Investigating individual stress reactivity: High hair cortisol predicts lower acute stress responses

Analysis of the Effect of Exams on Perceived Stress and Temporomandibular Joint Status in Physiotherapy Students: A Pilot Study

Background and Objectives: Temporomandibular disorders or dysfunction (TMDs) encompass a range of complex conditions that impact the temporomandibular joint (TMJ), chewing muscles, teeth, and/or their supporting tissues. Stress is one of the most associated factors studied as a TMD predictor. The aim is to figure out the influence of stress on TMJ status and salivary cortisol in university students during and before exams. Materials and Methods: The study was non-experimental, employing a longitudinal, analytical, observational cohort design. The study population consisted of students enrolled in the physiotherapy degree program at the Alfonso X El Sabio University (Madrid, Spain). Data were collected during two distinct academic periods: the first period was characterized by low academic stress and no exams, and the second period coincided with the high academic stress of final course exams. The collected results included sociodemographic data, assessment of TMJ status (Fonseca Index), evaluation of muscle evaluation (masseter, upper trapezius, and sternocleidomastoid) using a MOXY Monitor (muscle oxygenation) and Neurotrac® (surface EMG, sEMG), assessment of perceived stress (PSS-14), and measurement of salivary cortisol (enzyme immunoassay with Elisa). The statistical analysis was conducted with a confidence level of 95% (p ≤ 0.05) and asymptotic or bilateral significance. Results: 70 students were analyzed during two different measurement periods. According to the Fonseca Index, initially, 37.14% of the analyzed students showed mild TMDs, 17.14% moderate TMDs, and 45.72% showed no TMDs. In general terms, stress increased with age and is related to female sex, maximum mouth opening decreased with age, oxygen saturation decreased with age and academic stress, and myoglobin concentration was related to age. Furthermore, muscle contraction decreased during higher academic stress and increased with age. For women, age was a risk factor for suffering from TMDs, and stress worsened the transition from having TMDs to having no TMDs in both sexes. Conclusions: Academic stress influences TMJ status and muscle outcomes such as oxygen saturation, myoglobin concentration, and muscle contraction, although more research is needed.

Associations of diurnal cortisol parameters with cortisol stress reactivity and recovery: A systematic review and meta-analysis

Researchers commonly assess the functioning of the hypothalamic-pituitary-adrenal (HPA) axis by measuring natural fluctuations of its end product cortisol throughout the day or in response to a standardized stressor. Although it is conceivable that an individual releasing relatively more cortisol when confronted with a laboratory stressor does the same in everyday life, inconsistencies remain in the literature regarding associations between diurnal cortisol parameters and cortisol stress responses. Hence, the current meta-analysis aggregated findings of 12 studies to examine overall associations of diurnal cortisol parameters (including total output, diurnal slope, and cortisol awakening response [CAR]) with cortisol stress reactivity and recovery in the Trier Social Stress Test (TSST). There were no significant overall associations of total output, slope, or CAR with stress reactivity. Lower total diurnal cortisol output was significantly related to better stress recovery, whereas diurnal slope and CAR were unrelated to stress recovery. Moderation analyses revealed that associations between diurnal cortisol and cortisol stress responses were dependent on the computation method of cortisol parameters, questioning the convergence and validity of commonly employed measures of stress reactivity and recovery. Overall, it seems that we cannot predict characteristics of the diurnal cortisol rhythm from a one-time measure of stress reactivity in a standardized psychosocial laboratory paradigm.

Hair cortisol concentration and its association with acute stress responses and recovery in a sample of medical students in Germany

INTRODUCTION

Experiencing acute and chronic stress can contribute to adverse health outcomes. Responses to acute stress differ between individuals (i.e., stress reactivity) and the experience of chronic stress has been discussed to be associated with acute stress responses and stress recovery. This study thus aims to investigate whether hair cortisol concentration (HCC), being an indicator for hypothalamus-pituitary-adrenal (HPA) axis activity over a prolonged period of time, is associated with acute stress responses and recovery in a sample of medical students.

