Prenatal exposure to maternal psychosocial stress and HPA axis regulation in young adults

Epidemiological studies have reported associations between measures of size and weight at birth and disease risk in later life. Alteration in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis in response to prenatal stress has been proposed as one underlying mechanism. The present study investigated in humans the association of prenatal psychosocial stress exposure with subsequent HPA axis regulation in adult life, with a focus on measures of response to challenge and feedback sensitivity. Healthy young adults whose mothers experienced severe stress during their pregnancy in form of major negative life events (e.g. death of someone close; prenatal stress (PS) group, n = 31) and an age-matched comparison group (CG, n = 30) underwent the Trier Social Stress Test (TSST) and a 1 μg ACTH_1-24 stimulation test. In addition, a diurnal cortisol profile was assessed. ACTH concentrations following a standardized behavioural challenge paradigm (TSST) were marginally significantly higher in PS subjects than in CG subjects (p = .06). Pre-TSST adrenocortical (cortisol) levels were lower (p = .007), whereas the increase in cortisol in response to the TSST was higher (p = .03) in PS subjects compared to CG subjects. Cortisol concentrations following a pharmacological stimulation test simulating pituitary activity (ACTH_1-24 test) were significantly lower in PS than in CG subjects (p = .006). No differences emerged between the two groups in basal diurnal cortisol levels. This study provides first evidence in humans of an association between prenatal psychosocial stress exposure and subsequent alterations in the regulation of the HPA axis.     

Perceived discrimination and diurnal cortisol: examining relations among Mexican American adolescents

Perceived discrimination remains a salient and significant environmental stressor for ethnic and racial minority youth. Although many studies have examined the impact of racial/ethnic discrimination on mental health symptomatology and physical health, little is known of the potential physiological processes underlying such experiences, especially during adolescence. In an attempt to understand how varying perceptions of discrimination relate to functioning of the hypothalamic-pituitary-adrenal axis (HPA axis), the current study examined the relation between Mexican American adolescents' (N = 100, M(age) = 15.3 years old) perceptions of discrimination and aspects of their diurnal cortisol profiles. Three salivary samples (wakeup, +30 waking, bedtime) were collected across 3 days (total of 9 samples). Utilizing multi-level modeling, results revealed that adolescents' perceived discrimination related to greater overall cortisol output (area under the curve; AUC) after controlling for other life stressors, depressive symptoms, family income, acculturation level, daily stress levels and daily behaviors. Findings also revealed that perceived discrimination was marginally related to a steeper cortisol awakening response (CAR). Together, these findings suggest that perceived discrimination is a salient and impactful stressor for Mexican American adolescents. Understanding the physiological correlates of discrimination can provide insight into larger health disparities among ethnic and racial minority individuals.     

High self-perceived stress and many stressors, but normal diurnal cortisol rhythm, in adults with ADHD (attention-deficit/hyperactivity disorder)

Attention-deficit/hyperactivity disorder (ADHD) in adults is associated with significant impairment in many life activities and may thus increase the risk of chronic stress in everyday life. We compared adults with a DSM-IV ADHD diagnosis (n = 28) with healthy controls (n = 28) regarding subjective stress and amounts of stressors in everyday life, diurnal salivary cortisol in the everyday environment and salivary cortisol before and after cognitive stress in a laboratory setting. The association between cortisol concentrations and impulsivity was also investigated. Consistent with assumptions, individuals with ADHD reported significantly more self-perceived stress than controls, and subjective stress correlated with the amount of stressors in everyday life. The two groups were comparable with respect to overall diurnal cortisol levels and rhythm, as well as in pre- and post-stress cortisol concentrations. Post-stress cortisol (but not baseline cortisol) concentration was positively correlated with impulsivity. The group with high post-stress cortisol also reported more symptoms of depression and anxiety, as well as self-perceived stress and stressors in every-day life. The diagnosis of ADHD significantly increased the risk of belonging to the group with high post-stress cortisol levels. The results in this study warrant a focus not only on the primary diagnosis of ADHD, but also calls for a broader assessment of stressors and subjective stress in everyday life, as well as support comprising stress management and coping skills.     

