitudinal Study of Adolescent to Adult Health (Add Health)-the largest nationally representative and ethnically diverse sample with peripheral blood transcriptome profiles-we analyzed variation in the expression of genes involved in inflammation and type I interferon (IFN) response as a function of individual demographic factors, sociodemographic conditions, and biobehavioral factors (smoking, drinking, and body mass index). Differential gene expression was most pronounced by sex, race/ethnicity, and body mass index (BMI), but transcriptome correlates were identified for every demographic dimension analyzed. Inflammation-related gene expression showed the most pronounced variation as a function of biobehavioral factors (BMI and smoking) whereas type I IFN-related transcripts varied most strongly as a function of individual demographic characteristics (sex and race/ethnicity). Bioinformatic analyses of transcription factor and immune-cell activation based on transcriptome-wide empirical differences identified additional effects of family poverty and geographic region. These results identify pervasive sociodemographic differences in immune-cell gene regulation that emerge by young adulthood and may help explain social disparities in the development of chronic illness and premature mortality at older ages.

Rearing condition may alter neonatal development of captive Bolivian squirrel monkeys (Saimiri boliviensis boliviensis)

Nursery rearing has well-known consequences for primate species. Relative to some other primate species, research has indicated a reduced impact of nursery rearing on squirrel monkeys, particularly in terms of rates, severity, and persistence of abnormal behavior. We administered the Primate Neonatal Neurobehavioral Assessment to 29 dam-reared and 13 nursery-reared squirrel monkeys (Saimiri boliviensis boliviensis) at 2 and 6 weeks of age. Mixed-model ANOVAs comparing composite scores and individual assessment items across age, rearing status, and sex revealed a number of developmental differences. Dam-reared infants scored higher on all four composite measures compared to nursery-reared infants (p < .05) indicating that nursery-reared animals had slower motor development, were less active and attentive, and were more passive than their dam-reared counterparts. Consistent with infant rhesus macaques, nursery-reared squirrel monkeys showed an increased sensitivity to tactile stimulation (p < .05). Altogether, these results suggest a disruption of species-typical development when squirrel monkey infants are reared in a nursery setting, with activity, orientation, and state control areas most affected, though experimental research is needed to determine if this is a causal relationship. Contrary to previous behavioral research, there are likely developmental differences between dam-reared infant squirrel monkeys and those reared in a nursery setting.

Early life experience and alterations of group composition shape the social grooming networks of former pet and entertainment chimpanzees (Pan troglodytes)

The long-term effects of early life adversities on social capacities have been documented in humans and wild-caught former laboratory chimpanzees (Pan troglodytes). However, former pet and entertainment chimpanzees have received little attention to date. This study aimed to investigate the long-term effects of early life experience on 18 former pet and entertainment chimpanzees, based on social grooming data collected at a primate rescue centre over a 12-year period. Moreover, we also focused on the possible short-term effects that alterations to group composition might have on grooming patterns. For this purpose, we compared stable and unstable periods (i.e. where alterations to group composition occurred). We used two individual social network measures to analyse the grooming activity and the distribution of grooming among group mates for each individual. We could show that wild-caught chimpanzees were significantly more selective regarding their grooming partners and spent less time grooming when compared to their captive born companions. We also found that individuals who were predominantly housed without conspecifics during infancy spent less time grooming compared to those who were predominantly housed with conspecifics during infancy. Furthermore, we found that alterations to the group composition had short-term effects on the distribution of social grooming from a more equal distribution during periods with a stable group composition towards a more unequal and selective distribution during unstable periods. Thus, we conclude that the social grooming networks of former pet and entertainment chimpanzees are shaped not only by long-term effects such as early life experience, but also by short-term effects such as alterations to group composition. Remarkably, we found not only captive born chimpanzees but also wild-caught individuals to adjust their grooming to socially challenging situations by modifying their grooming distribution in a similar way.