MATERIAL AND METHODS

From July 2020 to July 2021, medical students (n = 54) underwent a virtual-reality Trier Social Stress Test in which their blood pressure and heart rate variability (HRV) were measured, and hair samples were taken to determine HCC. Piecewise linear growth analyses were used to investigate whether HCC (categorized into low, medium and high levels) is associated with acute stress responses and recovery regarding blood pressure and HRV.

RESULTS

Significant interaction effects in piecewise linear growth analyses showed that participants with higher levels of HCC had lower systolic and diastolic blood pressure responses compared to participants with medium levels of HCC. No significant interaction effects were observed for HRV responses or for recovery measures.

CONCLUSIONS

The study suggests that higher levels of HCC are associated with a lower cardiovascular response in terms of blood pressure to an acute stressor in medical students. Therefore, long-term HPA-axis activity may contribute to different magnitudes of acute stress responses in the autonomic nervous system. As the shown lower blood pressure responses to acute stress in individuals with increased long-term HPA-axis activity may represent inadequate stress responses, these should be further studied in order to find out more about their interaction and potential subsequent disease risks.

Acute stress influences the emotional foundations of executive control: Distinct effects on control-related affective and cognitive processes

Acute stress is known to influence performance on various task outcomes indicative of executive functioning (i.e., the top-down, goal-directed control of cognition and behavior). The most common interpretation of these effects is that stress influences control processes themselves. Another possibility, though, is that stress does not impair control per se, but instead alters the affective dynamics underlying the recruitment of control (e.g., reducing the extent to which making an error is aversive), resulting in less recruitment of control and thus poor performance. To date, however, no work has examined whether stress effects on executive function outcomes are driven by affective dynamics related to the recruitment of control. In the current study, we found that acute stress influenced-and cortisol responses related to-both executive control-related performance outcomes (e.g., post-error slowing) and control-related affective dynamics (e.g., negative affect following recruitment of control) in a modified Stroop task, but that these effects appeared to be independent of each other: The effects of stress on, and associations of cortisol with, control-related cognitive outcomes were not statistically mediated by task- or control-related affective dynamics. These results thus suggest that although stress influences affective dynamics underlying executive function, the effects of stress on executive function outcomes appear to be at least partially dependent on nonaffective processes, such as control processes themselves.

Neural habituation during acute stress signals a blunted endocrine response and poor resilience

BACKGROUND

A blunted hypothalamic-pituitary-adrenal (HPA) axis response to acute stress is associated with psychiatric symptoms. Although the prefrontal cortex and limbic areas are important regulators of the HPA axis, whether the neural habituation of these regions during stress signals both blunted HPA axis responses and psychiatric symptoms remains unclear. In this study, neural habituation during acute stress and its associations with the stress cortisol response, resilience, and depression were evaluated.

METHODS

Seventy-seven participants (17-22 years old, 37 women) were recruited for a ScanSTRESS brain imaging study, and the activation changes between the first and last stress blocks were used as the neural habituation index. Meanwhile, participants' salivary cortisol during test was collected. Individual-level resilience and depression were measured using questionnaires. Correlation and moderation analyses were conducted to investigate the association between neural habituation and endocrine data and mental symptoms. Validated analyses were conducted using a Montreal Image Stress Test dataset in another independent sample (48 participants; 17-22 years old, 24 women).

RESULTS

Neural habituation of the prefrontal cortex and limbic area was negatively correlated with cortisol responses in both datasets. In the ScanSTRESS paradigm, neural habituation was both positively correlated with depression and negatively correlated with resilience. Moreover, resilience moderated the relationship between neural habituation in the ventromedial prefrontal cortex and cortisol response.

CONCLUSIONS

This study suggested that neural habituation of the prefrontal cortex and limbic area could reflect motivation dysregulation during repeated failures and negative feedback, which might further lead to maladaptive mental states.

Stress-induced brain responses are associated with BMI in women

Overweight and obesity are associated with altered stress reactivity and increased inflammation. However, it is not known whether stress-induced changes in brain function scale with BMI and if such associations are driven by peripheral cytokines. Here, we investigate multimodal stress responses in a large transdiagnostic sample using predictive modeling based on spatio-temporal profiles of stress-induced changes in activation and functional connectivity. BMI is associated with increased brain responses as well as greater negative affect after stress and individual response profiles are associated with BMI in females (pperm < 0.001), but not males. Although stress-induced changes reflecting BMI are associated with baseline cortisol, there is no robust association with peripheral cytokines. To conclude, alterations in body weight and energy metabolism might scale acute brain responses to stress more strongly in females compared to males, echoing observational studies. Our findings highlight sex-dependent associations of stress with differences in endocrine markers, largely independent of peripheral inflammation.