Beyond physiological hypoarousal: The role of life stress and callous-unemotional traits in incarcerated adolescent males

The development of antisocial behavior in youth has been examined with neurobiological theories that suggest that adolescents who are less responsive to their environments are less likely to develop empathy in the absence of extant physiological arousal. However, little attention is paid to these individuals' social context. Individuals with adverse early experiences can also exhibit attenuated physiological arousal. The current investigation examines whether psychopathic symptoms or life stress exposure is associated with cortisol and its diurnal rhythm within 50 incarcerated adolescent boys (14–18 years old). Ten saliva cortisol samples were collected 1–2 weeks after admission to a maximum-security juvenile facility. Hierarchical Linear Modeling distinguished waking cortisol levels, the awakening response (CAR) and the diurnal rhythm. Multiple interviews and self-report measures of CU traits and stressor exposure were collected. Boys with higher levels of CU traits or greater life stress exposure had flat diurnal rhythms and a steeper awakening response in analyses with lifetime stress exposure specifically. Nonetheless, boys who were elevated on both CU traits and prior stress exposure had steeper diurnal rhythms. These results extend neurobiological theories of cortisol and illustrate that boys with the combination of severe stress with CU traits have a unique physiological profile.     

Negative emotionality, depressive symptoms and cortisol diurnal rhythms: analysis of a community sample of middle-aged males

Prior research suggests that individuals with particular personality traits, like negative emotionality, are at greater risk for adverse health outcomes. Despite bivariate associations between negative emotionality, depressive symptoms and the hypothalamic pituitary adrenal axis (HPA axis), few studies have sought to understand the biological pathways through which negative emotionality, depressive symptomatology and cortisol—one of the primary hormonal products of the HPA axis—are associated. The present study explored whether negative emotionality influenced cortisol dysregulation through current depressive symptomatology and whether negative emotionality served as a moderator of the relationship between depressive symptoms and cortisol. In the community-based Vietnam Era Twin Study of Aging, 783 male twins completed two days of cortisol saliva sampling in their natural environments. Three measures of cortisol were analyzed: waking levels, the cortisol awakening response, and the peak to bed slope. Depressive symptoms significantly mediated the associations between negative emotionality and the peak to bed slope. A 2-way interaction between depressive symptoms and negative emotionality was significant for the peak to bed slope and for waking levels of cortisol. Exploration of the interactions illustrated that depressive symptoms only affected cortisol slopes at average or high levels of negative emotionality and only affected waking levels at low levels of negative emotionality. Negative emotionality and depressive symptoms were not related to the cortisol awakening response. This is the first study to find indirect associations between negative emotionality and peak to bed cortisol slopes through depressive symptoms. These findings illustrate the complex interplay between personality characteristics, depressive symptoms and different indices of the cortisol diurnal rhythm.     

Racial and ethnic differences in diurnal cortisol rhythms in preadolescents: the role of parental psychosocial risk and monitoring

Racial/ethnic minorities experience persistent health disparities due in part to their exposure to chronic SES and psychosocial risk. The hypothalamic-pituitary-adrenal axis and its hormonal end product, cortisol, are believed to mediate the associations between chronic stress and poor health. In this study, racial/ethnic differences in diurnal salivary cortisol rhythms in 179 preadolescent youths and the contributing roles of SES risk, psychosocial risk, perceived discrimination, harsh parenting, and parental monitoring were examined. The analyses revealed racial/ethnic differences in diurnal cortisol rhythms, with African Americans having significantly flatter morning-to-evening cortisol slopes than Caucasians and with Latinos having significantly lower evening cortisol levels than Caucasians. Greater psychosocial risk and less parental monitoring were associated with flatter cortisol slopes. Racial/ethnic differences on the cortisol measures persisted when controlling for SES, psychosocial risk, and parenting quality. The need to assess chronic risk across the lifespan and disentangle possible genetic from environmental contributors is discussed.     