Bridging the species gap in translational research for neurodevelopmental disorders

The prevalence and societal impact of neurodevelopmental disorders (NDDs) continue to increase despite years of research in both patient populations and animal models. There remains an urgent need for translational efforts between clinical and preclinical research to (i) identify and evaluate putative causes of NDD, (ii) determine their underlying neurobiological mechanisms, (iii) develop and test novel therapeutic approaches, and (iv) translate basic research into safe and effective clinical practices. Given the complexity behind potential causes and behaviors affected by NDDs, modeling these uniquely human brain disorders in animals will require that we capitalize on unique advantages of a diverse array of species. While much NDD research has been conducted in more traditional animal models such as the mouse, ultimately, we may benefit from creating animal models with species that have a more sophisticated social behavior repertoire such as the rat (Rattus norvegicus) or species that more closely related to humans, such as the rhesus macaque (Macaca mulatta). Here, we highlight the rat and rhesus macaque models for their role in previous psychological research discoveries, current efforts to understand the neurobiology of NDDs, and focus on the convergence of behavior outcome measures that parallel features of human NDDs.

The current state of animal models in research: A review

Animal models have provided invaluable information in the pursuit of medical knowledge and alleviation of human suffering. The foundations of our basic understanding of disease pathophysiology and human anatomy can largely be attributed to preclinical investigations using various animal models. Recently, however, the scientific community, citing concerns about animal welfare as well as the validity and applicability of outcomes, has called the use of animals in research into question. In this review, we seek to summarize the current state of the use of animal models in research.

Unravelling the nature of early (autobiographical) memory

In this article, I provide an overview of the problems associated with understanding the nature of early autobiographical memory and discuss issues concerning the forgetting of these memories (infantile/childhood amnesia). Specifically, I provide a brief exegesis as to whether such memories are stored in a fragile manner to begin with, become difficult to retrieve over time, or both. In order to answer this and other related questions, I review the contribution of the articles in this special issue to understanding the enigma that is infantile/childhood amnesia. I then outline some of the issues that remain and suggest a functional approach to understanding why the forgetting of early experiences may be more adaptive than remembering them. I conclude by suggesting that infantile amnesia may actually begin during infancy itself.

Midlife reversibility of early-established biobehavioral risk factors: A research agenda

Epidemiological evidence links exposure to early life adversities-such as childhood maltreatment-with impaired health and well-being in adulthood. Since these effects are usually unrecognized or untreated in childhood, preventive and remediating interventions in adults are needed. Our focus on adulthood prompted three major questions. First, does our increased understanding of mechanisms accounting for the long-term effects of early life adversities help delineate underlying dimensions that underscore key similarities and differences among these adversities? Second, can adults accurately report on adversities they experienced in childhood? Third, can we identify malleable risk processes in adulthood that might be targets for preventive intervention? Supported by the National Institute on Aging, the U.K. Economic and Social and the Biotechnology and Biological Sciences Research Councils, a network of researchers in human and animal development addressed these questions through meetings and literature review. A small number of dimensions may adequately distinguish among a range of co-occurring childhood adversities. Widely used adult ascertainments of childhood adversity are poorly related to prospective ascertainment. Strategies for preventive interventions should be aimed both at adults who were actually exposed to adversity as well as those who recall adversity, but the targeted risk processes may be different. Now is an opportune time to support research on adult interventions based on unfolding research on critical periods of sensitivity to adversity in fetal and child development, on improved understanding of risk mechanisms that may persist across the life span, and on new insights on enhancing neuroplasticity in adults. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Links between traumatic experiences in childhood or early adulthood and lifetime binge eating disorder

OBJECTIVES

To evaluate the association between childhood or early adulthood traumatic experiences and adulthood binge eating disorder (BED) in 326 male and 1158 female patients. A structured clinical interview for the DSM-IV (SCID-I/P)-adapted to lifetime exploration for the diagnosis of BED and for DSM-IV Childhood Disorders was conducted by the psychiatrist.

RESULTS

Emotional neglect was the most frequent event experienced (77.8% of females vs. 63.5% of males, p < 0.0001), ahead of physical abuse (23.3%), witnessed domestic violence (17.7%) and sexual abuse (11.8% of females vs. 2.8% of males (p < 0.0001)). The prevalence rate for BED in the whole population was 34.9%. The independent predictors for BED were emotional neglect in male obese patients (OR = 3.49; IC95% (1.94-6.29); p < 0.0001) and physical abuse (OR = 1.56; IC95% (1.14-2.12); p = 0.0047), emotional neglect (OR = 1.83; IC95% (1.37-2.44); p < 0.0001), and sexual abuse (OR = 1.80; IC95% (1.22-2.65); p = 0.0029) in female patients. With a cut-off value of 17, the sensitivity of the Binge Eating Scale for BED during lifetime was 50.8% with 74.7% specificity.