The Insidious Influence of Stress: An Integrated Model of Stress, Executive Control, and Psychopathology

Although exposure to acute stress undoubtedly contributes to psychopathology, most individuals do not develop psychopathology following stress exposure. To explain this, biological, emotional, and cognitive responses to stress have been implicated, but individual differences in executive control (i.e., top-down control of cognition and behavior) measured in response to stress has only recently emerged as a potential factor contributing to psychopathology. In this review, we introduce a model-the integrated model of stress, executive control, and psychopathology-positing how the impairing effects of acute stress on executive control can contribute to psychopathology. We link to research on biological, emotional, and cognitive processes, all of which can be impacted by executive control, to propose a framework for how poorer executive control under conditions of acute stress can contribute to psychopathology. This integrated model is intended to further our understanding of who is more susceptible to the negative consequences of stress.

Exploration of possible sex bias in acute social stress research: a semi-systematic review

Stress can have a significant impact on the daily lives of individuals and can increase vulnerability to a number of medical conditions. This study aims to estimate the ratio of male to female participants in acute social stress research in healthy individuals. We examined original research articles published over the last 20 years. Each article was screened to determine the total number of female and male participants. We extracted data from 124 articles involving a total of 9539 participants. A total of 4221 (44.2%) participants were female, 5056 (53.0%) were male and 262 (2.7%) were unreported. Articles incorporating only females were significantly underrepresented compared to articles incorporating only males. Forty articles (63.5%) which presented data from both females and males, failed to analyse and interpret the results by sex, a significant methodological limitation. In conclusion, in the literature published over the last 20 years, female participants are significantly underrepresented. In the studies where females are represented, severe methodological limitations are apparent. Researchers should be conscious of sexual dimorphism, menstrual phase and use of hormonal contraception, which may impact the interpretation of their results.

Hypocortisolemic reactivity to acute social stress among lonely young women

We examined biopsychosocial stress of acute social pain in relation to chronic loneliness. Hypotheses: 1) Cyberball exclusion (vs. inclusion) would be associated with lower cortisol reactivity to a speech task, and 2) loneliness would moderate the relationship between social exclusion and cortisol reactivity to a speech task, such that higher loneliness would be linked to lower cortisol. Participants (n = 31, women, aged 18-25, 51.6% non-Hispanic white) were randomized to be excluded or included in a game of Cyberball, then completed a speech task. Salivary cortisol was measured at baseline, pre-speech, post-speech, and 15 minutes post-speech. Cortisol reactivity was calculated using area under the curve-increase (AUCi). ANOVA revealed a non-significant, meaningful effect of Cyberball exclusion on cortisol AUCi (p=.103, ηp2=.10), accounting for contraceptive use. Moderation analysis revealed among women with high loneliness, women in the exclusion condition had significantly lower cortisol reactivity than women in the inclusion condition (p=.001). For women with low and medium loneliness, there were no significant differences by Cyberball condition. In sum, lonely young women who are excluded may have hypocortisolemic responses to social stress. Results are consistent with literature suggesting that chronic stress is linked to lower cortisol responses, which is linked to negative physical health outcomes.

