Genetic and environmental influences on cortisol regulation across days and contexts in middle-aged men

Shared community effects and the non-genetic maternal environment shape cortisol levels in wild chimpanzees

Mechanisms of inheritance remain poorly defined for many fitness-mediating traits, especially in long-lived animals with protracted development. Using 6,123 urinary samples from 170 wild chimpanzees, we examined the contributions of genetics, non-genetic maternal effects, and shared community effects on variation in cortisol levels, an established predictor of survival in long-lived primates. Despite evidence for consistent individual variation in cortisol levels across years, between-group effects were more influential and made an overwhelming contribution to variation in this trait. Focusing on within-group variation, non-genetic maternal effects accounted for 8% of the individual differences in average cortisol levels, significantly more than that attributable to genetic factors, which was indistinguishable from zero. These maternal effects are consistent with a primary role of a shared environment in shaping physiology. For chimpanzees, and perhaps other species with long life histories, community and maternal effects appear more relevant than genetic inheritance in shaping key physiological traits.

Indigenous Land-Based Approaches to Well-Being: The Niska (Goose) Harvesting Program in Subarctic Ontario, Canada

Historically, goose harvesting provided a source of culturally significant, safe, and nutritious food for the Omushkego Cree of subarctic Ontario, Canada. Disruptions stemming from colonization and climate change have led to a decrease in harvesting, resulting in higher rates of food insecurity. The aim of the Niska program was to reconnect Elders and youth to revitalize goose harvesting activities and associated Indigenous knowledge within the community. The program and evaluation were built using a two-eyed seeing (Etuaptmumk) and community-based participatory research approach. Salivary cortisol, a biomedical measure of stress, was collected before (n = 13) and after (n = 13) participation in the spring harvest. Likewise, cortisol samples were collected before (n = 12) and after (n = 12) the summer harvest. Photovoice and semi-directed interviews were employed after the spring (n = 13) and summer (n = 12) harvests to identify key elements of well-being from an Indigenous perspective. The changes observed in cortisol levels for the spring (p = 0.782) and summer (p = 0.395) harvests were not statistically significant. However, there was a noteworthy increase in the subjective well-being observed through the qualitative measures (semi-directed interviews and photovoice), highlighting the importance of using multiple perspectives when assessing well-being, especially in Indigenous peoples. Future programs should incorporate multiple perspectives when addressing complex environmental and health issues, such as food security and environmental conservation, especially in Indigenous homelands worldwide.

Does stress predict the development of internalizing symptoms in middle childhood? An examination of additive, mediated, and moderated effects of early family stress, daily interpersonal stress, and physiological stress

Early life stress, daily life experiences, and the stress responsive hypothalamic-pituitary-adrenal (HPA) axis have each been examined as predictors of the development of psychopathology. Rarely have researchers attempted to understand the covariation or interaction among these stress domains using a longitudinal design in the prediction of symptoms of internalizing psychopathology, particularly during childhood. This study examined early family stress, daily interpersonal stress, indicators of diurnal cortisol, and internalizing symptoms in a racially/ethnically and socioeconomically diverse sample of twins (N = 970 children; Mage at outcome = 9.73; 52% female; 23.7% Hispanic/Latino, 58.8% White; 30% below middle class; Lemery-Chalfant et al., 2019). An additive model of stress, a stress mediation model, and a stress sensitization framework model each delineated potential pathways linking stress and internalizing symptoms. Supporting additive pathways, multilevel models showed that all 3 stress indicators uniquely predicted internalizing symptoms. There was a significant indirect path from early family stress to 9 year internalizing symptoms through interpersonal stress, supporting stress mediation. Family stress moderated the association between interpersonal stress and internalizing symptoms, though not in the direction that would support stress sensitization. Child stress, including daily interpersonal stress and HPA axis activity, and internalizing symptoms are prevalent and family stress is a significant precursor to child internalizing symptoms across child development. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Indigenous Land-Based Approaches to Well-Being: The Amisk (Beaver) Harvesting Program in Subarctic Ontario, Canada

The act of decolonizing knowledge systems involves recovering and renewing traditional, non-commodified cultural patterns, such as the sustenance of intergenerational relationships and traditional practices. A decline in beaver harvesting, which was once an integral part of the Omushkego Cree culture, has resulted in an overabundance of beavers and dams, which has negatively affected communities by increasing the local flooding events and impacting the water quality. The aim of the Amisk (beaver) program was to reconnect the Elders and youth to revitalize traditional on-the-land activities and, in the present case, beaver harvesting and associated activities within the community. The program and evaluation were built using a two-eyed seeing (Etuaptmumk) and community-based participatory research approach. Salivary cortisol, a biomedical measure of stress, was collected before and after participation in the program. Photovoice, along with semi-directed interviews, were employed to identify the key elements of well-being from a First Nations’ perspective. For the beaver harvesting activities, the changes observed in the cortisol concentrations were not statistically significant (p = 0.094). However, the act of beaver dam removal was associated with a statistically significant increase in the post-participation cortisol concentration (p = 0.021). It was noteworthy that increased stress during the removal of the beaver dams–as indicated by the elevated post-activity cortisol levels–were not reflected in a decrease in the qualitative measures (semi-directed interviews and photovoice) of well-being from an Indigenous perspective. In fact, there was a noted increase in the subjective well-being of the participants, which highlights the importance of multiple perspectives when assessing well-being, especially in Indigenous peoples. However, the cortisol findings of the present pilot project need to be interpreted with caution, due to the limited sample sizes.

A Prospective Study of Diurnal Cortisol and Incident Dementia in Community-Dwelling Older Adults

Diurnal salivary cortisol was measured in 334 older adults without dementia, at four times on two separate days, under quiet and stressful conditions. In multivariate Cox proportional hazard models, higher global diurnal cortisol secretion was associated with incident dementia (HR = 1.09 [1.02-1.15] per one-unit increase in cortisol measure, p = 0.007) and Alzheimer's disease (HR = 1.12 [1.04-1.21], p = 0.003) over a mean (SD) of 8.1 (4.0) years, independent of potential confounders and stressful conditions. Individuals with incident dementia had a slower rate of cortisol elimination under non-stressful conditions, reflected by higher cortisol levels in the evening, and an abnormal response to stress (blunted evening stress response).

