Neither antecedent nor consequence: Developmental integration of chronic stress, pubertal timing, and conditionally adapted stress response

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.

The interplay of oxytocin and sex hormones

The neuropeptide oxytocin has historically been associated with reproduction and maternal behavior. However, more recent research has uncovered that oxytocin has a much wider range of roles in physiology and behavior. Despite the excitement surrounding potential therapeutical applications of intranasally administered oxytocin, the results of these intervention studies have been inconsistent. Various reasons for these mixed results have been proposed, which tend to focus on methodological issues, such as study design. While methodological issues are certainly important, emerging evidence suggests that the interaction between oxytocin and sex hormones may also account for these varied findings. To better understand the purpose and function of the interaction of oxytocin with sex hormones, with a focus on estrogens, progesterone, and testosterone, we conducted a comprehensive thematic review via four perspectives: evolutionary, developmental, mechanistic, and survival. Altogether, this synergistic approach highlights the critical function of sex hormone activity for accomplishing the diverse roles of oxytocin via the modulation of oxytocin release and oxytocin receptor activity, which is also likely to contribute to the heterogeneity of outcomes after oxytocin administration.

Childhood adversity and accelerated reproductive events: a systematic review and meta-analysis

OBJECTIVE

Accelerated female reproductive events represent the early onset of reproductive events involving puberty, menarche, pregnancy loss, first sexual intercourse, first birth, parity, and menopause. This study aimed to explore the association between childhood adversity and accelerated female reproductive events.

DATA SOURCES

PubMed, Web of Science, and Embase were systematically searched from September 22, 2022 to September 23, 2022.

STUDY ELIGIBILITY CRITERIA

Observational cohort, cross-sectional, and case-control studies in human populations were included if they reported the time of reproductive events for female individuals with experience of childhood adversity and were published in English.

METHODS

Two reviewers independently screened studies, obtained data, and assessed study quality, and conflicts were resolved by a third reviewer. Dichotomous outcomes were evaluated using meta-analysis, and pooled odds ratios and 95% confidence intervals were generated using random-effects models. Moderation analysis and meta-regression were used to investigate heterogeneity.

RESULTS

In total, 21 cohort studies, 9 cross-sectional studies, and 3 case-control studies were identified. Overall, female individuals with childhood adversity were nearly 2 times more likely to report accelerated reproductive events than those with no adversity exposure (odds ratio, 1.91; 95% confidence interval, 1.33-2.76; I2=99.6%; P<.001). Moderation analysis indicated that effect sizes for the types of childhood adversity ranged from an odds ratio of 1.61 (95% confidence interval, 1.23-2.09) for low socioeconomic status to 2.13 (95% confidence interval, 1.14-3.99) for dysfunctional family dynamics. Among the 7 groups based on different reproductive events, including early onset of puberty, early menarche, early sexual initiation, teenage childbirth, preterm birth, pregnancy loss, and early menopause, early sexual initiation had a nonsignificant correlation with childhood adversity (odds ratio, 2.70; 95% confidence interval, 0.88-8.30; I2=99.9%; P<.001). Considerable heterogeneity (I2>75%) between estimates was observed for over half of the outcomes. Age, study type, and method of data collection could explain 35.9% of the variance.

CONCLUSION

The literature tentatively corroborates that female individuals who reported adverse events in childhood are more likely to experience accelerated reproductive events. This association is especially strong for exposure to abuse and dysfunctional family dynamics. However, the heterogeneity among studies was high, requiring caution in interpreting the findings and highlighting the need for further evaluation of the types and timing of childhood events that influence accelerated female reproductive events.

Skin-deep Resilience and Early Adolescence: Neighborhood Disadvantage, Executive Functioning, and Pubertal Development in Minority Youth

Skin-deep resilience, in which youth overcome adversity and achieve success in psychological and academic domains but at a cost to their physiological well-being, has been documented in late adolescence and adulthood. However, its potential to emerge at earlier developmental stages is unknown. To address this gap, secondary data analyses were executed using waves 1 and 2 of the Adolescent Brain Cognitive Development study (n = 7712; ages 9-10 years at baseline [mean: 9.92; SD = 0.63]; 47.1% female; 66.1% White, 13.4% Black, and 20.6% Hispanic). The results indicated high levels of executive functioning were associated with improved psychological and behavioral outcomes at one-year follow-up. However, for racial and ethnic minority (i.e., Black or Hispanic) youth from disadvantaged neighborhoods, high levels of executive functioning were also associated with accelerated pubertal development. No significant interaction was observed among White youth. The findings suggest the skin-deep resilience pattern may be evident in early adolescence.