Dysfunction of the hypothalamic-pituitary adrenal axis and its influence on aging: the role of the hypothalamus

As part of the hypothalamic-pituitary adrenal (HPA) axis, the hypothalamus exerts pivotal influence on metabolic and endocrine homeostasis. With age, these processes are subject to considerable change, resulting in increased prevalence of physical disability and cardiac disorders. Yet, research on the aging human hypothalamus is lacking. To assess detailed hypothalamic microstructure in middle adulthood, 39 healthy participants (35-65 years) underwent comprehensive structural magnetic resonance imaging. In addition, we studied HPA axis dysfunction proxied by hair cortisol and waist circumference as potential risk factors for hypothalamic alterations. We provide first evidence of regionally different hypothalamic microstructure, with age effects in its anterior-superior subunit, a critical area for HPA axis regulation. Further, we report that waist circumference was related to increased free water and decreased iron content in this region. In age, hair cortisol was additionally associated with free water content, such that older participants with higher cortisol levels were more vulnerable to free water content increase than younger participants. Overall, our results suggest no general age-related decline in hypothalamic microstructure. Instead, older individuals could be more susceptible to risk factors of hypothalamic decline especially in the anterior-superior subregion, including HPA axis dysfunction, indicating the importance of endocrine and stress management in age.

Hair Cortisone Predicts Lower Stress-induced Salivary Cortisol Response: Resting-state Functional Connectivity Between Salience and Limbic Networks

Previous studies revealed that high long-term hypothalamic-pituitaryadrenal (HPA) axis activity measured by the hair cortisol concentrations predicts lower acute stress cortisol response and reported the influences of hair cortisol on brain activity during acute stress exposure. However, considering that long-term HPA axis activity has a close relationship with the brain's resting-state functional connectivity (RSFC), the current study aimed to explore the role of RSFC between limbic and salience network in this relationship. Seventy-seven healthy participants underwent resting-state imaging scans before performing the acute ScanSTRESS task. Saliva samples were collected to assess the levels of acute stress salivary cortisol. Hair samples were also collected, and the corticosteroid concentration extracted from these samples were used as a biomarker of long-term HPA axis activity. High hair cortisone (HairE) levels predicted lower acute stress cortisol response. Moreover, high HairE levels were significantly correlated with enhanced RSFC between limbic and salience networks, while RSFC was negatively associated with acute stress cortisol response. Importantly, the RSFC between left insula and left parahippocampus mediated the association between HairE and acute cortisol stress response. Taken together, this study uncovers the important role of RSFC between salience and limbic networks in the long-term relationship between HairE and acute cortisol response and contributes to a deeper understanding of the individual differences in acute stress response.

Separating the influences of means and daily variations of sleep on the stress-induced salivary cortisol response

BACKGROUND

Previous research regarding the effects of sleep quality and quantity on the acute stress response has yielded inconsistent findings. This may be attributed to various factors, including composite sleep components (i.e., means and daily variations) and mixed cortisol stress response (i.e., reactivity and recovery). Thus, this study aimed to separate the effects of means and daily variations of sleep on the reactivity and recovery of cortisol responses to psychological challenges.

METHODS

In study 1, we recruited 41 healthy participants (24 women; age range, 18-23 years), monitored their sleep during seven consecutive days via wrist actigraphy and sleep diaries, and adopted the Trier Social Stress Test (TSST) paradigm to induce acute stress. Study 2 consisted of a validation experiment using the ScanSTRESS paradigm, which included 77 additional healthy individuals (35 women; age range, 18-26 years). Similarly to the TSST, the ScanSTRESS induces acute stress using uncontrollability and social evaluation. In both studies, saliva samples from the participants were collected before, during, and after the acute stress task.

RESULTS

Using residual dynamic structural equation modeling, both study 1 and study 2 demonstrated that higher means of objective sleep efficiency, and longer means of objective sleep duration were related to greater cortisol recovery. In addition, fewer daily variations in objective sleep duration were associated with greater cortisol recovery. However, there was no correlation between sleep variables and cortisol reactivity, except for the daily variations in objective sleep duration in study 2. No correlation was observed between subjective sleep and cortisol response to stress.

CONCLUSIONS

The present study separated two features of multi-day sleep patterns and two components of cortisol stress response, providing a more comprehensive picture of the effect of sleep on the stress-induced salivary cortisol response, and contributing to the future development of targeted interventions for stress-related disorders.