Genetic and environmental influences on cortisol reactivity to a psychosocial stressor in adolescents and young adults

Individuals vary in their response to psychological and physiological stressors, and this reactivity can be captured using measures of cortisol. Previous research suggests cortisol reactivity is under some degree of genetic control; however, the measures used have varied widely. This study (N = 524) examined potential differences in heritability across varying cortisol metrics of stress reactivity following the Trier Social Stress Test (TSST) and whether these measures are genetically or environmentally interrelated. Participants included twins aged 15-20 years (56% female). Cortisol reactivity to the TSST was assessed via serial salivary cortisol samples collected pre- and post-TSST. Modest to moderate heritability estimates (12% [95CI: 1-36%] - 45% [95CI: 16-69%]) were observed across measures purported to capture stress reactivity (peak, area under the curve [AUC], baseline-to-peak change). Findings also demonstrate both shared and unique genetic and environmental influences between baseline cortisol and cortisol reactivity. Minimal to no additional genetic innovations above and beyond the contributions of peak cortisol were found for other measures of cortisol reactivity such as AUC. This study is one of the largest twin-based samples to examine the heritability of cortisol reactivity, and results suggest that simpler measures of cortisol reactivity demonstrate higher heritability compared to more complex measurements.

Genetic parameters of hair cortisol as an indicator of chronic stress under different environments in Holstein cows

Chronic stress is a risk factor for a variety of physiological disorders because of its increased activation of the hypothalamic-pituitary-adrenal (HPA) axis; however, it is difficult to reveal environmental and genetic effects contributing to long-term HPA activity because of the complexity of chronic stress. The hair cortisol concentration (HCC) can be used to reflect the accumulation of HPA axis activity over time. Some studies suggest that the HCC might be associated with the protein concentration (PC) in the hair shaft; however, no studies have revealed a dynamic relationship between them. In the present study, 1,086 hair samples from 418 Holstein cows were collected, and the effects of environmental factors on HCC, PC, and ratio of HCC to PC (HCCP) were studied. Subsequently, regression analysis and curve fitting were used to identify for better-performing indicators of chronic stress. Additionally, univariate and bivariate genetic evaluation were used to estimate the genetic components of cortisol traits and genotype by environment interactions (G × E) under different environmental and physiological states. The results showed that HCC and PC are significantly affected by hair color, sampling year, and season, whereas HCCP is not influenced by hair color. Adjusted PC and HCCP, where confounding effects are excluded, were moderately related with chronic stress indicators. Moderate to high heritabilities were obtained for HCC (0.347 and 0.390 for winter and summer, respectively), PC (0.402 and 0.495 for winter and summer, respectively) and HCCP (0.289 and 0.460 for winter and summer, respectively) when animals in the same season were evaluated. A moderate G × E interaction was detected in this study, as indicated by the low or negative genetic correlation for the same cortisol trait in different environments (e.g. heat stress condition and thermoneutral condition). In conclusion, HCCP is not affected by hair color compared with the other 2 traits; thus, it has potential as an indicator of chronic stress. Hair cortisol traits could monitor stress response process in cattle, as well as provide a better understanding of genetic mechanism for long-term HPA activity.

An inverted U-shaped relationship between cortisol awakening response and same-day error monitoring function in healthy males

The cortisol awakening response (CAR) is thought to provide an energetic "boost" for the coming day and has been shown to be associated with prefrontal dependent function. The aim of the current study was to examine the relationship between the CAR and same-day neural activity following an error response task. Forty-six healthy males (22.25 years ± 1.98) collected saliva samples at 0, 30 and 45 min post-awakening to measure the CAR, and on the same afternoon event-related potential activity during error processing was measured. Although no association was observed between CAR and post-error behavior, a significant quadratic relationship was observed between CAR and Error-related Negativity (ERN) amplitude, and this association remained while controlling for confounding factors. This finding suggested the existence of an inverted U-shaped relationship between CAR and the same-day error-monitoring function in healthy males.

11β-Hydroxylase (CYP11B1) gene variants and new-onset depression in later life

BACKGROUND

Cumulative exposure to high glucocorticoid levels is detrimental for the brain and may have particular implications in later life. A feature of late-life depression is increased cortisol secretion. Variants in the CYP11B1 gene, which codes for the enzyme responsible for cortisol synthesis, could influence risk of late-life depression, but this hypothesis has not been examined. We investigated the associations between variants in the CYP11B1 gene and late-life depression, taking into account history of depression and potential sex-specific effects.

METHODS

We assessed depression in 1007 community-dwellers aged 65 years or older (60% women) at baseline and over a 14-year follow-up. A clinical level of depression was defined as a score of ≥ 16 on the Centre for Epidemiology Studies Depression scale or a diagnosis of current major depression based on the Mini-International Neuropsychiatric Interview and according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). We examined incident and recurrent depression in participants without or with a history of major depression, respectively. We genotyped 5 single-nucleotide polymorphisms (SNPs) spanning CYP11B1. We used multivariable analyses to adjust for age, body mass index, cardiovascular ischemic pathologies, hypertension, cognitive impairment and anxiety.

RESULTS

In women, rs6471580 and rs7016924 were associated with a 50% lower rate of incident (new-onset) late-life depression, and rs11783855 was associated with a 2.4-fold higher rate of late-life depression. These associations remained after correction for multiple testing, but we found no associations for recurrent depression in women or men.

LIMITATIONS

This study focused on the major gene involved in corticosteroid biosynthesis, but other genes may also be implicated in this pathway.

CONCLUSION

Variants of the CYP11B1 gene appear to be susceptibility factors for late-life depression in a sex-specific manner.

Stress & executive functioning: A review considering moderating factors

A multitude of studies investigating the effects of stress on cognition has produced an inconsistent picture on whether - and under which conditions - stress has advantageous or disadvantageous effects on executive functions (EF). This review provides a short introduction to the concept of stress and its neurobiology, before discussing the need to consider moderating factors in the association between stress and EF. Three core domains are described and discussed in relation to the interplay between stress and cognition: the influence of different paradigms on physiological stress reactivity, individual differences in demographic and biological factors, and task-related features of cognitive tasks. Although some moderating variables such as the endocrine stress response have frequently been considered in single studies, no attempt of a holistic overview has been made so far. Therefore, we propose a more nuanced and systematic framework to study the effects of stress on executive functioning, comprising a holistic overview from the induction of stress, via biological mechanisms and interactions with individual differences, to the influence of stress on cognitive performance.

Heritability of Cortisol Production and Metabolism Throughout Adolescence

CONTEXT

Inter-individual differences in cortisol production and metabolism emerge with age and may be explained by genetic factors.