CONCLUSIONS

This study shows that early psychological events are independent predictors of BED in obese female and male adults. The BES questionnaire is a poor predictor of BED during lifetime and a structured clinical interview should be recommended.

Early Social Stress Promotes Inflammation and Disease Risk in Rhesus Monkeys

Early social stress has potent lifelong health effects. We examined the association of early stress in the attachment relationship (low maternal sensitivity, low MS), lower maternal social hierarchy rank, and greater frequency of group-level social conflict, with biomarkers of inflammatory stress response in plasma (IL-8, MCP-1 and CRP collected two hours after temporary separation from mothers and social groups) and risk for developing a common macaques disease outcome (infectious colitis) in 170 socially-housed rhesus monkeys. We controlled for gene-environment correlations by comparing cross-fostered subjects with infants reared by their biological mothers. Low MS predicted higher levels of pro-inflammatory cytokines and proteins at 3-4 months of age (F(3, 162) = 3.508, p = 0.002, partial eta2 = 0.061) and higher lifetime risk for developing colitis for up to twelve years of age (chi square = 5.919, p = 0.026). Lower maternal social rank (F (3, 162) = 3.789, p = 0.012, partial eta2 = 0.06) and higher rates of social conflict (F (3, 162) = 4.264, p = 0.006, partial eta2 = 0.074) each also predicted greater inflammation in infancy, but not lifetime colitis risk (both p > 0.05). The effects of low MS, lower social rank, and higher social conflict were significant in infants reared by biological mothers and cross-fostered infants, suggesting that our results did not arise from gene-environment correlations, but environmental stressors alone. We conclude that several types of early social stress confer risk for inflammation in infancy, but that stress in the mother-infant relationship may confer the longest-term risk for adverse health outcomes.

Early psychosocial deprivation and adolescent risk-taking: The role of motivation and executive control

Risk-taking in adolescence has been often associated with early life adversities. However, the impact of such macrolevel factors on risk behavior has been rarely studied in humans. To address these gaps we recruited a sample of young adolescents who were part of a randomized control trial of foster care. Children institutionalized at or soon after birth were randomly assigned either to be removed from institutions and placed into a family or foster care intervention or to remain in institutions receiving care as usual. These children were subsequently followed up through 12 years of age and compared with a sample of children who had never been institutionalized. Using this sample, we examined the impact of early childhood deprivation on risk-taking behavior and explored the role of motivation (i.e., sensation seeking) and executive control (i.e., planning). Early psychosocial deprivation decreased engagement in risk-taking among young adolescents by reducing sensation seeking, a motivation often associated with risk-taking in adolescence. The impact of early psychosocial deprivation on sensation seeking and consequently on engagement in risk-taking was further reduced by its deleterious effects on executive control. These findings challenge the traditional view according to which risk behavior is a maladaptive response to adversities and suggest that it may represent adolescents' attempts to fulfill important motivations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Neurocognitive Development of Motivated Behavior: Dynamic Changes across Childhood and Adolescence

The ability to anticipate and respond appropriately to the challenges and opportunities present in our environments is critical for adaptive behavior. Recent methodological innovations have led to substantial advances in our understanding of the neurocircuitry supporting such motivated behavior in adulthood. However, the neural circuits and cognitive processes that enable threat- and reward-motivated behavior undergo substantive changes over the course of development, and these changes are less well understood. In this article, we highlight recent research in human and animal models demonstrating how developmental changes in prefrontal-subcortical neural circuits give rise to corresponding changes in the processing of threats and rewards from infancy to adulthood. We discuss how these developmental trajectories are altered by experiential factors, such as early-life stress, and highlight the relevance of this research for understanding the developmental onset and treatment of psychiatric disorders characterized by dysregulation of motivated behavior.

[Social environment, biological embedding and social inequalities in health]

The social gradient in health refers to the fact that the higher individuals rise in the social hierarchy, the better is their health. Understanding the construction of this gradient is a major challenge in social epidemiology. An original approach consists in looking at how the different exposures (chemical, physical, behavioural, psychosocial…) associated with the social environment are ultimately expressed at the biological level influencing health positively or negatively, referring to the concept of biological embedding. Data from animal models and life course epidemiology have shed new light on the biological mechanisms potentially at play. Recent discoveries from the field of epigenetics provide a better understanding of how the social environment, especially the early environment, can influence biological functioning over the long term or even over several generations. The work on the biological embedding of the social environment in connection with epigenetics still needs to be very largely consolidated, but could constitute a change of perspective in human biology, particularly by reconsidering the influence of the environment on biological functioning, which is not without consequences in terms of public health interventions.