Social jetlag is associated with adverse cardiometabolic latent traits in early adolescence: an observational study

Introduction

Adolescence is marked by physiological and social changes, such as puberty, increased responsibilities and earlier school start times. This often leads to insufficient sleep on school nights and the need to compensate for lost sleep on weekends, causing a misalignment between biological and social times, which has been termed social jetlag (SJL). SJL triggers stress responses and is associated with several negative health outcomes, including higher cardiometabolic risk in adults. In adolescence, however, SJL has only been consistently related to increases in adiposity but its association with other cardiometabolic indicators are unclear.

Method

In a sample of 278 healthy early adolescents (9-15 years of age; 168 girls) we investigated: 1) whether self-reported SJL is associated (using path analyses) with a cardiometabolic status latent factor obtained by testing the best fitting model via confirmatory factor analyses from an initial set of eight indicators [body mass index (BMI), waist/height ratio, triglyceride concentration, diastolic and systolic blood pressure, glycated hemoglobin, total cholesterol/high-density lipoprotein ratio (chol/HDL), and % body fat]; and 2) whether age and/or pubertal status influence the association between SJL and cardiometabolic status.

Result

We found that, for girls, higher SJL was associated with more adverse cardiometabolic latent scores (the shared variance of BMI, waist/height ratio, chol/HDL and systolic blood pressure, which had acceptable model fit indices). However, the role of age and pubertal status in this association was unclear for both sexes.

Discussion

SJL was associated with adverse cardiometabolic latent traits beyond increases in adiposity in this observational study in early female adolescents. Because disruptions of circadian rhythms are believed to lead to dysregulated energy homeostasis and not vice-versa, our findings highlight the need for sleep interventions in adolescence to help reduce the global burden of cardiometabolic ill health, especially in girls.

Country-level gender inequality is associated with structural differences in the brains of women and men

Gender inequality across the world has been associated with a higher risk to mental health problems and lower academic achievement in women compared to men. We also know that the brain is shaped by nurturing and adverse socio-environmental experiences. Therefore, unequal exposure to harsher conditions for women compared to men in gender-unequal countries might be reflected in differences in their brain structure, and this could be the neural mechanism partly explaining women's worse outcomes in gender-unequal countries. We examined this through a random-effects meta-analysis on cortical thickness and surface area differences between adult healthy men and women, including a meta-regression in which country-level gender inequality acted as an explanatory variable for the observed differences. A total of 139 samples from 29 different countries, totaling 7,876 MRI scans, were included. Thickness of the right hemisphere, and particularly the right caudal anterior cingulate, right medial orbitofrontal, and left lateral occipital cortex, presented no differences or even thicker regional cortices in women compared to men in gender-equal countries, reversing to thinner cortices in countries with greater gender inequality. These results point to the potentially hazardous effect of gender inequality on women's brains and provide initial evidence for neuroscience-informed policies for gender equality.

Longitudinal patterns of neuroendocrine coupling from middle childhood to early adolescence

Recent scholarship has highlighted the importance of understanding relations between hormones, rather than studying hormones in isolation. Considering neuroendocrine coupling, or the coordination of hypothalamic-pituitary-adrenal axis and hypothalamic-pituitary-gonadal axis hormones over time, is one way to investigate how systems governing stress responsiveness and pubertal development covary during critical periods. To date, however, most work has considered hormone coupling cross-sectionally. The current study investigated neuroendocrine coupling in a longitudinal sample from the Northeastern United States. Youth (N = 437, 53% male, 90% White) provided saliva samples for analysis of diurnal hormone activity at ages 9 (three samples per day across 3 days) and 12 (one sample per day on the same weekday for 4 weeks). At both timepoints, samples collected 30-min after waking were assayed for cortisol, dehydroepiandrosterone (DHEA), and testosterone. Multilevel growth modeling was used to determine how levels of morning cortisol changed in tandem with DHEA and testosterone. Morning cortisol-DHEA coupling varied by child sex, as males' cortisol-DHEA diminished over time, especially among pubertally advanced males. Females, in contrast, demonstrated strengthening cortisol-DHEA coupling over time, especially more pubertally advanced females. Morning cortisol-testosterone coupling did not vary by sex or pubertal status, demonstrating strengthening associations between ages 9 and 12. The current findings contribute to the literature on hormone coupling across development and expand this work into an earlier developmental phase than previously investigated.