OBJECTIVE

To estimate the relative contributions of genetic and environmental factors to inter-individual differences in cortisol production and metabolism throughout adolescence.

DESIGN

Prospective follow-up study of twins.

SETTING

Nationwide register.

PARTICIPANTS

218 mono- and dizygotic twins (N = 109 pairs) born between 1995 amd 1996, recruited from the Netherlands Twin Register. Cortisol metabolites were determined in 213, 169, and 160 urine samples at the ages of 9, 12, and 17, respectively.

MAIN OUTCOME MEASURES

The total contribution of genetic factors (broad-sense heritability) and shared and unshared environmental influences to inter-individual differences in cortisol production and activities of 5α-reductase, 5β-reductase, and 11β-hydroxysteroid dehydrogenases and cytochrome P450 3A4.

RESULTS

For cortisol production rate at the ages of 9, 12, and 17, broad-sense heritability was estimated as 42%, 30%, and 0%, respectively, and the remainder of the variance was explained by unshared environmental factors. For cortisol metabolism indices, the following heritability was observed: for the A-ring reductases (5α-and 5β-reductases), broad-sense heritability increased with age (to >50%), while for the other indices (renal 11β-HSD2, global 11β-HSD, and CYP3A4), the contribution of genetic factors was highest (68%, 18%, and 67%, respectively) at age 12.

CONCLUSIONS

The contribution of genetic factors to inter-individual differences in cortisol production decreased between 12 and 17y, indicative of a predominant role of individual circumstances. For cortisol metabolism, distinct patterns of genetic and environmental influences were observed, with heritability that either increased with age or peaked at age 12y.

Current Status of the Vietnam Era Twin Study of Aging (VETSA)

The Vietnam Era Twin Study of Aging (VETSA) is a longitudinal behavioral genetic study with a primary focus on cognitive and brain aging in men, particularly early identification of risk for mild cognitive impairment (MCI) and Alzheimer's disease (AD). It comprises a subset of over 1600 twins from the Vietnam Era Twin Registry. Twins live all over the USA. Assessments began when participants were in their 50s. Follow-ups were conducted every 5-6 years, and wave 3 has been completed as of this writing. The age range of participants is narrow (about 10 years). An extensive neurocognitive test battery has added precision in assessing differences in middle-aged adults, and predicting progression to MCI. Young adult cognitive test data (at an average age of 20 years) provide a means of disentangling aging effects from longstanding differences. Genome wide genotyping and plasma assays of AD biomarkers from waves 1 and 3 were conducted in wave 3. These features make the VETSA ideal for studying the heterogeneity of within-individual trajectories from midlife to old age, and for early detection of risk factors for cognitive decline.

Mother-child adrenocortical synchrony: Roles of maternal overcontrol and child developmental phase

An increasing amount of empirical attention is focused on adrenocortical synchrony as an index of biobehavioral co-regulation between parent and child in the context of early child development. Working with an ethnically diverse community sample of children (N = 99, 50.5% male, ages 9-12), we collected saliva samples from mother-child dyads prior to and after a laboratory-based performance challenge task, and tested whether maternal overcontrol and child age moderated dyadic synchrony in cortisol. Results revealed that cortisol levels between mothers and children were significantly positively correlated at pretask for dyads with mean age and older children only, at 25-min post-task for all dyads, and at 45-min post-task for all dyads. Higher overcontrol/older child dyads exhibited a unique pattern of cortisol synchrony wherein at pretask, mother-child levels had the strongest positive correlation, whereas at 25 and 45 min, mother-child cortisol levels were significantly inversely correlated. These findings contribute to theory and research on parent-child relationships by examining parenting behavior, developmental stage, and adrenocortical synchrony in tandem.

Interactive effects of testosterone and cortisol on hippocampal volume and episodic memory in middle-aged men

Animal and human research suggests that testosterone is associated with hippocampal structure and function. Studies examining the association between testosterone and either hippocampal structure or hippocampal-mediated cognitive processes have overwhelmingly focused on the effects of testosterone alone, without considering the interaction of other neuroendocrine factors. The aim of the present study was to examine the interactive effects of testosterone and cortisol in relation to hippocampal volume and episodic memory in a sample of late-middle aged men from the Vietnam Era Twin Study of Aging. The average age of participants was 56.3 years (range 51-60). Salivary hormone samples were collected at multiple time-points on two non-consecutive at-home days, and an in-lab assessment. Area under the curve with respect to ground measures for cortisol and testosterone were utilized. Significant testosterone-by-cortisol interactions were observed for hippocampal volume, and episodic memory. When cortisol levels were elevated (1 SD above the mean), testosterone levels were positively associated with hippocampal volume and memory performance. However, when cortisol levels were low (1 SD below the mean), testosterone levels were inversely related to hippocampal volume and memory performance. These findings suggest that in context of high cortisol levels, testosterone may be neuroprotective. In contrast, low testosterone may also be neuroprotective in the context of low cortisol levels. To our knowledge this is the first demonstration of such an interaction in a structural brain measure and an associated cognitive ability. These results argue in favor of broadening neuroendocrine research to consider the simultaneous and interactive effects of multiple hormones on brain structure and function.

The effect of an adverse psychological environment on salivary cortisol levels in the elderly differs by 5-HTTLPR genotype

BACKGROUND

An adverse psychological environment (e.g. stressful events or depression) has been shown to influence basal cortisol levels and cortisol response to stress. This differs depending on the adverse stimuli, but also varies across individuals and may be influenced by genetic predisposition. An insertion/deletion polymorphism in the serotonin transporter gene (5-HTTLPR) is a strong candidate in this regard.

OBJECTIVE

To investigate how stressful life events and depression are associated with diurnal cortisol levels in community-dwelling elderly and determine whether this varies according to genetic variability in the 5-HTTLPR.

METHODS

This population-based study included 334 subjects aged 65 and older (mean (SD) = 76.5 (6.3)). Diurnal cortisol was measured on two separate days, under quiet (basal) and stressful conditions. The number of recent major stressful events experienced during the past year was assessed from a 12-item validated questionnaire as an index of cumulative recent stressful events. Lifetime trauma was evaluated using the validated Watson's PTSD inventory, which evaluates the most severe traumatic or frightening experience according to DSM criteria. Depression was defined as having a Mini-International Neuropsychiatric Interview (MINI) diagnosis of current major depressive disorder or high levels of depressive symptoms (Center for Epidemiologic Studies-Depression Scale ≥16). 5-HTTLPR genotyping was performed on blood samples.