Revisiting the stress recovery hypothesis: Differential associations of cortisol stress reactivity and recovery after acute psychosocial stress with markers of long-term stress and health

Exposure to excessive and long-term stress may result in dysregulation of the stress system, including the acute stress response. In particular, failure to downregulate stress-related reactivity may lead to prolonged stress responses and the accumulation of allostatic load. However, the contribution of altered acute cortisol recovery to chronic stress and associated health impairments has often been neglected. Addressing this lack of research, we explored whether recovery from - more so than reactivity to - acute stress captures the basal stress load of an individual. Using Piecewise Growth Curve Models with Landmark Registration, we analyzed cortisol reactivity and recovery slopes of 130 healthy participants exposed to a standardized psychosocial laboratory stressor. Reactivity and recovery were predicted by measures indicative of long-term stress and its downstream effects, including self-report questionnaires, diurnal cortisol indices [cortisol awakening response (CAR); diurnal cortisol slope], markers of pro-inflammatory activity (interleukin-6; high-sensitive C-reactive protein), and hippocampal volume (HCV). Among these measures, only an increased CAR was specifically and consistently associated with relatively impaired recovery. Since the CAR represents the physiological enhancement needed to meet the anticipated demands of the forthcoming day, this finding may highlight the contribution of cognitive processes in determining both CAR and acute stress recovery. Furthermore, greater cortisol reactivity covaried with smaller HCV, showing that increased acute reactivity translates to health-relevant downstream effects. The lack of further associations between long-term and acute stress measures may arise from biases in self-reported chronic stress and the rigorously health-screened study sample. Overall, our findings suggest that while cortisol stress recovery might not supersede reactivity as an indicator of the long-term stress load or associated health effects, recovery and reactivity have differential utility in describing individuals' allostatic states.

Sex-dependent multimodal response profiles to psychosocial stress

INTRODUCTION

Sex differences in stress reactions are often reported in the literature. However, the sex-dependent interplay of different facets of stress is still not fully understood. Particularly in neuroimaging research, studies on large samples combining different indicators of stress remain scarce.

MATERIALS AND METHODS

In a functional magnetic resonance imaging study, a sample of 140 healthy participants (67 females using oral contraceptives) underwent a standardized stress induction protocol, the ScanSTRESS. During the experiment, salivary cortisol and subjective ratings were obtained at multiple time points and heart rate was recorded.

RESULTS

Sex differences emerged in different facets of the stress response:Women reacted with enhanced subjective feelings of stress and increases in heart rate, while men showed more pronounced neural activation in stress-related brain regions such as the inferior frontal gyrus and insula. Subjective feelings of stress and (para) hippocampal activity were negatively related in women,whereas a slightly positive association was observed in men.

DISCUSSION

These results provide further insight in the sex-specific stress response patterns. Moreover, they emphasize the role of the hippocampus in the regulation of the stress response. This paves the way for the identification of sex-dependent vulnerability factors that can, in the future, be implemented in the prevention and treatment of stress-related disorders.

Socioeconomic status in early adolescence predicts blunted stress responses in adulthood

Individuals who grow up in families with lower socioeconomic status (SES) tend to experience disproportionate rates of chronic stress. The “freeze” response, characterized by blunted cardiovascular reactivity and reduced engagement with the environment, is associated with chronic stress and may be utilized when an individual is unable to escape or overcome environmental stressors. Using a diverse community sample of 184 adolescents followed from the age of 13 to 29 years, along with their friends and romantic partners, this study examined links between family SES and stress responses in adulthood. Low family SES at the age of 13 years directly predicted blunted heart rate responding and fewer attempts to answer math problems during a modified version of the Trier Social Stress Task at the age of 29 years. Indirect effects were found from low family SES to blunted respiratory sinus arrhythmia responding and the number of words spoken during a speech task. SES at the age of 29 years mediated many of these relations. Findings held after accounting for a number of potential confounds, including adolescent academic and attachment functioning and body mass index. We interpret these findings as evidence that low familial SES may predict freezing‐type responses in adulthood.