Glucose but not protein or fat load amplifies the cortisol response to psychosocial stress

We previously reported that glucose intake amplifies cortisol response to psychosocial stress and smoking in healthy young men, while low blood glucose levels prevented the stress-induced activation of the hypothalamus pituitary adrenal (HPA) axis. However, it remains unknown whether this modulation is specific for glucose load or a more common effect of energy availability. To elucidate this question, 37 healthy men, who fasted for at least 8 h before the experiment, were randomly assigned to four experimental groups, who received glucose (n = 8), protein (n = 10), fat (n = 10), and water (n = 9), one h before their exposure to the Trier Social Stress Test (TSST). Blood glucose levels were measured at baseline and following stress, while salivary cortisol was assessed repeatedly measured before after the TSST. The results show that both absolute cortisol levels and net cortisol increase were greater in the glucose group in comparison to the other groups (F(3,33) = 3.00, P < 0.05 and F(3,33) = 3.08, P < 0.05, respectively. No group differences were observed with respect to perceived stress and mood. Furthermore, the cortisol response was positively correlated with blood glucose changes (r = 0.49, P < 0.002). In conclusion, the results suggest a central mechanism responsible for regulation of energy balance and HPA axis activation, rather than peripheral mechanisms. We thus recommend controlling for blood glucose levels when studying HPA axis responsiveness.     

Genetic and environmental influences on individual differences in cortisol level and circadian rhythm in middle childhood

Individuals differ widely in cortisol output over the day, but the etiology of these individual differences remains poorly understood. Twin studies are useful for quantifying genetic and environmental influences on the variation in cortisol output, lending insight into underlying influences on the components of Hypothalamic-Pituitary-Adrenal (HPA) axis functioning. Salivary cortisol was assayed on 446 twin pairs (157 monozygotic, 289 dizygotic; ages 7-8). Parents helped youth collect saliva 30 min after waking, mid-afternoon, and 30 min prior to bedtime across 3 consecutive days. We used hierarchical linear modeling to extract predicted cortisol levels and to distinguish cortisol's diurnal rhythm using a slopes-as-outcome piecewise growth curve model; two slopes captured the morning-to-afternoon and afternoon-to-evening rhythm, respectively. Separate genetic models were then fit to cortisol level at waking, mid-afternoon, and evening as well as the diurnal rhythm across morning-to-afternoon and afternoon-to-evening hours. Three results from these analyses are striking. First, morning-to-afternoon cortisol level showed the highest additive genetic variance (heritability), consistent with prior research. Second, cortisol's diurnal rhythm had an additive genetic component, particularly across the morning-to-afternoon hours. In contrast, additive genetic variation did not significantly contribute to variation in afternoon-to-evening slope. Third, the majority of variance in cortisol concentration was associated with shared family environments. In summary, both genetic and environmental factors influence cortisol's circadian rhythm, and they do so differentially across the day.     

Sensitivity to stress-induced reproductive dysfunction is associated with a selective but not a generalized increase in activity of the adrenal axis

Stress-induced reproductive dysfunction is a relatively common cause of infertility in women. In response to everyday life stress, some individuals readily develop reproductive dysfunction (i.e., they are stress sensitive), whereas others are more stress resilient. Female cynomolgus monkeys, when exposed to mild combined psychosocial and metabolic stress (change in social environment + 20% reduced calorie diet), can be categorized as stress sensitive (SS; they rapidly become anovulatory in response to stress), medium stress resilient (MSR; they slowly become anovulatory in response to prolonged stress), or highly stress resilient (HSR; they maintain normal menstrual cycles in response to stress). In this study, we examined whether increased sensitivity to stress-induced reproductive dysfunction is associated with elevated adrenal axis activity by measuring 1) the diurnal release of ACTH and cortisol, 2) ACTH and cortisol in response to an acute psychological stress, 3) the percent suppression of cortisol in response to dexamethasone negative feedback, 4) the diurnal release of ACTH and cortisol following exposure to mild psychosocial and metabolic stress, 5) the concentration of cortisol in hair, and 6) adrenal weight. SS monkeys (n = 5) did not differ from MSR (n = 5) or HSR (n = 7) monkeys in any measurement of baseline HPA axis activity or the integrated measurements of chronic HPA axis activity. However, MSR + SS monkeys (n = 10) did secrete more cortisol than HSR monkeys during the daytime hours (1000-1800) following exposure to a novel social environment and reduced diet. We conclude that increased activity of the HPA axis is unlikely to be the primary mechanism causing increased sensitivity to stress-induced reproductive dysfunction.     