Family environmental antecedents of pubertal timing in girls and boys: A review and open questions

Across nonhuman species, pubertal timing is affected by the social environment, with consequences for reproductive success and behavior. In human beings, variations in pubertal timing have not been systematically examined in relation to social environmental antecedents, although their psychological consequences are well documented. This paper focuses on links in human beings between pubertal timing and the childhood social environment, with several sections: A review of studies relating pubertal timing to the family context, a key aspect of the social environment; challenges in studying the issue; and opportunities for future work that takes advantage of and creates links with evidence in other species. The review shows that pubertal timing in girls is accelerated by adversity in aspects of the early family social context, with effects small in size; data in boys are not sufficient to enable conclusions. Inferences from existing studies are limited by variations in conceptualizations and measurement of relevant aspects of puberty and of the family social environment, and by methodological issues (e.g., reliance on existing data, use of retrospective reports, nonrandom missing data). Open questions remain about the nature, mechanisms, and specificity of the links between early family social environment and pubertal timing (e.g., form of associations, consideration of absence of positive experiences, role of timing of exposure). Animal studies provide a useful guide for addressing these questions, by delineating potential hormonal mechanisms that underlie links among social context, pubertal timing, and behavior, and encouraging attention to aspects of the social environment outside the family, especially peers.

Sex-Specific Associations Between Trauma Exposure, Pubertal Timing, and Anxiety in Black Children

Recent research has linked early life stress (ELS), such as trauma exposure, with early puberty. Early puberty has also been identified as a risk factor for poor mental health outcomes. However, these two paths have primarily been examined independently. In addition, more studies have examined these associations in girls than boys, and findings for boys remain mixed. We hypothesized that early puberty (relative to peers) would be positively associated with both prior trauma exposure and concurrent anxiety symptoms. We anticipated that these associations might differ by sex. We tested these hypotheses within a cross-sectional sample of 133 8- to 13-year-old Black girls and boys with trauma exposure. The association between trauma and accelerated pubertal timing was sex-specific: it was positive for girls and negative for boys. We stratified subsequent analyses by sex. Regression analyses indicated that early puberty relative to peers predicted more anxiety symptoms for girls but not boys, after accounting for trauma exposure. A statistical mediation analysis indicated that, for girls, the positive association between trauma exposure and anxiety was partially mediated by pubertal timing. These results indicate that trauma exposure may have sex-specific effects on pubertal timing and anxiety risk in Black children. We also found that, for girls, trauma may increase risk for adverse outcomes by prompting earlier puberty, which is linked to higher anxiety. These findings are consistent with cascading effects of trauma across development, and highlight the need for further study of sex-specific mechanisms.

Family Experiences and Parent Personality as Antecedents of Pubertal Timing in Girls and Boys

Pubertal timing may be influenced by typical variations in early family environmental events, but questions remain concerning the roles of specific parenting factors, developmental age of exposure to events, moderation by child temperament, and comparability of effects for girls and boys. This study focused on these questions utilizing longitudinal data from 733 same-sex twins (45% girls) in the U.S.; family context was measured at ages 1-3, 4-5, and 6-7 years and pubertal status was assessed annually via self-report at ages 9-15, enabling estimates of pubertal timing. Home environment at ages 4-5 years predicted pubertal timing better than home environment at other ages for both girls and boys, but parent personality was more predictive than home experiences (e.g., divorce, parental harshness, family conflict). Thus, effects of family environment must be considered within the context of parent characteristics, encouraging caution in implicating early environmental experiences as direct influences on early pubertal timing.

