Intraindividual variability in cortisol: Approaches, illustrations, and recommendations

Day-to-day variability of stress biomarkers during a music intervention in people living with dementia and their family caregivers

Examination of the variability of stress biomarkers among people living with dementia and their family caregivers can provide evidence of stress reactions and corresponding self-regulation capacities, but no such research has been conducted to date. The aim of this study was to examine day-to-day variability patterns of salivary biomarkers in dyads of people living with dementia and their family caregivers and to investigate differences in variability patterns between music intervention and control groups. This study involved secondary analysis of data collected during a two-group, non-randomized open trial examining the effects of an 8-week music intervention on physiological stress markers. A total of 5791 salivary samples from 34 dyads were used to analyze the variability of morning and evening cortisol and of morning dehydroepiandrosterone sulfate (DHEA-S). The variability indices employed were the intra- and inter-individual standard deviation, coefficient of variation, and intra-class correlation coefficient. We found that family caregivers in the music intervention group had significantly greater coefficients of variation for all three biomarker endpoints than those in the control group. Our findings provide evidence that stress biomarkers in family caregivers with functional self-regulation capacities may be more likely to respond to music intervention. However, stress biomarkers in people living with dementia may not be responsive to music intervention, possibly due to their dysfunctional self-regulation capacities. Future stress biomarker studies involving dyads of people living with dementia and family caregivers should consider biomarker variability patterns in determining the effectiveness of behavioral interventions.

Volatility in Expectations While Awaiting Important News

Waiting for important news is uniquely anxiety provoking, and expectations for one's outcome fluctuate throughout the wait. Emotional volatility is typically associated with negative outcomes, but little is known about volatility in expectations. In Study 1, law graduates (N = 248) estimated their chances of passing the bar exam every 2 weeks during the wait for results. Greater volatility in expectations, operationalized as the frequency with which outcome expectations changed during the wait, was associated with greater worry and more negative emotionality throughout the wait. Study 2 partially replicated these findings in a sample of Trump and Biden supporters (N = 444) awaiting the result of the 2020 presidential election. Study 2 also demonstrated a causal link between constrained (vs. volatile) expectations and worry. Our findings have implications for how best to manage one's expectations while awaiting important news, with the goal of minimizing worry and other negative emotions.

Pregnancy-specific anxiety and gestational length: The mediating role of diurnal cortisol indices

BACKGROUND

Preterm birth or shorter gestation is a common adverse pregnancy outcome. Pregnancy-specific anxiety is robustly associated with risk for shorter gestation. Hypothalamic-pituitary-adrenal (HPA) dysregulation, indicated by diurnal cortisol index variability [slope, area-under-the-curve (AUC) or cortisol awakening response (CAR)], could mediate associations between pregnancy-specific anxiety and shorter gestation. The purpose of this study was to explore whether diurnal cortisol index variability mediates associations between pregnancy-specific anxiety and gestational length.

METHODS

A sample of 149 women from the Healthy Babies Before Birth study reported pregnancy-specific anxiety in early pregnancy. Saliva samples were taken at three times during pregnancy, for two days each, at wake, 30 min post wake, noon, and evening. Diurnal cortisol indices were calculated using standard approaches. Pregnancy cortisol index variability was calculated across pregnancy timepoints. Gestational length was derived from medical charts. Covariates were sociodemographics, parity and obstetric risk. Mediation models were tested using SPSS PROCESS.

RESULTS

There was a significant indirect effect of pregnancy-specific anxiety on gestational length via CAR variability, b(SE)= -0.102(0.057), .95CI [- 0.227,- 0.008]. Higher pregnancy-specific anxiety was associated with lower CAR variability, b(SE)= -0.019(0.008), p = .022, and lower CAR variability was associated with shorter gestation, b(SE)= 5.29(2.64), p = .047. Neither AUC or slope variability mediated associations between pregnancy-specific anxiety and gestational length.

CONCLUSION

Lower CAR variability during pregnancy mediated the association between higher pregnancy-specific anxiety and shorter gestational length. Pregnancy-specific anxiety could dysregulate HPA axis activity, as indicated by lower CAR variability, demonstrating the importance of the HPA axis system in regulating pregnancy outcomes.