Negative relationships in the family-of-origin predict attenuated cortisol in emerging adults

Negative childhood family environments have been associated with stress-related physical and psychological health consequences across the lifespan. The present study examined the relation between adverse relationships in the family of origin and physiological stress response, as measured by salivary cortisol, in emerging adulthood. Seventy-six university students (age range = 18-22) selected from intact married families-of-origin characterized by either negative (n = 39) or positive (n = 37) relationship quality engaged in a challenging role play task. Results from multilevel models indicated that those from negative families exhibited significantly lower salivary cortisol across the task than those from positive families. This relation did not change in strength or direction after controlling for experiences with abuse or recent anxiety or depressive symptoms. These findings suggest the significance of early family relationships on the long-term activity of the HPA axis.     

Do social disadvantage and early family adversity affect the diurnal cortisol rhythm in infants? The Generation R Study

Dysregulation of diurnal cortisol secretion patterns may explain the link between adversities early in life and later mental health problems. However, few studies have investigated the influence of social disadvantage and family adversity on the hypothalamic-pituitary-adrenal (HPA) axis early in life. In 366 infants aged 12-20 months from the Generation R Study, a population-based cohort from fetal life onwards, parents collected saliva samples from their infant at 5 moments over the course of 1 day. The area under the curve (AUC), the cortisol awakening response (CAR) and the diurnal cortisol slope were calculated as different composite measures of the diurnal cortisol rhythm. Information about social disadvantage and early adversity was collected using prenatal and postnatal questionnaires.We found that older infants showed lower AUC levels; moreover, infants with a positive CAR were significantly older. Both the AUC and the CAR were related to indicators of social disadvantage and early adversity. Infants of low income families, in comparison to high income families, showed higher AUC levels and a positive CAR. Infants of mothers who smoked during pregnancy were also significantly more likely to show a positive CAR. Furthermore, infants of mothers experiencing parenting stress showed higher AUC levels. The results of our study show that effects of social disadvantage and early adversity on the diurnal cortisol rhythm are already observable in infants. This may reflect the influence of early negative life events on early maturation of the HPA axis.     

Predicting cortisol stress responses in older individuals: influence of serotonin receptor 1A gene (HTR1A) and stressful life events

Considerable variability in the activity of the hypothalamus-pituitary-adrenal (HPA) axis in response to stress has been found in quantitative genetic studies investigating healthy individuals suggesting that at least part of this variance is due to genetic factors. Since the HPA axis is regulated by a neuronal network including amygdala, hippocampus, prefrontal cortex as well as brainstem circuits, the investigation of candidate genes that impact neurotransmitter systems related to these brain regions might further elucidate the genetic underpinnings of the stress response. However, aside from genetic risk factors, past stressful life events might also result in long-term adjustments of HPA axis reactivity. Here, we investigated the effects of the − 1019 G/C polymorphism in the HTR1A gene encoding the serotonin (5-HT) receptor 1A (5-HT_1A) and stressful life events experienced during childhood and adolescence on changes in cortisol levels in response to the Trier Social Stress Test (TSST) in a sample of healthy older adults (N = 97). Regression analyses revealed a significant effect of HTR1A genotype with the G allele being associated with a less pronounced stress response. In addition, an inverse relationship between past stressful life events and cortisol release but no gene × environment interaction was detected. The results further underscore the crucial role of functional serotonergic genetic variation as well as stressful events during critical stages of development on the acute stress response later in life.     