RESULTS

Exposure to stressful life events was associated with lower basal evening cortisol levels overall, and in the participants with the 5-HTTLPR L allele but not the SS genotype. The greatest effects (over 50% decrease, p < 0.001) were observed for the LL participants having experienced multiple recent stressful events or severe lifetime traumas. Participants with the L allele also had higher evening cortisol stress response. Conversely, depression tended to be associated with a 42% higher basal morning cortisol in the SS participants specifically, but did not modify the association between stressful events and cortisol levels.

CONCLUSION

An adverse psychological environment is associated with basal cortisol levels and cortisol stress response, but this differs according to 5-HTTLPR genotype.

Physiologic and Psychologic Risk Factors in Central Serous Chorioretinopathy

PURPOSE

Central serous chorioretinopathy (CSCR) is characterized by macular detachment due to thickened choroid, mostly affecting young men under perceived stress. Although most previous studies on CSCR have been retrospective and have focused on a single facet of the patient's personality, we conducted a prospective, intercontinental, controlled study to analyze the multifaceted personality profile in CSCR.

DESIGN

Prospective, cross-sectional, case-control study.

PARTICIPANTS

Subjects with CSCR from 6 university-based eye clinics consented to participate in a questionnaire. Controls without retinal disease were recruited from the same clinics.

METHODS

The interview consisted of a 60-item questionnaire. Recruitment of participants was from January 2015 to February 2016. Controls were matched for age, gender, and race. Statistical analyses were performed using univariate and multivariate analyses.

MAIN OUTCOME MEASURES

The main parameters registered were presence of stress, daily number of cups caffeine intake, and personality traits (Type A; obsessive-compulsive; aggressive).

RESULTS

A total of 83 consecutive patients with CSCR (mean age, 45.9 years; male, 80.7%) and 83 controls (mean age, 46.0 years; male, 80.7%) were analyzed for 60 variables. Multivariate analysis revealed a strong association with obsessive-compulsive behavior (P = 0.001), caffeine intake (P = 0.002), Type A personality (P = 0.002), continuous stress (P = 0.001), and premature ejaculation (P = 0.001).

CONCLUSIONS

This study sheds light on the unique psychologic functioning of patients with CSCR: preoccupied, inflexible, perfectionist (obsessive-compulsive tendency), competitive, ambitious, impatient, high achiever (Type A personality), and under continuous stress. In addition, caffeine abuse and premature ejaculation were linked to CSCR.

The genetics of anxiety-related negative valence system traits

NIMH's Research Domain Criteria (RDoC) domain of negative valence systems (NVS) captures constructs of negative affect such as fear and distress traditionally subsumed under the various internalizing disorders. Through its aims to capture dimensional measures that cut across diagnostic categories and are linked to underlying neurobiological systems, a large number of phenotypic constructs have been proposed as potential research targets. Since "genes" represent a central "unit of analysis" in the RDoC matrix, it is important for studies going forward to apply what is known about the genetics of these phenotypes as well as fill in the gaps of existing knowledge. This article reviews the extant genetic epidemiological data (twin studies, heritability) and molecular genetic association findings for a broad range of putative NVS phenotypic measures. We find that scant genetic epidemiological data is available for experimentally derived measures such as attentional bias, peripheral physiology, or brain-based measures of threat response. The molecular genetic basis of NVS phenotypes is in its infancy, since most studies have focused on a small number of candidate genes selected for putative association to anxiety disorders (ADs). Thus, more research is required to provide a firm understanding of the genetic aspects of anxiety-related NVS constructs. © 2016 Wiley Periodicals, Inc.

Heterogeneity in HPA axis dysregulation and serotonergic vulnerability to depression

Variability in the serotonin transporter (5-HTTLPR) gene can influence the risk of depression associated with adversity, as well as cortisol stress reactivity, although not consistently. No study has examined the impact of both a stressful environment and corticotropic-axis dysfunction on depression, as a function of 5-HTTLPR. This population-based study included 334 subjects aged 65 and older. Depression was measured at both diagnostic (major depression according to DSM-IV) and symptomatic (subthreshold depression) levels of caseness, in addition to 5-HTTLPR and rs25531 genotyping and diurnal cortisol measures. For participants with the SS genotype, higher morning cortisol levels were associated with a 4-fold increased risk of depression. Among LL participants, both evening cortisol levels and recent stressful events increased depression risk, although only the latter remained significant after multivariable adjustment. Conversely, SL individuals appeared somewhat resilient to depression in terms of cortisol and recent stress. These findings indicate that 5-HTTLPR genetic variability appears to influence the association between stress-related factors and late-life depression, although the gene-environment interactions failed to reach statistical significance levels. Participants homozygous for the short allele appeared to have a cortisol-related neuroendocrine vulnerability to depression, while long allele homozygotes were more reactive to stressful events in terms of depression risk.

Cortisol Awakening Response and Acute Stress Reactivity in First Nations People

First Nations people globally have a higher incidence of mental disorders and non-communicable diseases. These health inequalities are partially attributed to a complex network of social and environmental factors which likely converge on chronic psychosocial stress. We hypothesized that alterations in stress processing and the regulation of the hypothalamic-pituitary-adrenal axis might underlie health disparities in First Nations people. We assessed the cortisol awakening response and the dynamic response to a laboratory induced psychosocial stress of young Indigenous tertiary students (n = 11, mean age 23.82 years) and non-Indigenous students (n = 11) matched for age and gender. Indigenous participants had a blunted cortisol awakening response (27.40 (SD 35.00) vs. 95.24 (SD 55.23), p = 0.002), which was differentially associated with chronic experience of stress in Indigenous (r = -0.641, p = 0.046) and non-Indigenous (r = 0.652, p = 0.03) participants. The cortisol response to the laboratory induced psychosocial stress did not differ between groups. Self-reported racial discrimination was strongly associated with flattened cortisol response to stress (r = -0676, p = 0.022) and with heart rate variability (r = 0.654, p = 0.040). Our findings provide insight into potential biological factors underlying health discrepancies in ethnic minority groups.