Impacts of cash transfer and "cash plus" programs on self- perceived stress in Africa: Evidence from Ghana, Malawi, and Tanzania

Poverty and poor mental health are closely linked. Cash transfers have significantly expanded globally. Given their objectives around poverty reduction and improving food security, a major chronic stressor in Africa, cash transfers may affect mental health outcomes. We examine impacts of three large-scale government cash transfer or cash plus programs in Ghana, Malawi, and Tanzania on self-perceived stress using an innovative, newly adapted measure for rural African settings. Linear regression models were used to estimate treatment impacts. We find that cash transfers reduced self-perceived stress in Malawi, but programs in Ghana and Tanzania had no impacts on self-perceived stress. These mixed findings, combined with recent reviews on cash transfers and mental health, suggest that cash transfers may play a role in improving mental health. However, cash alone may not be sufficient to overcome many challenges related to poverty, and complementary programming may also be needed to improve mental health.

Stressor reflections, sleep, and psychological well-being: A pre-registered experimental test of self-distanced versus self-immersed reflections

Evidence supports the effectiveness of cuing people to analyse negative autobiographical experiences from self-distanced rather than self-immersed perspectives. However, the evidence on which this expectation resides is limited largely to static snapshots of mean levels of cognitive and emotional factors. Via a pre-registered, randomised controlled trial (N = 257), we examined the differential effectiveness of self-distanced relative to self-immersed reflections on mean levels and within-person variability of sleep duration and quality as well as psychological well-being over a 5-day working week. Except for sleep quality, we found that reflecting from a psychologically distanced perspective, overall, was no more effective for mean levels and within-person variability of sleep duration, well-being, and stress-related factors than when the current self is fully immersed in the experiential reality of the event. We consider several substantive and methodological considerations (e.g., dosage, salience of stressor event) that require interrogation in future research via experimental and longitudinal observational methods.

Is conduct after capture training sufficiently stressful?

Conduct after capture (CAC) training is for personnel at risk of being captured. To be effective, it needs to be stressful. But how do we know if it is stressful enough? This study uses biomarkers and cognitive measures to evaluate CAC. Soldiers undergoing CAC were measured by the stress hormone cortisol from saliva samples at baseline and during training. The training consisted of being taken capture and put through a number of realistic and threatening scenarios, targeting survival strategies taught in the preceding week. Between scenarios, the trainees were held in a holding cell where they were monitored by a guard. The saliva samples were taken in conjunction with the scenarios. The whole training took place over a period of ~24 h. Cognitive performance was measured at baseline and after training. Three groups took part Group A (n = 20) was taken after 48 h of intense tasks leaving them in a poor resting state. Group B (n = 23) was well rested at CAC onset. Group C (n = 10) was part of a survival, evasion, resistance, and escape (SERE) instructor course. The CAC training was the same for all groups. Group A exhibited a high increase in cortisol during CAC, compared to baseline levels were multiple times as high as “expected” values. Group B exhibited elevated levels slightly lower than those of group A, they also “dropped” to “normal” levels during the latter part of the exercise. Group C displayed the least increase with only slightly elevated levels. CAC training is stressful and cortisol levels were elevated enough to satisfy the prerequisite for effective stress inoculation. No cognitive performance drop could be identified; however, several participants “froze” during the exercise due to intensive stress.

Mitochondrial phenotypes in purified human immune cell subtypes and cell mixtures

Using a high-throughput mitochondrial phenotyping platform to quantify multiple mitochondrial features among molecularly defined immune cell subtypes, we quantify the natural variation in mitochondrial DNA copy number (mtDNAcn), citrate synthase, and respiratory chain enzymatic activities in human neutrophils, monocytes, B cells, and naïve and memory T lymphocyte subtypes. In mixed peripheral blood mononuclear cells (PBMCs) from the same individuals, we show to what extent mitochondrial measures are confounded by both cell type distributions and contaminating platelets. Cell subtype-specific measures among women and men spanning four decades of life indicate potential age- and sex-related differences, including an age-related elevation in mtDNAcn, which are masked or blunted in mixed PBMCs. Finally, a proof-of-concept, repeated-measures study in a single individual validates cell type differences and also reveals week-to-week changes in mitochondrial activities. Larger studies are required to validate and mechanistically extend these findings. These mitochondrial phenotyping data build upon established immunometabolic differences among leukocyte subpopulations, and provide foundational quantitative knowledge to develop interpretable blood-based assays of mitochondrial health.