Is HPA axis reactivity in childhood gender-specific? A systematic review

Background

In adults, hypothalamus–pituitary–adrenal (HPA) axis activity shows sexual dimorphism, and this is thought to be a mechanism underlying sex-specific disease incidence. Evidence is scarce on whether these sex differences are also present in childhood. In a meta-analysis, we recently found that basal (non-stimulated) cortisol in saliva and free cortisol in 24-h urine follow sex-specific patterns. We explored whether these findings could be extended with sex differences in HPA axis reactivity.

Methods

From inception to January 2016, PubMed and EMBASE.com were searched for studies that assessed HPA axis reactivity in healthy girls and boys aged ≤18 years. Articles were systematically assessed and reported in the categories: (1) diurnal rhythm, (2) cortisol awakening response (CAR), (3) protocolled social stress tests similar or equal to the Trier Social Stress Test for children (TSST-C), (4) pharmacological (ACTH and CRH) stress tests, and (5) miscellaneous stress tests.

Results

Two independent assessors selected 109 out of 6158 records for full-text screening, of which 81 studies (with a total of 14,591 subjects) were included. Studies showed that girls had a tendency towards a more variable diurnal rhythm (12 out of 29 studies), a higher CAR (8 out of 18 studies), and a stronger cortisol response to social stress tests (9 out of 21 studies). We found no evidence for sex differences in cortisol response after a pharmacological challenge or to miscellaneous stress tests.

Discussion

Sex differences in HPA axis reactivity appear to be present in childhood, although evidence is not unequivocal. For a better evaluation of sex differences in HPA axis reactivity, standardization of protocols and reports of stress tests is warranted.

     

Rearing condition and plasma cortisol in rhesus monkey infants

Previous studies comparing plasma cortisol levels in mother-reared and nursery-reared rhesus monkey infants under baseline and stress conditions have reported conflicting findings. Differences in subject age, procedures, and specific rearing history may account for many of the discrepant findings. In the present study, mother-reared infants from large social groups, peer-only reared animals, and infants reared with surrogates and limited peer contact were studied in different test conditions across the first 6 months of life. Infants were sampled under three conditions: following a neonatal assessment at Days 14 and 30, immediately upon capture on Day 60, and after 30-min isolation periods on Days 90, 120, and 150. Mother-reared infants exhibited higher cortisol levels on Days 14 and 30 than did both types of nursery-reared infants. In addition, Day 60 basal values of mother-reared infants were higher than those of both peer-reared and surrogate/peer-reared infants. However, on Days 90, 120, and 150, both mother-reared and peer-reared infants exhibited higher cortisol levels in response to separation and 30-min isolation than did the surrogate/peer-reared infants. These differences may reflect group-specific variations in physical environment, capture time, feeding regimen, or diurnal HPA axis rhythms. Am. J. Primatol. 46:311–321, 1998. © 1998 Wiley-Liss, Inc.     

Diurnal cortisol rhythms among Latino immigrants in Oregon, USA

ABSTRACT: One of the most commonly used stress biomarkers is cortisol, a glucocorticoid hormone released by the adrenal glands that is central to the physiological stress response. Free cortisol can be measured in saliva and has been the biomarker of choice in stress studies measuring the function of the hypothalamic-pituitary-adrenal axis. Chronic psychosocial stress can lead to dysregulation of hypothalamic-pituitary-adrenal axis function and result in an abnormal diurnal cortisol profile. Little is known about objectively measured stress and health in Latino populations in the United States, yet this is likely an important factor in understanding health disparities that exist between Latinos and whites. The present study was designed to measure cortisol profiles among Latino immigrant farmworkers in Oregon (USA), and to compare quantitative and qualitative measures of stress in this population. Our results indicate that there were no sex differences in average cortisol AUCg (area under the curve with respect to the ground) over two days (AvgAUCg; males = 1.38, females = 1.60; p = 0.415). AUCg1 (Day 1 AUCg) and AvgAUCg were significantly negatively associated with age in men (p < 0.05). AUCg1 was negatively associated with weight (p < 0.05), waist circumference (p < 0.01) and waist-to-stature ratio (p < 0.05) in women, which is opposite to the expected relationship between cortisol and waist-to-stature ratio, possibly indicating hypothalamic-pituitary-adrenal axis dysregulation. Among men, more time in the United States and immigration to the United States at older ages predicted greater AvgAUCg. Among women, higher lifestyle incongruity was significantly related to greater AvgAUCg. Although preliminary, these results suggest that chronic psychosocial stress plays an important role in health risk in this population. (271 words).     