The cortisol awakening response and cognition across the adult lifespan

Although the hippocampus is thought to play a central role in the regulation of the cortisol awakening response (CAR), results from past studies examining the relationship between the CAR and hippocampal-mediated memory and cognition have been mixed. Inconsistent findings may be due to the use of cortisol samples collected on only 1-2days since reduced sampling can permit unstable situational factors to bias results. We used cortisol assessments from 10 consecutive days to test the relationship of the CAR to episodic memory, working memory, and processing speed in a sample of healthy young, middle-aged, and older adults (age range: 23-79years; N=56). We tested if the relationship between the CAR and cognition would depend upon age and also tested if other cortisol measures, specifically waking cortisol, diurnal cortisol output (i.e., area under the curve) and diurnal cortisol slope (linear and quadratic), would be related to cognition. We found that a more positive CAR slope was related to better episodic memory and that this relationship did not depend upon age. The CAR was not significantly related to working memory. The relationship of the CAR to processing speed was not significant when using a CAR measure that corrected for non-compliant cortisol sampling. We also found that higher waking cortisol was significantly related to better working memory, but not episodic memory or processing speed. Neither diurnal cortisol output nor diurnal linear cortisol slope was significantly related to cognitive functioning. Future work should investigate the mechanisms underpinning the relationship of the cortisol awakening process to cognitive functioning.

Evidence of a unique and common genetic etiology between the CAR and the remaining part of the diurnal cycle: A study of 14 year-old twins

INTRODUCTION

By and large, studies have reported moderate contributions of genetic factors to cortisol secreted in the early morning and even smaller estimates later in the day. In contrast, the cortisol awakening response (CAR) has shown much stronger heritability estimates, which prompted the hypothesis that the etiology of cortisol secretion may vary according to the time of day. A direct test of this possibility has, however, not yet been performed.

OBJECTIVE

To describe the specific and common etiology of the CAR, awakening level and cortisol change from morning to evening in an age-homogenous sample of twin adolescents.

METHODS

A total of 592 participants of the Québec Newborn Twin Study, a population-based 1995-1998 cohort of families with twins in Canada, have collected saliva at awakening, 30 min later, at the end of afternoon and in the evening over four collection days.

RESULTS

Multivariate Cholesky models showed both specific and common sources of variance between the CAR, awakening and cortisol diurnal change. The CAR had the strongest heritability estimates, which, for the most part, did not overlap with the other indicators. Conversely, similar magnitudes of genetic and environmental contributions were detected at awakening and for diurnal change, which partially overlapped.

CONCLUSION

Our study unraveled differences between the latent etiologies of the CAR and the rest of the diurnal cycle, which may contribute to identify regulatory genes and environments and detangle how these indicators each relate to physical and mental health.

Stress at work: Differential experiences of high versus low SES workers

This paper asks whether workers with higher socioeconomic status (SES) experience different levels of stress at work than workers with lower SES and, if so, what might explain these differences. We collected innovative assessments of immediate objective and subjective measures of stress at multiple time points across consecutive days from 122 employed men and women. We find that in comparison to higher SES individuals, those with lower SES reported greater happiness at work, less self-reported stress, and less perceived stress; cortisol, a biological marker of stress, was unrelated to SES. Worker's momentary perceptions of the workplace were predicted by SES, with higher SES individuals more commonly reporting feeling unable to meet work demands, fewer work resources, and less positive work appraisals. In turn, perceptions of the workplace had a generally consistent and robust effect on positive mood, subjective stress, and cortisol.

Genetic Moderation of Stress Effects on Corticolimbic Circuitry

Stress exposure is associated with individual differences in corticolimbic structure and function that often mirror patterns observed in psychopathology. Gene x environment interaction research suggests that genetic variation moderates the impact of stress on risk for psychopathology. On the basis of these findings, imaging genetics, which attempts to link variability in DNA sequence and structure to neural phenotypes, has begun to incorporate measures of the environment. This research paradigm, known as imaging gene x environment interaction (iGxE), is beginning to contribute to our understanding of the neural mechanisms through which genetic variation and stress increase psychopathology risk. Although awaiting replication, evidence suggests that genetic variation within the canonical neuroendocrine stress hormone system, the hypothalamic-pituitary-adrenal axis, contributes to variability in stress-related corticolimbic structure and function, which, in turn, confers risk for psychopathology. For iGxE research to reach its full potential it will have to address many challenges, of which we discuss: (i) small effects, (ii) measuring the environment and neural phenotypes, (iii) the absence of detailed mechanisms, and (iv) incorporating development. By actively addressing these challenges, iGxE research is poised to help identify the neural mechanisms underlying genetic and environmental associations with psychopathology.

Concordance of mother-daughter diurnal cortisol production: Understanding the intergenerational transmission of risk for depression

A growing body of research is demonstrating concordance between mother and child diurnal cortisol production. In the context of maternal history of depression, intergenerational concordance of cortisol production could contribute to hypercortisolemia in children of depressed mothers, which has been shown to increase risk for MDD. The current study is the first to examine concordance in diurnal cortisol production between mothers with a history of depression and their never-depressed, but high-risk, children. We collected salivary cortisol across 2 days from mothers with (remitted; RMD) and without (CTL) a history of recurrent episodes of depression and their never-depressed daughters. As expected, RMD mothers and their daughters both exhibited higher cortisol production than did their CTL counterparts. Moreover, both across and within groups, mothers' and daughters' cortisol production were directly coupled. These findings suggest that there is an intergenerational concordance in cortisol dysregulation that may contribute to hypercortisolemia in girls at familial risk for depression.

Sleep- and circadian rhythm-associated pathways as therapeutic targets in bipolar disorder

INTRODUCTION

Disruptions in sleep and circadian rhythms are observed in individuals with bipolar disorders (BD), both during acute mood episodes and remission. Such abnormalities may relate to dysfunction of the molecular circadian clock and could offer a target for new drugs.

AREAS COVERED

This review focuses on clinical, actigraphic, biochemical and genetic biomarkers of BDs, as well as animal and cellular models, and highlights that sleep and circadian rhythm disturbances are closely linked to the susceptibility to BDs and vulnerability to mood relapses. As lithium is likely to act as a synchronizer and stabilizer of circadian rhythms, we will review pharmacogenetic studies testing circadian gene polymorphisms and prophylactic response to lithium. Interventions such as sleep deprivation, light therapy and psychological therapies may also target sleep and circadian disruptions in BDs efficiently for treatment and prevention of bipolar depression.

EXPERT OPINION

We suggest that future research should clarify the associations between sleep and circadian rhythm disturbances and alterations of the molecular clock in order to identify critical targets within the circadian pathway. The investigation of such targets using human cellular models or animal models combined with 'omics' approaches are crucial steps for new drug development.