Comparing two psychosocial stress paradigms for imaging environments - ScanSTRESS and fNIRS-TSST: correlation structures between stress responses

The present post-hoc analysis of two independent studies conducted in different laboratories aimed at comparing reactions of stress activation systems in response to two different psychosocial stress induction paradigms. Both paradigms are based on the Trier Social Stress Test and suited for neuroimaging environments. In an in-depth analysis, data from 67 participants (36 men, 31 women) from a functional magnetic resonance imaging study implementing ScanSTRESS were compared with data from a functional near-infrared spectroscopy (fNIRS) study implementing the so-called 'fNIRS-TSST' including 45 participants (8 men, 37 women). We tested the equivalence of correlation patterns between the stress response measures cortisol, heart rate, affect, and neural responses in the two samples. Moreover, direct comparisons of affective and neural responses were made. Similar correlation structures were identified for all stress activation systems, except for neural contrasts of paradigm conditions (stress vs. control) showing significant differences in association with cortisol, heart rate, and affective variables between the two samples. Furthermore, both stress paradigms elicited comparable affective and cortical stress responses. Apart from methodological differences (e.g., procedure, timing of the paradigms) the present analysis suggests that both paradigms are capable of inducing moderate acute psychosocial stress to a comparable extent with regard to affective and cortical stress responses. Moreover, similar association structures between different stress response systems were found in both studies. Thus, depending on the study objective and the respective advantages of each imaging approach, both paradigms have demonstrated their usefulness for future studies.

Psychobiological effects of chronic ethnic discrimination in Turkish immigrants: Stress responses to standardized face-to-face discrimination in the laboratory

OBJECTIVE

Ethnic discrimination negatively affects the health of ethnic minorities. The dysregulation of psychobiological stress systems, such as the autonomic nervous system (ANS) or the hypothalamic-pituitary-adrenal (HPA) axis, might be an intermediary in this association and chronicity of ethnic discrimination may matter. We studied stress responses to a standardized discriminatory event in Turkish immigrants living in Austria.

BACKGROUND

Seventy-two male Turkish immigrants were recruited; n = 35 had experienced high levels of ethnic discrimination (high), n = 37 infrequent ethnic discrimination (low). During a two-hour laboratory appointment, they underwent a previously validated 10-minute ethnic discrimination paradigm, i.e., a simulated physician's consultation with verbal and non-verbal discriminatory cues. Perceived stress, perceived discrimination, salivary cortisol, and alpha-amylase were assessed seven times, and ANS measures (heart rate, heart rate variability, and electrodermal activity) were measured continuously. In addition, hair cortisol concentrations were determined.

RESULTS

The ethnic discrimination paradigm elicited stress responses across all outcomes in both groups. Compared to the low group, the high group reported higher levels of perceived stress and discrimination, exhibited a less steep increase in cortisol in response to the paradigm, and showed higher hair cortisol concentrations. No group differences were found regarding ANS measures.

CONCLUSIONS

The combination of high subjective stress, flattened cortisol responses, and relatively high hair cortisol concentrations may indicate a dysregulation of the HPA axis in chronic ethnic discrimination. A better understanding of the psychobiological effects of chronic ethnic discrimination is crucial given that alterations in stress response systems may, over time, lead to illness and ultimately to substantial health inequities in ethnic minorities.

The Hippocampal-Ventral Medial Prefrontal Cortex Neurocircuitry Involvement in the Association of Daily Life Stress With Acute Perceived Stress and Cortisol Responses

OBJECTIVE

Daily life stressors include everyday irritants, hassles, and inconveniences, such as problems in traffic and unexpected work deadlines. A growing body of research has suggested higher daily stress is associated with blunted cortisol response to acute psychosocial stressors. However, so far, the neural mechanism underlying this association has not been elucidated. The current study aimed to examine the role of stress neurocircuitry between the hippocampus and the ventral medial prefrontal cortex in this relationship.

METHODS

To this end, as an index of daily stress in 44 young healthy individuals (23 females; mean [standard deviation] age = 19.07 [1.11] years), the total stressful rating score of daily life stress events that occurred in a 24-hour period was quantified. Individuals were then administered a modified version of the Montreal Imaging Stress Task while undergoing functional magnetic resonance imaging scans, and their saliva samples were collected for assessment of the stress hormone cortisol.

RESULTS

Results revealed that a higher level of daily stress was associated with lower salivary cortisol secretion (r = -0.39, p = .008) and lower activation of the left hippocampus (tpeak = -5.51) in response to the Montreal Imaging Stress Task. Furthermore, a higher level of daily stress was associated with stronger functional connectivity between the left hippocampus and the ventral medial prefrontal cortex/subgenual anterior cingulate cortex (tpeak = 4.91, R2= 0.365).