Long-term effects of early parental loss due to divorce on the HPA axis

We investigated the long-term effects of divorce and early separation from one parent on HPA axis reactivity, in young adults without psychopathology. Participants were 44 young subjects, 22 whose parents divorced before they reached age 10, and 22 controls. Psychiatric symptomatology was measured with the Brief Symptom Inventory (BSI), family perceived stress by the Dyadic Adjustment Scale (DAS), and bonding by the Parental Bonding Instrument (PBI). Assessment of HPA axis function included baseline morning cortisol and ACTH and cortisol response to a CRH stimulation test. No baseline or stimulated group differences were observed for ACTH. Cortisol levels were consistently but insignificantly lower in the divorce group throughout the CRH stimulation reaching statistical significance only at 5 min (p<0.03). Group by time effect reached a trend level (p<0.06). A correlation was found between psychiatric symptomatology and PBI scores; however, both parameters did not correlate with HPA axis activity. A significant correlation was found between DAS scores and ACTH. A regression model revealed a contributing effect for both family stress and child-parent bonding to stimulated ACTH levels. These preliminary findings suggest that even in the absence of adult psychopathology, a history of childhood separation from one parent due to divorce may lead to detectable, albeit mild, long-term alterations in HPA axis activity. Furthermore, they suggest that level of stress at home and parental bonding are important determinants of this effect. It is likely that divorce has significant and sustained effects on children's HPA axis only in the context of a traumatic separation.     

Self-reported symptoms of depressed mood, trait anxiety and aggressive behavior in post-pubertal adolescents: Associations with diurnal cortisol profiles

The association between self-reported symptoms and diurnal cortisol profiles was studied in post-puberty adolescents (29 boys and 29 girls, M_age = 15.06 years). The adolescents completed the Children's Depression Inventory, State Trait Anxiety Inventory, and an Aggressive behavior scale. The diurnal cortisol profile was derived from three saliva samples, collected at awakening, noon and evening on a week-end day. Univariate repeated measurement regressions revealed that depressed mood and trait anxiety were strongly and aggressive behavior was weakly related to the diurnal cortisol profile: greater emotional distress was associated with flatter diurnal cortisol profiles. Multivariate analysis, however, revealed that only trait anxiety made an independent contribution. Further analyses suggested that trait anxiety was related to elevated evening cortisol rather than to decreased awakening cortisol and that from a trait anxiety score of 38 onwards, high anxious adolescents show clearly higher evening cortisol than low anxious adolescents. These data suggest that anxiety disorder co-morbidity might explain some of the differences in HPA-axis function among depressed patients.     

Effects of interpersonal violence-related post-traumatic stress disorder (PTSD) on mother and child diurnal cortisol rhythm and cortisol reactivity to a laboratory stressor involving separation

Women who have experienced interpersonal violence (IPV) are at a higher risk to develop posttraumatic stress disorder (PTSD), with dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and impaired social behavior. Previously, we had reported impaired maternal sensitivity and increased difficulty in identifying emotions (i.e. alexithymia) among IPV-PTSD mothers. One of the aims of the present study was to examine maternal IPV-PTSD salivary cortisol levels diurnally and reactive to their child's distress in relation to maternal alexithymia. Given that mother-child interaction during infancy and early childhood has important long-term consequences on the stress response system, toddlers' cortisol levels were assessed during the day and in response to a laboratory stressor. Mothers collected their own and their 12–48 month-old toddlers' salivary samples at home three times: 30 min after waking up, between 2–3 pm and at bedtime. Moreover, mother-child dyads participated in a 120-min laboratory session, consisting of 3 phases: baseline, stress situation (involving mother-child separation and exposure to novelty) and a 60-min regulation phase. Compared to non-PTSD controls, IPV-PTSD mothers — but not their toddlers, had lower morning cortisol and higher bedtime cortisol levels. As expected, IPV-PTSD mothers and their children showed blunted cortisol reactivity to the laboratory stressor. Maternal cortisol levels were negatively correlated to difficulty in identifying emotions. Our data highlights PTSD-IPV-related alterations in the HPA system and its relevance to maternal behavior. Toddlers of IPV-PTSD mothers also showed an altered pattern of cortisol reactivity to stress that potentially may predispose them to later psychological disorders.     