The cortisol awakening response and major depression: examining the evidence

A vast body of literature has revealed that dysregulation of the hypothalamic-pituitary-adrenal (HPA) stress axis is associated with etiology of major depressive disorder (MDD). There are many ways that the dysregulation of the HPA axis can be assessed: by sampling diurnal basal secretion and/or in response to a stress task, pharmacological challenge, and awakening. Here, we focus on the association between cortisol awakening response (CAR), as one index of HPA axis function, and MDD, given that the nature of this association is particularly unclear. Indeed, in the following selective review, we attempt to reconcile sometimes-divergent evidence of the role of CAR in the pathway to depression. We first examine association of CAR with psychological factors that have been linked with increased vulnerability to develop depression. Then, we summarize the findings regarding the CAR profile in those with current depression, and evaluate evidence for the role of CAR following depression resolution and continued vulnerability. Finally, we showcase longitudinal studies showing the role of CAR in predicting depression onset and recurrence. Overall, the studies reveal an important, but complex, association between CAR and vulnerability to depression.

Interaction of APOE genotype and testosterone on episodic memory in middle-aged men

Age-related changes in testosterone are believed to be a key component of the processes that contribute to cognitive aging in men. The APOE-ε4 allele may interact with testosterone and moderate the hormone's association with cognition. The goals of the present study were to examine the degree to which free testosterone is associated with episodic memory in a community-based sample of middle-aged men, and examine the potential interaction between free testosterone and the APOE-ε4 allele. Data were used from 717 participants in the Vietnam Era Twin Study of Aging. Average age was 55.4 years (standard deviation = 2.5). Significant positive associations were observed between free testosterone level and verbal episodic memory, as well as a significant interaction between free testosterone and APOE-ε4 status. In ε4 carriers free testosterone was positively associated with verbal episodic memory performance (story recall), whereas no association was observed in ε4 noncarriers. Results support the hypothesis that APOE-ε4 status increases susceptibility to other risk factors, such as low testosterone, which may ultimately contribute to cognitive decline or dementia.

Genetic and environmental influences of daily and intra-individual variation in testosterone levels in middle-aged men

BACKGROUND

Testosterone regulates numerous physiological processes, and evidence suggests that it plays a critical role in male aging. It has yet to be determined whether the heritability of testosterone varies in accordance with its diurnal rhythm. Similarly, it is unclear whether changes in testosterone level throughout the day are genetically influenced. The aim of the present study was to determine the degree to which genetic and environmental factors contribute to individual differences in testosterone throughout the day in middle-aged men.

METHODS

Saliva-based measures of free testosterone, sampled at multiple time-points both at-home and in-lab, were collected from 783 male twins (193 monozygotic pairs, 196 dizygotic pairs, 5 unpaired twins) as part of the Vietnam Era Twin Study of Aging (VETSA). The average age of participants was 55.9 years (SD=2.6).

RESULTS

Testosterone levels declined substantially over the course of the day, with 32-39% of the change occurring in the first 30min after waking. Heritability estimates for specific time-points ranged from .02 to .39. The heritability of the average at-home and in-lab testosterone values were notably higher (.42 and .47 respectively). Daily rates of change showed some evidence of genetic influence, with heritability estimates ranging from .15 to .29, whereas there were no observable genetic influences on coefficients of variation.

CONCLUSIONS

Genetic influences account for a significant proportion of the variance in average testosterone levels, while environmental factors account for the majority of intra-individual variability. These results highlight the need to explore both genetic and individual-specific environmental factors as determinants of free testosterone levels in aging men.

Adult cognitive ability and socioeconomic status as mediators of the effects of childhood disadvantage on salivary cortisol in aging adults

In this longitudinal study we investigate the influence of childhood disadvantage on midlife hypothalamic-pituitary-adrenal (HPA) axis regulation. Two mechanisms by which early life stress may affect later pathophysiology are through its influence on cognitive functioning or later socioeconomic (SES) disadvantage. We predicted that individual differences in young adult cognitive ability and midlife SES would mediate the influence of childhood disadvantage on midlife cortisol. On each of three nonconsecutive days, participants provided five salivary cortisol samples corresponding to their diurnal rhythm (N=727 men; mean age 55, SD=2.6). We calculated three measures of cortisol regulation (area-under-the curve cortisol reflecting total daytime cortisol output; cortisol-awakening-response; and wake-to-bed slope), averaging scores for each measure across multiple days. Childhood disadvantage combined four dichotomous indicators used previously by Rutter (1985): father low SES; mother education less than 12th grade; major family disruption/separation before age 18; and large family size (more than 5 siblings). The two mediators were a measure of general cognitive ability assessed at age 20 and highest achieved midlife SES. Men from more disadvantaged childhoods were significantly more likely to have dysregulated cortisol at midlife, with higher daytime cortisol levels decades after their childhood experience. Effects of childhood disadvantage were both direct and indirect. Cognitive ability and adult SES, however, only partially mediated the associations between early life stress and midlife cortisol. Specific indirect effects accounted for 33.8% of the total effect of childhood disadvantage [β=0.12 (0.05; 0.18)] on total daytime cortisol. Associations remained significant after accounting for ethnicity, smoking status, and self-reported depressive symptoms.

Endocrine and immunological parameters in individuals involved in Prestige spill cleanup tasks seven years after the exposure

In November 2002 the oil tanker Prestige spilled 63,000tonnes of heavy oil off the northwest coast of Spain, impacting more than 1000km of coastline. A general concern led to a huge mobilization of human and technical resources, and more than 300,000 people participated in cleanup activities, which lasted up to 10months. Some endocrine and immunological alterations were reported in Prestige oil exposed subjects for several months. Therefore, the objective of this study was to evaluate if these alterations are still present seven years after the exposure. Fifty-four individuals exposed for at least 2months were compared to 50 matched referents. Prolactin and cortisol plasma concentrations, percentages of lymphocyte subsets (CD3(+), CD4(+), CD8(+), CD19(+), and CD56(+)16(+)), plasma levels of circulating cytokines (interleukin (IL) 2, IL4, IL6, IL10, tumour necrosis factor α, and interferon γ), and serum concentrations of neopterin, tryptophan and kynurenine were determined in peripheral blood samples. Results showed significant differences in exposed individuals vs. referents only in cortisol (increase), kynurenine and %CD16(+)56(+) lymphocytes (both decrease). Time of exposure to the oil or using protective clothes did not influence the results, but effect of using protective mask was observed on neopterin, %CD8(+), CD4(+)/CD8(+) ratio and IL4. Surveillance of the exposed individuals for early detection of possible health problems related to the endocrine or immunological systems is recommended.