CONCLUSIONS

Taken together, the current study suggested a possible neurocircuitry of the hippocampus and ventral medial prefrontal cortex in the relationship between daily life stress and acute psychosocial stress.

Stress research during the COVID-19 pandemic and beyond

The COVID-19 pandemic confronts stress researchers in psychology and neuroscience with unique challenges. Widely used experimental paradigms such as the Trier Social Stress Test feature physical social encounters to induce stress by means of social-evaluative threat. As lockdowns and contact restrictions currently prevent in-person meetings, established stress induction paradigms are often difficult to use. Despite these challenges, stress research is of pivotal importance as the pandemic will likely increase the prevalence of stress-related mental disorders. Therefore, we review recent research trends like virtual reality, pre-recordings and online adaptations regarding their usefulness for established stress induction paradigms. Such approaches are not only crucial for stress research during COVID-19 but will likely stimulate the field far beyond the pandemic. They may facilitate research in new contexts and in homebound or movement-restricted participant groups. Moreover, they allow for new experimental variations that may advance procedures as well as the conceptualization of stress itself. While posing challenges for stress researchers undeniably, the COVID-19 pandemic may evolve into a driving force for progress eventually.

Association of Innate and Acquired Aerobic Capacity With Resilience in Healthy Adults: Protocol for a Randomized Controlled Trial of an 8-Week Web-Based Physical Exercise Intervention

BACKGROUND

Physical activity alleviates chronic stress. The latest research suggests a relationship between resilience and physical fitness. Beneficial adaptations of the hypothalamic-pituitary-adrenal axis, sympathetic nervous system, endocannabinoid system, and tryptophan pathway, which are induced by an active lifestyle, are considered to be conducive to resilience. However, detailed knowledge on the molecular link between the effects of acute and chronic physical exercise and improved resilience to stress in humans is missing. Moreover, the relationship between innate and acquired aerobic capacity and resilience is poorly understood.

OBJECTIVE

The aim of this study is to implement a human exercise intervention trial addressing the following main hypotheses: a high innate aerobic capacity is associated with high resilience to stress, and web-based physical exercise training improves aerobic capacity of physically inactive adults, which is accompanied by improved resilience. In this setting, we will analyze the relationship between resilience parameters and innate and acquired aerobic capacity as well as circulating signaling molecules.

METHODS

A total of 70 healthy, physically inactive (<150 minutes/week of physical activity) adults (aged 18-45 years) will be randomly assigned to an intervention or control group. Participants in the intervention group will receive weekly training using progressive endurance and interval running adapted individually to their remotely supervised home training performance via web-based coach support. A standardized incremental treadmill exercise test will be performed before and after the intervention period of 8 weeks to determine the innate and acquired aerobic capacity (peak oxygen uptake). Before and after the intervention, psychological tests and questionnaires that characterize parameters implicated in resilience will be applied. Blood and saliva will be sampled for the analysis of cortisol, lactate, endocannabinoids, catecholamines, kynurenic acid, and further circulating signal transducers. Statistical analysis will provide comprehensive knowledge on the relationship between aerobic capacity and resilience, as well as the capacity of peripheral factors to mediate the promoting effects of exercise on resilience.

RESULTS

The study was registered in October 2019, and enrollment began in September 2019. Of the 161 participants who were initially screened via a telephone survey, 43 (26.7%) fulfilled the inclusion criteria and were included in the study. Among the 55% (17/31) of participants in the intervention group and 45% (14/31) of participants in the control group who completed the study, no serious adverse incidents were reported. Of 43 participants, 4 (9%) withdrew during the program (for individual reasons) and 8 (19%) have not yet participated in the program; moreover, further study recruitment was paused for an indeterminate amount of time because of the COVID-19 pandemic.

CONCLUSIONS

Our study aims to further define the physiological characteristics of human resilience, and it may offer novel approaches for the prevention and therapy of mental disorders via an exercise prescription.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/29712.