Blood mitochondrial DNA copy number: What are we counting?

There is growing scientific interest to develop scalable biological measures that capture mitochondrial (dys)function. Mitochondria have their own genome, the mitochondrial DNA (mtDNA). It has been proposed that the number of mtDNA copies per cell (mtDNA copy number; mtDNAcn) reflects mitochondrial health. The common availability of stored DNA material or existing DNA sequencing data, especially from blood and other easy-to-collect samples, has made its quantification a popular approach in clinical and epidemiological studies. However, the interpretation of mtDNAcn is not univocal, and either a reduction or elevation in mtDNAcn can indicate dysfunction. The major determinants of blood-derived mtDNAcn are the heterogeneous cell type composition of leukocytes and platelet abundance, which can change with time of day, aging, and with disease. Hematopoiesis is a likely driver of blood mtDNAcn. Here we discuss the rationale and available methods to quantify mtDNAcn, the influence of blood cell type variations, and consider important gaps in knowledge that need to be resolved to maximize the scientific value around the investigation of blood mtDNAcn.

Covariation of psychobiological stress regulation with valence and quantity of social interactions in everyday life: disentangling intra- and interindividual sources of variation

While the overall effects of social relationships on stress and health have extensively been described, it remains unclear how the experience of social interactions covaries with the activity of psychobiological stress in everyday life. We hypothesized that the valence as well as quantitative characteristics of social interactions in everyday life would attenuate psychobiological stress. Sixty healthy participants provided data for the analyses. Using an ecological momentary assessment design, participants received 6 prompts on their smartphone for 4 days. At each prompt, they reported on social interactions since the last prompt (any occurrence, frequency, duration, quality, and perceived social support), current subjective stress, and provided one saliva sample for the analyses of cortisol (sCort) and alpha-amylase (sAA). Experiencing any contact within days as well as higher daily levels of contact quality and perceived social support were associated with reduced levels of sCort. Furthermore, on a daily level, experiencing at least one contact in-between prompts more often as well as having more contacts on average attenuated the sAA output. Perceived social support and contact quality as well as higher daily contact durations were associated with lower subjective stress. For sCort, daily levels of stress moderated the effects of experiencing any contact within days while daily perceived social support moderated the effects of subjective stress. For sAA, experiencing at least one contact in-between prompts more often on a daily level moderated the effects of subjective stress. There were no between-person effects throughout all analyses. The results show ecologically valid evidence for direct attenuating effects of social interactions on psychobiological stress as well as for the stress-buffering hypothesis in everyday life. Increasing the quantity and improving the valence of social interactions on an intrapersonal level can possibly reduce psychobiological stress and prevent its consequences.

Greenspace Interventions, Stress and Cortisol: A Scoping Review

Background: Engaging with nature can profoundly impact psychological and physiological health of persons across the lifespan. Greenspace interventions (GSI) encompass a broad range of strategic, nature-based activities for overall health and wellbeing. Within the past 20 years there has been a growing interest in the access to and management of greenspace to mediate the deleterious impact of acute and chronic stress, particularly, physiologic biomarkers of stress such as cortisol. Objective: This review aims to describe the impact of greenspace interventions on cortisol, to present the current state of the science on GSIs as they impact cortisol, and to uncover any limitations of current research strategies to best inform future research. Methods: A scoping methodology was conducted to systematically study this emerging field and inform future research by mapping the literature based on the GSI category, interventional design, cortisol metrics, and subsequent analysis of cortisol. Conclusion: Considerable heterogeneity in research design, aim(s), interventional strategy, and cortisol metrics were identified from a total of 18 studies on GSIs and cortisol outcomes. While studies demonstrated a potential for the positive association between GSIs and stress relief, more rigorous research is needed to represent GSIs as an intervention to mitigate risks of stress.