VETSA: the Vietnam Era Twin Study of Aging

The Vietnam Era Twin Study of Aging (VETSA) is a longitudinal behavioral genetic study with a primary focus on cognitive and brain aging in men. It comprises a subset of over 1,200 twins from the Vietnam Era Twin Registry. Like many other studies of aging, the VETSA includes many different phenotypes, but there are some key features that distinguish it from most other behavioral genetic aging studies. First, the initial assessment was conducted when all participants were middle-aged. Second, the age range of participants is narrow; all were in their 50s at the time of the initial recruitment. Third, the study includes an extensive and demanding neurocognitive test battery that was designed to provide good coverage of different cognitive abilities and avoid ceiling effects in middle-aged adults. Fourth, young adult cognitive test data (at an average age of 20 years) are available to provide a gauge of cognitive change. These features make the VETSA ideal for studying the heterogeneity of within-individual trajectories from midlife to old age, and for early detection of risk factors for cognitive decline.

Molecular genetics of the adrenocortical axis and breeding for robustness

The concept of robustness refers to the combination of a high production potential and a low sensitivity to environmental perturbations. The importance of robustness-related traits in breeding objectives is progressively increasing toward the production of animals with a high production level in a wide range of climatic conditions and production systems, together with a high level of animal welfare. Current strategies to increase robustness include selection for "functional traits," such as skeletal and cardiovascular integrity, disease resistance, and mortality at various stages. It is also possible to use global evaluation of sensitivity to the environment (eg reaction norm analysis or canalization), but these techniques are difficult to implement in practice. The glucocorticoid hormones released by the adrenal cortex exert a wide range of effects on metabolism, the cardiovascular system, inflammatory processes, and brain function, for example. Protein catabolism toward energy production and storage (lipids and glycogen) supports their pivotal role in stress responses aiming at the adaptation and survival of individuals under strong environmental pressure. Large individual variations have been described in adrenocortical axis activity, with important physiopathological consequences. In terms of animal production, higher cortisol levels have negative effects on growth rate and feed efficiency and increase the fat:lean ratio of carcasses. On the contrary, cortisol has positive effects on functional traits and adaptation. Intense selection for lean tissue growth and more generally high protein output during the past decades has concomitantly reduced cortisol production, which may be responsible for the negative effects of selection on functional traits. In this paper, we review experimental evidence suggesting that the balance between production and functional traits was modified in favor of improved robustness by selecting animals with higher adrenocortical axis activity, as well as the molecular genetic tools that can be used to fine-tune this objective.

The Stockholm Neonatal Family-Centered Care Study: effects on salivary cortisol in infants and their mothers

BACKGROUND

Parental involvement in the care of preterm infants in neonatal intensive care units (NICUs) is common, but little is known about the effect on stress responses in mothers and infants.

AIMS

The aim of this study is to evaluate the effect of family-centered care on salivary cortisol reactivity in mothers and preterm infants and the correlation between the mothers' and the preterm infants' salivary cortisol levels.

METHODS

This study is part of a randomized controlled trial conducted at two level-II NICUs, including Family Care (FC), where parents were able to stay 24h/day from admission to discharge, and Standard Care (SC). To investigate the cortisol response, saliva was collected from 289 preterm infants and their mothers before and after a diaper change at the time of discharge.

RESULTS

No significant differences were found between the two groups in salivary cortisol reactivity, either in mothers or in infants. The results revealed a correlation between preterm infants' and their mothers' baseline and response cortisol in the FC group: r=0.31 (p=0.001) and r=0.24 (p=0.01), respectively. Such correlation was not observed in the SC group: r=0.14 (p=0.14) and r=0.18 (p=0.07), respectively.

CONCLUSIONS

Family-centered care had no effect on salivary cortisol reactivity during diaper change. However, sharing the same environment may increase the concordance between preterm infants' and their mothers' salivary cortisol levels.

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.

The heritability of brain metabolites on proton magnetic resonance spectroscopy in older individuals

Twin studies have shown that many aspects of brain structure are heritable, suggesting a strong genetic contribution to brain structure. Less is known about functional aspects of the brain, in particular biologically relevant metabolites in the brain such as those measured by proton magnetic resonance spectroscopy (((1))H MRS), N-acetyl-aspartate (NAA), creatine (Cr), choline (Cho) and myoinositol (ml), which have been suggested as possible markers of brain aging and early dementia. We examined 296 (56 male/108 female monozygotic and 43 male/89 female dizygotic) older twins (mean age 72.2 ± 5.5 years, range 65-88), for the levels of these metabolites relative to the H(2)O signal in the posterior cingulate cortex using ((1))H MRS. All metabolites showed substantial heritability, which was greatest for the neuronal integrity marker NAA (72%), and less so for the others - Cr (51%), Cho (33%) and ml (55%). The heritability of these markers did not change significantly with age or sex. The genetic determination of NAA, along with the evidence that NAA levels change in aging and neurodegenerative diseases suggest that it is a potential endophenotype of brain aging and dementia.

Genetic and environmental effects on diurnal dehydroepiandrosterone sulfate concentrations in middle-aged men

BACKGROUND

Dehydroepiandrosterone sulfate (DHEAS) is important for its association with immune system function and health outcomes. The characterization of the genetic and environmental contributions to daily DHEAS concentrations is thus important for understanding the genetics of health and aging.

METHODS

Saliva was collected from 783 middle-aged men (389 complete pairs and 5 unpaired twins) as part of the Vietnam Era Twin Study of Aging. Samples were taken at multiple specified time points across two non-consecutive days in the home and one day at the study sites. A twin modeling approach was used to estimate genetic and environmental contributions for time-specific and average DHEAS concentrations.

RESULTS

There was a consistent diurnal pattern for DHEAS concentrations in both at-home and day-of-testing (DOT) measures, which was the highest at awakening and decreased slightly throughout the day. Heritability estimates were significant for measures at 10 am, 3 pm and bedtime for the in-home days and at 10 am and 3 pm on the DOT, ranging between 0.37 and 0.46.

CONCLUSIONS

The significant heritability estimates later in the day reflect time-specific genetic effects for DHEAS, compared with prior twin and family designs studies which frequently used averaged morning-only measures. Additive genetic influences on DHEAS concentrations were consistent between at-home and DOT measures.