Don't stress, it's under control: Neural correlates of stressor controllability in humans

Animal research has repeatedly shown that control is a key variable in the brain's stress response. Uncontrollable stress triggers a release of monoamines, impairing prefrontal functions while enhancing subcortical circuits. Conversely, control over an adverse event involves prefrontally mediated downregulation of monoamine nuclei and is considered protective. However, it remains unclear to what extent these findings translate to humans. During functional magnetic resonance imaging, we subjected participants to controllable and uncontrollable aversive but non-painful electric stimuli, as well as to a control condition without aversive stimulation. In each trial, a symbol signalled whether participants could terminate the stressor through correct performance in a button-matching task or whether the stressor would be randomly terminated, i.e., uncontrollable. Along with neural responses, we assessed participants' accuracy, reaction times, and heart rate. To relate neural activations and subjective experience, we asked participants to rate perceived control, helplessness, and stress. Results were largely in line with our hypotheses. The vmPFC was generally deactivated by aversive stimulation, but this effect was attenuated when participants could terminate the stressor compared to when their responses had no effect. Furthermore, activation in stress-responsive regions, including the bilateral insula, was reduced during controllable trials. Under uncontrollable aversive stimulation, greater vmPFC recruitment was linked to reduced feelings of helplessness. An investigation of condition-dependant differences in vmPFC connectivity yielded no significant results. Our findings further corroborate animal research and emphasise the role of the vmPFC in controllability-dependant regulation of stress responses. Based on the results, we discuss future directions in the context of resilience research and mental health promotion.

Sex-Specific Interaction Between Cortisol and Striato-Limbic Responses to Psychosocial Stress

Although women and men differ in psychological and endocrine stress responses as well as in the prevalence rates of stress-related disorders, knowledge on sex differences regarding stress regulation in the brain is scarce. Therefore, we performed an in-depth analysis of data from 67 healthy participants (31 women, taking oral contraceptives), who were exposed to the ScanSTRESS paradigm in a functional magnetic resonance imaging study. Changes in cortisol, affect, heart rate and neural activation in response to psychosocial stress were examined in women and men as well as potential sex-specific interactions between stress response domains. Stress exposure led to significant cortisol increases, with men exhibiting higher levels than women. Depending on sex, cortisol elevations were differently associated with stress-related responses in striato-limbic structures: higher increases were associated with activations in men but with deactivations in women. Regarding affect or heart rate responses, no sex differences emerged. Although women and men differ in their overall stress reactivity, our findings do not support the idea of distinct neural networks as the base of this difference. Instead, we found differential stress reactions for women and men in identical structures. We propose considering quantitative predictors such as sex-specific cortisol increases when exploring neural response differences of women and men.

Cognitive emotion regulation withstands the stress test: An fMRI study on the effect of acute stress on distraction and reappraisal

Cognitive emotion regulation is a key mechanism for the maintenance of mental health, but may fail, when individuals are exposed to acute stress. To date, it is not well understood whether and to what extent acute stress effects contribute to impairments in emotion regulation capacities as the sparse existing studies have yielded heterogeneous results, indicating that stress timing might be a crucial factor. In the present study, 81 healthy participants underwent either an acute stress task (ScanSTRESS-C; n = 40) or a control condition (n = 41) while lying in the MRI scanner. In the subsequent Cognitive Emotion Regulation Task (CERT), participants were confronted with neutral or negative pictures and instructed to either view them, or regulate their upcoming emotions using either distraction or reappraisal. Subjective ratings of affective state as well as functional brain imaging data served to indicate emotion regulation. The results showed a successful stress manipulation as indicated by group differences in subjective wellbeing, saliva cortisol concentrations, heart rate, and functional brain activity in regions implicated in stress processing. With respect to emotion regulation, CERT data revealed a significant regulation effect at the neural and behavioral level (less negative emotional ratings after reappraisal and distraction trials compared to view trials) in both groups. However, no significant group differences were observed, neither in BOLD responses to the CERT, nor in behavioral ratings. Contrary to previous studies, our study did not reveal further evidence of stress-related effects on emotion regulation, potentially being related to differences between studies in experimental setting, timing, and procedures. This study therefore underlines the need of future studies that disentangle the complex interplay of stress and emotion regulation and identify different factors influencing their bidirectional relationship.