Early Pubertal Timing Mediates the Association between Low Socioeconomic Status and Poor Attention and Executive Functioning in a Diverse Community Sample of Adolescents

Low socioeconomic status (SES) may be associated with earlier pubertal timing and impaired attention and executive function (EF) in youth; however, whether pubertal timing mediates the relation between SES and attention or executive functioning remains unclear. Structural equation models tested concurrent and prospective relations between SES, pubertal timing, and attention and executive functioning measures in a gender and racially diverse sample of adolescents (N = 281, 45.6% male, 50.5% White/Caucasian, 46.3% Black/African American, 3.2% Biracial/other, and 44.5% low SES; complete data were not available on some measures). Youth from low SES families experienced earlier pubertal timing, and this accelerated development was associated with worse performance on attention and executive functioning tasks, both concurrently and longitudinally. These findings highlight a pathway by which youth from low socioeconomic backgrounds may develop worse attention and executive functioning abilities during adolescence.

Early Puberty and Telomere Length in Preadolescent Girls and Mothers

OBJECTIVE

To test the association between early puberty and telomere length in preadolescent girls and mothers from a large representative sample of US females.

STUDY DESIGN

We analyzed data from 1194 preadolescent girls and 2421 mothers from the Fragile Families and Child Wellbeing Study. Participants were from a population-based birth cohort (1998-2000) born in large US cities. Telomere length was assessed by quantitative polymerase chain reaction from saliva samples provided by preadolescent girls and mothers of preadolescent youth. Mothers completed a questionnaire about their child's pubertal development to determine concurrent Tanner stages and provided self-reports of her own age at menarche. Linear regression models were used to estimate the association between pubertal development (status and timing) and telomere length.

RESULTS

Early pubertal timing but not pubertal status was associated with shorter telomere length in preadolescent girls (P < .01). Early age at menarche was associated with shorter telomere length in a sample of mothers of preadolescent youth (P < .05).

CONCLUSIONS

Results provide evidence for the association between early puberty and shorter telomeres evidenced by associations in both preadolescent girls and mothers. Future research should address the limitations of this study by using longitudinal measurements of pubertal development assessed through medical examinations and repeated assessments of telomere length to capture telomere attrition.

Childhood Adversity and Pubertal Development Among Puerto Rican Boys and Girls

OBJECTIVE

Evidence stemming largely from retrospective studies suggests that childhood adversity (CA) is associated with earlier age at menarche, a marker of pubertal timing, among girls. Little is known about associations with pubertal tempo among boys or racial/ethnic minorities. We examined the association between CA and timing and tempo of pubertal development among boys and girls.

METHODS

The Boricua Youth Study is a longitudinal study of Puerto Rican youth residing in the San Juan metro area in Puerto Rico and the South Bronx, New York. CA was based on caretaker reports of parental loss and parental maladjustment and youth reports of child maltreatment and exposure to violence. Youth completed the Pubertal Development Scale (PDS) yearly for 3 years. In linear mixed models stratified by sex, we examined the association between CA and pubertal timing and tempo, adjusting for site, socioeconomic status, and age.

RESULTS

Among the 1949 children who were 8 years or older by wave 3, cumulative CA was associated with higher PDS scores among girls compared with girls not exposed to CA (PDS score: 2.63 [95% confidence interval {CI} = 2.55-2.71] versus 2.48 [95% CI = 2.37-2.58]). In contrast, among boys, experiencing adversities was associated with lower pubertal developmental stage or later timing (PDS: 1.77 [95% CI = 1.67-1.87] versus 1.97 [95% CI = 1.85-2.10]) compared with those not exposed to adversities.

CONCLUSIONS

Associations between CA and pubertal development may vary by sex. Understanding the etiological role of adversities on pubertal development and identifying targets for intervention are of utmost importance in ameliorating the impact of CA on child health.