Developmental plasticity: Bridging research in evolution and human health

Early life experiences can have profound and persistent effects on traits expressed throughout the life course, with consequences for later life behavior, disease risk, and mortality rates. The shaping of later life traits by early life environments, known as 'developmental plasticity', has been well-documented in humans and non-human animals, and has consequently captured the attention of both evolutionary biologists and researchers studying human health. Importantly, the parallel significance of developmental plasticity across multiple fields presents a timely opportunity to build a comprehensive understanding of this phenomenon. We aim to facilitate this goal by highlighting key outstanding questions shared by both evolutionary and health researchers, and by identifying theory and empirical work from both research traditions that is designed to address these questions. Specifically, we focus on: (i) evolutionary explanations for developmental plasticity, (ii) the genetics of developmental plasticity and (iii) the molecular mechanisms that mediate developmental plasticity. In each section, we emphasize the conceptual gains in human health and evolutionary biology that would follow from filling current knowledge gaps using interdisciplinary approaches. We encourage researchers interested in developmental plasticity to evaluate their own work in light of research from diverse fields, with the ultimate goal of establishing a cross-disciplinary understanding of developmental plasticity.

A cross-species comparison of abnormal behavior in three species of singly-housed old world monkeys

Abnormal behavior occurs in a number of captive nonhuman primate species and is often used as an indicator of welfare. However, reported levels of abnormal behavior often vary across species, making general welfare judgments difficult. The purpose of this study was to assess differences in levels of abnormal behavior and associated risk factors across three species of Old World monkeys in order to identify similarities and differences across species. The subjects were 415 (109 females) cynomolgus macaques (Macaca fascicularis), 365 (181 females) rhesus macaques (Macaca mulatta), and 331 (187 females) baboons (Papio hamadryas) that had been singly-housed for 30-120 days. A 5-min observation using one-zero sampling recorded the presence or absence of abnormal behavior for each animal. Macaques exhibited higher levels of abnormal behavior than baboons (29% vs. 14%; χ2(1) = 24.849, p < 0.001), but there was no difference between macaque species (30% vs. 28%; χ2(1) = 0.263, p = 0.608). Risk factors also varied. Overall, males exhibited greater levels of motor stereotypies (b = 0.425, p < 0.05), females greater levels of abnormal appetitive behavior (b = 1.703, p < 0.05), and older animals greater levels of self-directed behavior (b = 0.065, p < 0.05). However, macaques exhibited greater levels of motor stereotypy (b = 2.527, p < 0.001) and self-directed behavior (b = 2.968, p < 0.005) than did baboons. There was also a genus × sex interaction for abnormal appetitive behavior (b = -2.379, p < 0.01) and a genus × age interaction for motor stereotypy (b = -0.167, p < 0.05). These results demonstrate that differences in abnormal behavior exist across closely-related primate species. Therefore, a single species cannot be used generally as a model for abnormal behavior or animal welfare.

ALL OUR SONS: THE DEVELOPMENTAL NEUROBIOLOGY AND NEUROENDOCRINOLOGY OF BOYS AT RISK

Why are boys at risk? To address this question, I use the perspective of regulation theory to offer a model of the deeper psychoneurobiological mechanisms that underlie the vulnerability of the developing male. The central thesis of this work dictates that significant gender differences are seen between male and female social and emotional functions in the earliest stages of development, and that these result from not only differences in sex hormones and social experiences but also in rates of male and female brain maturation, specifically in the early developing right brain. I present interdisciplinary research which indicates that the stress-regulating circuits of the male brain mature more slowly than those of the female in the prenatal, perinatal, and postnatal critical periods, and that this differential structural maturation is reflected in normal gender differences in right-brain attachment functions. Due to this maturational delay, developing males also are more vulnerable over a longer period of time to stressors in the social environment (attachment trauma) and toxins in the physical environment (endocrine disruptors) that negatively impact right-brain development. In terms of differences in gender-related psychopathology, I describe the early developmental neuroendocrinological and neurobiological mechanisms that are involved in the increased vulnerability of males to autism, early onset schizophrenia, attention deficit hyperactivity disorder, and conduct disorders as well as the epigenetic mechanisms that can account for the recent widespread increase of these disorders in U.S. culture. I also offer a clinical formulation of early assessments of boys at risk, discuss the impact of early childcare on male psychopathogenesis, and end with a neurobiological model of optimal adult male socioemotional functions.