Measuring psychological and physiological stress in emergency clinicians

BACKGROUND

Evidence regarding stress, team structure and decision-making has been used to inform efficacious team composition and deployment. There have been limited attempts to establish the relationship between psychological stress with physiological data within professional environments. The current study explored measures of psychological and physiological stress in Australian emergency practitioners.

METHODS

Thirty-seven staff in an Australian emergency department completed an online survey assessing freedom to make decisions, social support, and psychological job demands. Seven participants provided saliva samples three times daily for seven days (valid n=141 samples). Cortisol levels of the samples were analysed using competitive enzyme immunoassay kits, and α-amylase using kinetic enzyme assay kits.

RESULTS

Years of emergency experience was positively associated with freedom to make decisions, and social support was negatively correlated with psychological demand. No consistent pattern was observed between cortisol level and reported psychological demand, decision freedom or social support. Physical activity was not reflected in elevated α-amylase. Diurnal variation of cortisol and α-amylase was not affected by shiftwork.

CONCLUSIONS

The data supports the case for using multiple assessments to measure stress. While the psychological data is consistent with previous findings, there are possible disparities between psychological reports and physical indicators of stress.

Effectiveness of stress-relieving strategies in regulating patterns of cortisol secretion and promoting brain health

Stress leads to ill-health and disease, and with today's fast-pace western society, engaging in strategies to relieve stress is crucial for good health across the life-course. Activities such as focusing on positive characteristics, art/music therapies, mindfulness, yoga and engaging with nature and/or physical activity have been shown to reduce stress and enhance well-being. It is thought that patterns of cortisol secretion, which are regulated by the brain, are a key mediator of stress-disease and well-being-health links. Measurement of cortisol in saliva is a non-invasive and ecologically valid tool for detecting early changes in brain health, as well as evaluating the effectiveness of strategies in relieving stress and improving brain health as well as monitoring stress-related brain changes. This chapter will review the evidence that engaging in stress-relieving strategies promotes regulation and/or restoration of patterns of cortisol secretion. If such strategies are found to be effective in healthy populations, they could potentially inform ways of promoting brain health and the prevention or delay of clinical disorders involving disorders in the brain (e.g., Parkinson's disease) and symptoms experienced with such disorders. To inform this field of research, recommendations are provided for the use of salivary cortisol as a marker of early monitoring of brain health and effectiveness of stress-alleviating interventions.

Effects of cognitive-behavioral stress management training in individuals with functional somatic symptoms - an exploratory randomized controlled trial

Stress is discussed as a risk factor in the manifestation and maintenance of functional somatic (FS) symptoms. However, there is a lack of evidence regarding the effects of cognitive-behavioral stress management training (CBSM) on FS symptoms and the (potentially mediating) role of the neuroendocrine system. This study aims to examine stress-related psychological and neuroendocrine changes after receiving a brief CBSM in individuals with FS symptoms. Forty-three participants of both sexes, who reported at least one current FS symptom, were analyzed (treatment group (TG) n = 21, waitlist control group (WCG) n = 22) using mixed models. Number of symptoms, psychological stress, and salivary cortisol levels were assessed at pretreatment, posttreatment, and 6 months later. Mixed model analyses did not reveal significant differences between the TG and the WCG regarding number of FS symptoms (p > 0.05), psychological stress measures (p > 0.05) or the cortisol awakening response (CAR) (p > 0.05). The TG presented lower diurnal cortisol levels at pretreatment, posttreatment and 6 months later (p < 0.05). We did not find significant beneficial effects that were specific to CBSM. Further research should be undertaken to investigate the effects of CBSM on real life stress or laboratory stressors in subjects with FS symptoms. Moreover, learning cognitive restructuring and establishing new coping strategies into everyday life might require more time. This study is a first step in filling the gap in understanding the influences of CBSM as a brief intervention on psychological and biological aspects of stress in participants with FS symptoms and will hopefully inform larger trials of CBSM for FS symptoms.