Hormones and human developmental plasticity

Natural selection favors the evolution of mechanisms that optimize the allocation of resources and time among competing traits. Hormones mediate developmental plasticity, the changes in the phenotype that occur during ontogeny. Despite their highly conserved functions, the flexibilities of human hormonal systems suggest a strong history of adaptation to variable environments. Physiological research on developmental plasticity has focused on the early programming effects of stress, the hypothalamus-pituitary-adrenal axis (HPAA) and the hypothalamus-pituitary-gonadal axis (HPGA) during critical periods, when the hormones produced have the strongest influence on the developing brain. Often this research emphasizes the maladaptive effects of early stressful experiences. Here we posit that the HPAA and HPAG systems in human developmental plasticity have evolved to be responsive to complex and dynamic problems associated with human sociality. The lengthy period of human offspring dependency, and its associated brain development and risks, is linked to the uniquely human combination of stable breeding bonds, extensive paternal effort in a multi-male group, extended bilateral kin recognition, grandparenting, and controlled exchange of mates among kin groups. We evaluate an evolutionary framework that integrates proximate physiological explanations with ontogeny, phylogeny, adaptive function, and comparative life history data.

Extending the toxic stress model into adolescence: Profiles of cortisol reactivity

The toxic stress model posits that extended activation of stress response systems in the absence of a supportive relationship with an adult may over time lead to physiological alterations to these same systems, and ultimately to poorer physical and mental health outcomes. However, empirical tests of model hypotheses in adolescence, a critical period of development, are lacking. This study expands the toxic stress model to include more developmentally-appropriate risk and protective factors for adolescents experiencing overwhelming and uncontrollable stressors. Data were collected for a study of early adolescents from urban low-income households (N = 101; 10-12 years old; 59% female). Participants and a caregiver completed questionnaires; youths completed the modified Trier Social Stress Task alone and provided six saliva samples. Using latent profile analysis, three profiles of cortisol reactivity were identified in early adolescents exposed to chronic environmental stress: Elevated and Reactive (11%), Moderate and Non-Reactive (26%), and Blunted and Non-Reactive (63%). In accordance with the toxic stress model, exposure to more community violence and less family support were associated with blunted cortisol reactivity, and Reactive profile membership was associated with fewer trauma symptoms. Overall, the findings provide empirical support for the extension of the toxic stress model in early adolescence through the application of developmentally-sensitive measures and provide implications for future interventions.

Co-activation of SAM and HPA responses to acute stress: A review of the literature and test of differential associations with preadolescents' internalizing and externalizing

Understanding co-activation patterns of the hypothalamic-pituitary-adrenal axis (HPA) and sympathetic adrenal medullary (SAM) during early adolescence may illuminate risk for development of internalizing and externalizing problems. The present study advances empirical work on the topic by examining SAM-HPA co-activation during both the reactivity and recovery phases of the stress response following acute stress exposure. Fourth and fifth grade boys and girls (N = 149) provided cortisol and alpha-amylase via saliva at seven times throughout a 95-min assessment in which they were administered the modified Trier Social Stress Test. Parents reported on adolescents' life stress, pubertal development, medication use, and externalizing problems. Adolescents reported their own internalizing symptoms. Multiple linear regressions tested both direct and interactive effects of SAM and HPA reactivity and recovery on internalizing and externalizing problems. Results from these analyses showed that whereas SAM and HPA reactivity interacted to predict internalizing symptoms, it was their interaction during the recovery phase that predicted externalizing. Concurrent high SAM and HPA reactivity scores predicted high levels of internalizing and concurrently low SAM and HPA recovery scores predicted high levels of externalizing. Implications of the findings for further study and clinical application are discussed.

Developmental Adaptation to Stress: An Evolutionary Perspective

The assumption that early stress leads to dysregulation and impairment is widespread in developmental science and informs prevailing models (e.g., toxic stress). An alternative evolutionary–developmental approach, which complements the standard emphasis on dysregulation, proposes that early stress may prompt the development of costly but adaptive strategies that promote survival and reproduction under adverse conditions. In this review, we survey this growing theoretical and empirical literature, highlighting recent developments and outstanding questions. We review concepts of adaptive plasticity and conditional adaptation, introduce the life history framework and the adaptive calibration model, and consider how physiological stress response systems and related neuroendocrine processes may function as plasticity mechanisms. We then address the evolution of individual differences in susceptibility to the environment, which engenders systematic person–environment interactions in the effects of stress on development. Finally, we discuss stress-mediated regulation of pubertal development as a case study of how an evolutionary–developmental approach can foster theoretical integration.