Attachment Figure's Regulation of Infant Brain and Behavior

Altricial infants (i.e., requiring parental care for survival), such as humans and rats, form an attachment to their caregiver and receive the nurturing and protections needed for survival. Learning has a strong role in attachment, as is illustrated by strong attachment formed to non-biological caregivers of either sex. Here we summarize and integrate results from animal and human infant attachment research that highlights the important role of social buffering (social presence) of the stress response by the attachment figure and its effect on infant processing of threat and fear through modulation of the amygdala. Indeed, this work suggests the caregiver switches off amygdala function in rodents, although recent human research suggests a similar process in humans and nonhuman primates. This cross-species analysis helps provide insight and unique understanding of attachment and its role in the neurobiology of infant behavior within attachment.

Antidepressant responsiveness in adulthood is permanently impaired after neonatal destruction of the neurogenic pool

The dynamic turnover of hippocampal neurons is implicated in the regulation of cognitive and affective behavior. Extending our previous demonstration that administration of dexamethasone (ND) to neonatal rats depletes the resident population of neural precursor cells (NPC) and restrains the size of the neurogenic regions, we now show that the adverse effects of ND persist into adulthood. Specifically, ND impairs repletion of the neurogenic pool and neurogenesis; ND also compromises cognitive performance, the ability to actively adapt to an acute stressor and, the efficacy of glucocorticoid (GC) negative feedback. Interestingly, although ND depletes the neurogenic pool, it does not permanently abolish the proliferative machinery of the residual NPC population; however, ND increases the susceptibility of hippocampal granule neurons to apoptosis. Although the antidepressant fluoxetine (FLX) reverses the latter phenomenon, it does not replenish the NPC pool. Treatment of ND-treated adult rats with FLX also improves GC negative feedback, albeit without rescuing the deleterious effects of ND on behavior. In summary, ND leads to protracted disruption of mental functions, some of which are resistant to antidepressant interventions. We conclude that manipulation of the NPC pool during early life may jeopardize the therapeutic potential of antidepressants in adulthood.

Early life adversity alters normal sex-dependent developmental dynamics of DNA methylation

Studies in rodents, nonhuman primates, and humans suggest that epigenetic processes mediate between early life experiences and adult phenotype. However, the normal evolution of epigenetic programs during child development, the effect of sex, and the impact of early life adversity on these trajectories are not well understood. This study mapped the genome-wide DNA methylation changes in CD3+ T lymphocytes from rhesus monkeys from postnatal day 14 through 2 years of age in both males and females and determined the impact of maternal deprivation on the DNA methylation profile. We show here that DNA methylation profiles evolve from birth to adolescence and are sex dependent. DNA methylation changes accompany imposed weaning, attenuating the difference between males and females. Maternal separation at birth alters the normal evolution of DNA methylation profiles and targets genes that are also affected by a later stage maternal separation, that is, weaning. Our results suggest that early life events dynamically interfere with the normal developmental evolution of the DNA methylation profile and that these changes are highly effected by sex.

The ethical challenges of animal research

In 1966, Henry K. Beecher published an article entitled "Ethics and Clinical Research" in the New England Journal of Medicine, which cited examples of ethically problematic human research. His influential paper drew attention to common moral problems such as inadequate attention to informed consent, risks, and efforts to provide ethical justification. Beecher's paper provoked significant advancements in human research policies and practices. In this paper, we use an approach modeled after Beecher's 1966 paper to show that moral problems with animal research are similar to the problems Beecher described for human research. We describe cases that illustrate ethical deficiencies in the conduct of animal research, including inattention to the issue of consent or assent, incomplete surveys of the harms caused by specific protocols, inequitable burdens on research subjects in the absence of benefits to them, and insufficient efforts to provide ethical justification. We provide a set of recommendations to begin to address these deficits.

Factors influencing alopecia and hair cortisol in rhesus macaques (Macaca mulatta)

BACKGROUND

Alopecia can occur in captive non-human primates, but its etiology is poorly understood. The purpose of this study was to assess alopecia and hair cortisol in rhesus monkeys and to identify the potential risk factors.