Between the Error Bars: How Modern Theory, Design, and Methodology Enrich the Personality-Health Tradition

The study of relationships between personality traits and health has a long history in psychosomatic research. However, personality science has evolved from an understanding of personality as fixed traits to one that acknowledges that personality is dynamic. Dynamic approaches to conceptualizing and measuring personality and individual differences can enrich personality-health research. In this Presidential Address (American Psychosomatic Society, 2018), I consider how different formulations of personality-stable traits, stable signals in a noisy or variable measure, within-person changes, and intraindividual variability-can be implemented to better understand how personality is related to health and particularly to immune function. These approaches recognize and, in some cases, capitalize on the fact that personality factors can display variability as well as stability over time. They also require repeated measurement and therefore greater methodological sophistication that considers reliability and generalizability, Simpson's paradox, and the difference between variability and flexibility. Dynamic qualities of personality and individual differences potentially influence health, and designs and methodology that incorporate them can illuminate the important processes that occur inside the error bars.

Stress and Immunological Aging

Immunological aging, which encompasses age-associated declines in the immune system (immunosenescence) and increases in inflammation (inflammaging), is associated with morbidity and mortality. A growing body of research suggests stress is one factor that may accelerate immunological aging. This article provides a brief overview of immunological aging, describes key biological pathways acting at multiple lifespan stages linking stress and immunological aging, and reviews recent innovative work characterizing associations between stress in several domains and immunological aging, as well as potential protective and risk factors. Important directions for future research include careful characterizations of the complexities of stress and rigorous measurement of immunological aging processes. Advancing knowledge of stress resilience and healthy immune aging may ultimately slow disease onset and extend healthspan.

Intra-Individual Variability in Vagal Control Is Associated With Response Inhibition Under Stress

Dynamic intra-individual variability (IIV) in cardiac vagal control across multiple situations is believed to contribute to adaptive cognition under stress; however, a dearth of research has empirically tested this notion. To this end, we examined 25 U.S. Army Soldiers (all male, mean age = 30.73, standard deviation (SD) = 7.71) whose high-frequency heart rate variability (HF-HRV) was measured during a resting baseline and during three conditions of a shooting task (training, low stress, high stress). Response inhibition was measured as the correct rejection (CR) of friendly targets during the low and high stress conditions. We tested the association between the SD of HF-HRV across all four task conditions (IIV in vagal control) and changes in response inhibition between low and high stress. Greater differences in vagal control between conditions (larger IIV) were associated with higher tonic vagal control during rest, and stronger stress-related decreases in response inhibition. These results suggest that flexibility in vagal control is supported by tonic vagal control, but this flexibility also uniquely relates to adaptive cognition under stress. Findings are consistent with neurobehavioral and dynamical systems theories of vagal function.

Childhood adversity moderates the influence of proximal episodic stress on the cortisol awakening response and depressive symptoms in adolescents

Childhood adversity (CA) is known to predict sensitization to proximal stressors. Researchers have suggested that disruptions in hypothalamus-pituitary-adrenal axis functioning may be a biological mechanism. If so, CA may predict altered associations between proximal life stress and markers of cortisol secretion. We examined whether CA moderates associations between recent episodic stress and (a) the cortisol awakening response (CAR), and (b) depressive symptoms, in 241 adolescents aged 14-17 years (cortisol n = 196). Salivary cortisol was sampled at 0, 30, and 60 min postawakening for 2 days. The CAR was calculated as the area under the curve with respect to increase and waking cortisol. CA and episodic stress were assessed using contextual-threat-method-coded objective interviews. CA significantly interacted with episodic stress to predict both the CAR and depression. Among those with low CA, episodic stress predicted increased CAR but did not predict depression. For adolescents with high CA, episodic stress predicted lower CAR and higher depression. These interactions were found only for independent (uncontrollable, fateful) events, and not for dependent (self-generated) stress. Increased allostatic load resulting from CA exposure may interfere with adolescents' ability to optimally regulate their CAR in relation to recent stress, contributing to increased depression risk.