Disentangling psychobiological mechanisms underlying internalizing and externalizing behaviors in youth: longitudinal and concurrent associations with cortisol

Research examining cortisol dysregulation is seemingly contradictory with studies showing that both internalizing and externalizing behaviors are related to high and low cortisol. One extant theory to explain divergent findings in the stress literature is that both hypo- and hyper-arousal of the hypothalamic-pituitary-adrenal (HPA) axis may be present depending on time since onset of the stressor. This theory may extend to the onset of internalizing and externalizing behaviors. Data from 96 youth participating in a longitudinal project were used to examine this possibility. Composite measures of internalizing and externalizing behaviors at both childhood and early adolescence were formed using mother and teacher reports. Multiple salivary cortisol samples were also collected over two consecutive days during early adolescence. Problematic behaviors were associated with cortisol and the direction of the association was dependent on amount of time passed since onset of the behaviors. When examined concurrently in adolescence, youth with more internalizing behaviors had higher morning cortisol; however, when examined longitudinally, youth with more internalizing behaviors in childhood had lower morning cortisol levels as adolescents. Youth with more externalizing behaviors in childhood had flattened diurnal cortisol rhythms as adolescents, and this finding persisted when examined in adolescence. Cortisol dysregulation was greatest in children with the most severe behavior problems. Findings support the theoretical model of blunting of the HPA axis over time. While the HPA axis may show hyper-arousal when youth first display behaviors, long-term exposure may lead to a hypo-arousal of the HPA axis which culminates in a dysregulated diurnal rhythm.     

Abolished circadian rhythm of salivary cortisol in elite artistic gymnasts

Objective

The aim of this study was to evaluate the effects of intensive physical exercise and acute psychological stress during high level athletic competition as reflected on the levels of salivary cortisol in elite artistic gymnasts (AGs).

Design

The study included 239 AGs (142 females-97 males) who participated in the European Championship of Gymnastics in 2006 and 81 adolescents (40 females-41 males), matched for age, as controls. All athletes participated voluntarily in all or parts of the study, providing samples or data for each of the variables measured. Height, weight, body fat, lean body mass (LBM), bone age and Tanner stage of puberty were assessed and data concerning the time of thelarche, adrenarche and menarche as well as, the onset and the intensity (hours per week) of training were obtained.

Methods

Saliva samples were collected, the morning before training and in the afternoon shortly after the competition. From controls, the saliva samples were collected in the morning. Cortisol concentrations were measured using a chemiluminescence method. Acute stress was assessed using a questionnaire designed for the study.

Results

No difference was found between morning and afternoon salivary cortisol levels in both male and female AGs (females: AM: 15.45 ± 7.45 nmol/l vs PM: 15.73 ± 9.38 nmol/l; males: AM: 10.21 ± 5.52 nmol/l vs PM: 9.93 ± 13.8 nmol/l, p > 0.05).Female AGs presented higher levels of morning salivary cortisol than female controls (p < 0.05). Both male and female AGs had higher degree of psychological stress in comparison with controls (p < 0.001, p < 0.013, respectively). Female AGs had higher morning and afternoon salivary cortisol levels (p < 0.01, p < 0.01, respectively) and higher degree of stress (p < 0.003) than males.

Conclusions

In elite AGs the diurnal rhythm of salivary cortisol has been abolished, probably due to the strenuous training and competition conditions. Female AGs presented higher levels of morning salivary cortisol and psychological stress compared to both male AGs and female controls. The long term consequences of these modifications of the HPA axis remain to be elucidated.