METHODS

Subjects were 117 rhesus monkeys at two National Primate Research Centers. Photographs and hair samples were obtained during routine physicals. Photographs were analyzed using Image J software to calculate hair loss, and hair samples were assayed for cortisol.

RESULTS

Age, days singly housed, and their interactions contributed to the alopecia model for both facilities. Sex and location changes contributed to the hair cortisol model for Facility 1; sedations contributed for Facility 2. Alopecia and hair cortisol were associated at Facility 1.

CONCLUSIONS

Captive management practices can affect alopecia and hair cortisol. However, there are facility differences in the relationship between alopecia and hair cortisol and in the effect of intrinsic variables and management procedures.

Adversity-induced relapse of fear: neural mechanisms and implications for relapse prevention from a study on experimentally induced return-of-fear following fear conditioning and extinction

The efficacy of current treatments for anxiety disorders is limited by high relapse rates. Relapse of anxiety disorders and addiction can be triggered by exposure to life adversity, but the underlying mechanisms remain unexplored. Seventy-six healthy adults were a priori selected for the presence or absence of adverse experiences during childhood (CA) and recent past (RA; that is, past 12 months). Participants underwent fear conditioning (day 1) and fear extinction and experimental return-of-fear (ROF) induction through reinstatement (a model for adversity-induced relapse; day 2). Ratings, autonomic (skin conductance response) and neuronal activation measures (functional magnetic resonance imaging (fMRI)) were acquired. Individuals exposed to RA showed a generalized (that is, not CS- specific) fear recall and ROF, whereas unexposed individuals showed differential (that is, CS+ specific) fear recall and ROF on an autonomic level despite no group differences during fear acquisition and extinction learning. These group differences in ROF were accompanied by corresponding activation differences in brain areas known to be involved in fear processing and differentiability/generalization of ROF (that is, hippocampus). In addition, dimensional measures of RA, CA and lifetime adversity were negatively correlated with differential skin conductance responses (SCRs) during ROF and hippocampal activation. As discriminating signals of danger and safety, as well as a tendency for overgeneralization, are core features in clinically anxious populations, these deficits may specifically contribute to relapse risk following exposure to adversity, in particular to recent adversity. Hence, our results may provide first and novel insights into the possible mechanisms mediating enhanced relapse risk following exposure to (recent) adversity, which may guide the development of effective pre- and intervention programs.

Effects of early life stress on amygdala and striatal development

Species-expected caregiving early in life is critical for the normative development and regulation of emotional behavior, the ability to effectively evaluate affective stimuli in the environment, and the ability to sustain social relationships. Severe psychosocial stressors early in life (early life stress; ELS) in the form of the absence of species expected caregiving (i.e., caregiver deprivation), can drastically impact one's social and emotional success, leading to the onset of internalizing illness later in life. Development of the amygdala and striatum, two key regions supporting affective valuation and learning, is significantly affected by ELS, and their altered developmental trajectories have important implications for cognitive, behavioral and socioemotional development. However, an understanding of the impact of ELS on the development of functional interactions between these regions and subsequent behavioral effects is lacking. In this review, we highlight the roles of the amygdala and striatum in affective valuation and learning in maturity and across development. We discuss their function separately as well as their interaction. We highlight evidence across species characterizing how ELS induced changes in the development of the amygdala and striatum mediate subsequent behavioral changes associated with internalizing illness, positing a particular import of the effect of ELS on their interaction.

Prior facility affects alopecia in adulthood for rhesus macaques

Alopecia has proven to be a persistent problem for captive macaques; many cases continue to elude explanations and effective treatments. Although almost all captive populations exhibit alopecia rates higher than those seen in the wild, there also appear to be wide ranges in rates reported across primate facilities. In this study we looked at alopecia ratings for rhesus macaques (Macaca mulatta) obtained from five primary suppliers and currently housed at the Washington National Primate Research Center (WaNPRC). There were significant differences in alopecia ratings based on prior facility, despite the fact that animals had left their prior facilities at least 10 months previously and 60% had left more than 2 years previously. Possible explanations for the facility effect may include longer than anticipated time lines for alopecia amelioration, early experience effects, and genetic contributions. Our results should provide a cautionary note for those evaluating alopecia, treatments for alopecia, and the current environments of alopecic animals. It is possible that not all alopecia is caused, or can be ameliorated, by changes in the immediate environment. Am. J. Primatol. 79:e22551, 2017. © 2016 Wiley Periodicals, Inc.