Heritability and genetic correlation of hair cortisol in vervet monkeys in low and higher stress environments

Chronic activation of the hypothalamic-pituitary adrenal (HPA) system is a risk factor for a variety of physical and mental disorders, and yet the complexity of the system has made it difficult to define the role of genetic and environmental factors in producing long-term individual differences in HPA activity. Cortisol levels in hair have been suggested as a marker of total HPA activation over a period of several months. This study takes advantage of a pedigreed nonhuman primate colony to investigate genetic and environmental influences on hair cortisol levels before and after an environmental change. A sample of 226 adult female vervet monkeys (age 3-18) living in multigenerational, matrilineal social groups at the Vervet Research Colony were sampled in a stable low stress baseline environment and 6 months after the entire colony was moved to a new facility with more frequent handling and group disturbances (higher stress environment). Variance components analysis using the extended colony pedigree was applied to determine heritability of hair cortisol levels in the two environments. Bivariate genetic correlation assessed degree of overlap in genes influencing hair cortisol levels in the low and higher stress environments. The results showed that levels of cortisol in hair of female vervets increased significantly from the baseline to the post-move environment. Hair cortisol levels were heritable in both environments (h(2)=0.31), and there was a high genetic correlation across environments (rhoG=0.79), indicating substantial overlap in the genes affecting HPA activity in low and higher stress environments. This is the first study to demonstrate that the level of cortisol in hair is a heritable trait. It shows the utility of hair cortisol as a marker for HPA activation, and a useful tool for identifying genetic influences on long term individual differences in HPA activity. The results provide support for an additive model of the effects of genes and environment on this measure of long term HPA activity.

Cross-sectional and 35-year longitudinal assessment of salivary cortisol and cognitive functioning: the Vietnam Era twin study of aging

High levels of cortisol, a sign of potential hypothalamic-pituitary-adrenal (HPA) axis dysregulation, have been associated with poor cognitive outcomes in older adults. Most cortisol research has focused on hippocampal-related abilities such as episodic memory; however, the presence of glucocorticoid receptors in the human prefrontal cortex suggests that cortisol regulation is likely to be associated with prefrontally-mediated executive function abilities. We hypothesized that elevated cortisol levels would be associated with poorer frontal-executive function in addition to episodic memory. We assessed cortisol from 15 saliva samples paralleling individual diurnal rhythms across three non-consecutive days in a group of 778 middle-aged twin men ages 51-60. Cognitive domains created from 24 standard measures included: general cognitive ability, verbal and visual-spatial ability, verbal and visual-spatial memory, short-term/immediate memory, working memory, executive function, verbal fluency, abstract reasoning, and psychomotor processing speed. Adjusting for general cognitive ability at age 20, age, race, and multiple health and lifestyle indicators, higher levels of average area-under-the-curve cortisol output across three days were significantly associated with poorer performance in three domains: executive (primarily set-shifting) measures, processing speed, and visual-spatial memory. In a 35-year longitudinal component of the study, we also found that general cognitive ability at age 20 was a significant predictor of midlife cortisol levels. These results possibly support the notion that glucocorticoid exposure is associated with cognitive functions that are mediated by frontal-striatal systems, and is not specific to hippocampal-dependent memory. The results also suggest that the direction of effect is complex.

Circadian biomarkers, circadian genes and bipolar disorders

Bipolar disorders are associated with circadian deregulations both during acute mood episodes and during euthymic periods, suggesting that these circadian rhythms may represent trait markers of the disease. Several arguments demonstrate that deregulations of circadian rhythms may be part of the pathophysiology of bipolar disorders. Abnormal quantitative and qualitative circadian disturbances have been repeatedly showed in bipolar patients, both during euthymic periods and acute phases, using different assessment tools such as actigraphy, polysomnography, and blood melatonin monitoring. In addition, many circadian physiological functions have been demonstrated to be altered in bipolar patients, such as secretion of hormones and other endogenous substances, core temperature, and fibroblasts activity. Furthermore, mood stabilizers efficiency could partially be explained by their impact on the regulation of the circadian rhythms. The implication of genetic vulnerability factors has long been demonstrated in bipolar disorders and several circadian genes have been tested for association in bipolar disorders. Although preliminary, interesting results have been obtained in several independent studies.

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.

HPA axis responsiveness to stress: implications for healthy aging

The major neuroendocrine response mediating stress adaptation is activation of the hypothalamic pituitary adrenal axis, with stimulation of corticotropin releasing hormone (CRH) and vasopressin (VP) from parvocellular neurons of the hypothalamic paraventricular nucleus, leading to stimulation of pituitary ACTH secretion and increases in glucocorticoid secretion from the adrenal cortex. Basal production and transient increases during stress of glucocorticoids and its hypothalamic regulators are essential for neuronal plasticity and normal brain function. While activation of the HPA axis is essential for survival during stress, chronic exposure to stress hormones can predispose to psychological, metabolic and immune alterations. Thus, prompt termination of the stress response is essential to prevent negative effects of inappropriate levels of CRH and glucocorticoids. This review addresses the regulation of HPA axis activity with emphasis on the mechanisms of termination of CRH transcription, which is a critical step in this process. In addition, the actions by which glucocorticoids, CRH and VP can affect the aging process will be discussed.

Salivary cortisol and prefrontal cortical thickness in middle-aged men: A twin study

Although glucocorticoid receptors are highly expressed in the prefrontal cortex, the hippocampus remains the predominant focus in the literature examining relationships between cortisol and brain. We examined phenotypic and genetic associations of cortisol levels with the thickness of prefrontal and anterior cingulate cortex regions, and with hippocampal volume in a sample of 388 middle-aged male twins who were 51-59 years old. Small but significant negative phenotypic associations were found between cortisol levels and the thickness of left dorsolateral (superior frontal gyrus, left rostral middle frontal gyrus) and ventrolateral (pars opercularis, pars triangularis, pars orbitalis) prefrontal regions, and right dorsolateral (superior frontal gyrus) and medial orbital frontal cortex. Most of the associations remained significant after adjusting for general cognitive ability, cardiovascular risk factors, and depression. Bivariate genetic analyses suggested that some of the associations were primarily accounted for by shared genetic influences; that is, some of the genes that tend to result in increased cortisol levels also tend to result in reduced prefrontal cortical thickness. Aging has been associated with reduced efficiency of hypothalamic-pituitary-adrenal function, frontal lobe shrinkage, and increases in health problems, but our present data do not allow us to determine the direction of effects. Moreover, the degree or the direction of the observed associations and the extent of their shared genetic underpinnings may well change as these individuals age. Longitudinal assessments are underway to elucidate the direction of the associations and the genetic underpinnings of longitudinal phenotypes for changes in cortisol and brain morphology.