Associations between early life experience, chronic HPA axis activity, and adult social rank in rhesus monkeys

Early life experience and socioeconomic status (SES) are well-established predictors of health outcomes in people. Both factors likely influence health outcomes via hypothalamic-pituitary-adrenal (HPA) axis regulation. However, it is unclear how early experience and HPA axis activity influence adult social status. We studied differentially reared female rhesus monkeys (Macaca mulatta, N = 90) as models to test the hypothesis that chronic HPA axis activity assessed via hair cortisol concentrations (HCCs) mediated the relationship between early life experience and adult social rank. We found that mother-peer-reared (MPR) monkeys acquired higher social ranks than either of the two nursery-reared (NR) groups (peer-reared, PR, or surrogate-peer-reared, SPR monkeys) (β = -0.07, t₍₈₉₎ = -2.16, p = 0.034). We also found that MPR HCCs were lower during the juvenile period at 18 months (F_(2,25) = 3.49, p = 0.047). Furthermore, for MPR but not NR monkeys, changes in HCCs from 18 to 24 months (r_(s) = -0.627, p = 0.039) and adult HCCs (r_(s) = -0.321, p = 0.03) were negatively correlated with adult social rank. These findings suggest that chronic HPA axis regulation in juvenility, and perhaps in adulthood, may influence adult social status for primates that experience typical early rearing. However, early life adversity may result in dissociation between neuroendocrine stress regulation and adult social competence, which may be risk factors for adverse health outcomes.

Persistent Effects of Peer Rearing on Abnormal and Species-Appropriate Activities but Not Social Behavior in Group-Housed Rhesus Macaques (Macaca mulatta)

Nursery rearing of rhesus macaques (Macaca mulatta) alters behaviors but may be necessitated by maternal rejection or death, for research protocols, or for derivation of SPF colonies. The Tulane National Primate Research Center maintains a nursery-reared colony that is free from 9 pathogens as well as a mother-reared colony free from 4 pathogens, thus affording an opportunity to assess the outcomes of differential rearing. Nursery-reared macaques had continuous contact with 2 peers and an artificial surrogate (peer rearing). Focal sampling (432 h) was collected on the behavior of 32 peer-reared and 40 mother-reared subjects (age, 1 to 10 y; immature group, younger than 4 y; adult group 4 y or older). All animals were housed outdoors in like-reared social groups of 3 to 8 macaques. Contrary to expectation, no rearing effects on affiliative or agonistic social behaviors were detected. Compared with mother-reared subjects, peer-reared macaques in both age classes had elevated levels of abnormal appetitive, abnormal self-directed, and eating behaviors and lower levels of locomoting and vigilance (highly alert to activities in surrounding environment); a trend toward reduced foraging was detected. Immature but not adult peer-reared monkeys demonstrated more enrichment-directed behavior and drinking and a trend toward more anxiety-related behavior and inactivity. No new rearing effects were detected in adults that had not been detected in immature subjects. Results suggest that modern peer-rearing practices may not result in inevitable perturbations in aggressive, rank-related, sexual, and emotional behavior. However, abnormal behaviors may be lifelong issues once they appear.

The Long-Run Impact of Cash Transfers to Poor Families

We estimate the long-run impact of cash transfers to poor families on children's longevity, educational attainment, nutritional status, and income in adulthood. To do so, we collected individual-level administrative records of applicants to the Mothers' Pension program-the first government-sponsored welfare program in the United States (1911-1935)-and matched them to census, WWII, and death records. Male children of accepted applicants lived one year longer than those of rejected mothers. They also obtained one-third more years of schooling, were less likely to be underweight, and had higher income in adulthood than children of rejected mothers.

Mental Health and Self-Esteem of Institutionalized Adolescents Affected by Armed Conflict

The primary purpose of this paper was to compare the epidemiology of mental health problems and self-esteem of conflict hit adolescents living in charitable seminaries with their counterparts brought up in natural homes. Substantive body of the literature illustrates the emotional and behavioral issues experienced by these adolescents. In this study, 27 adolescents from a charitable Muslim seminary and 30 adolescents from a regular school were recruited. Self-report measures and clinical interview were used to measure mental health and self-esteem. The findings indicate that adolescents in institution setting may not be having mental health and self-esteem-related issues when compared to adolescents living in intact by parent homes. While the authors acknowledge the limitations of the study, these findings need further research to examine the causes for these differences.