Fight or flight: The effect of heart rate reactivity on acute stress-induced food intake

The 'fight-or-flight-reaction' describes the suppression of all irrelevant functions like food intake during the acute stress response. However, heart rate reactivity and food intake under acute stress has not been investigated. Therefore, the aim of this study was to investigate the effect of high and low heart rate reactivity on food intake following an acute laboratory stress paradigm in individuals with healthy weight. Fifty-six men and women with healthy weight (BMI: M = 21.82 ± 1.53 kg/m²) were categorized into high heart rate reactors (H-HRR) and low heart rate reactors (L-HRR). After the stress paradigm of the Trier Social Stress Test (TSST), total energy intake was measured in a standardized laboratory meal. H-HRR demonstrated a significantly lower appetite (z = -3.133, p≤ 0.01) and food intake (t(49.13) = 2.253, p≤ 0.05, d= 0.68) after the TSST compared to the L-HRR. No differences in the stress perception and cognitive appraisal could be found between the two reactor groups. These results suggest that the stress-induced heart rate reactivity might be a responsible factor in the stress-eating paradox. In view of the divergent results of stress-induced eating studies in laboratory setting with acute stressors, it is highly important to control the effect of the heart rate reactivity on food intake.

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 acute psychosocial stress with oxidative stress: Evidence from serum analysis

Growing evidence implicates an association between psychosocial stress and oxidative stress (OxSt) although there are not yet reliable biomarkers to study this association. We used a Trier Social Stress Test (TSST) and compared the response of a healthy control group (HC; N=10) against the response of a schizophrenia group (SCZ; N=10) that is expected to have higher levels of OxSt. Because our previous study showed inconsistent changes in conventional molecular markers for stress responses in the neuroendocrine and immune systems, we analyzed the same serum samples using a separate reducing capacity assay that provides a more global measurement of OxSt. This assay uses the moderately strong oxidizing agent iridium (Ir) to probe a sample's reducing capacity. Specifically, we characterized OxSt by this Ir-reducing capacity assay (Ir-RCA) using two measurement modalities (optical and electrochemical) and we tuned this assay by imposing an input voltage sequence that generates multiple output metrics for data-driven analysis. We defined five OxSt metrics (one optical and four electrochemical metrics) and showed: (i) internal consistency among each metric in the measurements of all 40 samples (baseline and post TSST for N=20); (ii) all five metrics were consistent with expectations of higher levels of OxSt for the SCZ group (three individual metrics showed statistically significant differences); and (iii) all five metrics showed higher levels of OxSt Post-TSST (one metric showed statistically significant difference). Using multivariant analysis, we showed that combinations of OxSt metrics could discern statistically significant increases in OxSt for both the SCZ and HC groups 90 min after the imposed acute psychosocial stress.

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Ir-reducing capacity assay (Ir-RCA) provides a robust global measure of oxidative stress in serum.

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The multiple oxidative stress (OxSt) output metrics of this Ir-RCA are useful for data-driven analysis.

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The combination of OxSt metrics can discern significant increases in OxStwithin 90 mins of an imposed psychosocial stress.

The Role of Stress in Bipolar Disorder

Stress is a major risk factor for bipolar disorder. Even though we do not completely understand how stress increases the risk for the onset and poorer course of bipolar disorder, knowledge of stress physiology is rapidly evolving. Following stress, stress hormones - including (nor)adrenaline and corticosteroid - reach the brain and change neuronal function in a time-, region-, and receptor-dependent manner. Stress has direct consequences for a range of cognitive functions which are time-dependent. Directly after stress, emotional processing is increased at the cost of higher brain functions. In the aftermath of stress, the reverse is seen, i.e., increased executive function and contextualization of information. In bipolar disorder, basal corticosteroid levels (under non-stressed conditions) are generally found to be increased with blunted responses in response to experimental stress. Moreover, patients who have bipolar disorder generally show impaired brain function, including reward processing. There is some evidence for a causal role of (dysfunction of) the stress system in the etiology of bipolar disorder and their effects on brain system functionality. However, longitudinal studies investigating the functionality of the stress systems in conjunction with detailed information on the development and course of bipolar disorder are vital to understand in detail how stress increases the risk for bipolar disorder.

Facial emotion recognition in borderline patients is unaffected by acute psychosocial stress

Borderline Personality Disorder (BPD) is characterized by difficulties in social cognition and social interactions, which exacerbate under stress. A previous study found better facial emotion recognition (FER) in patients with personality disorders and healthy controls (HC) after stress. We recently reported that emotional empathy scores, i.e. the emotional response to another person's emotional state, were significantly lower in BPD patients than in HC after psychosocial stress. Cognitive empathy scores remained unaltered. The present study aims to further investigate the effect of psychosocial stress induced by the Trier Social Stress Test (TSST) on FER as part of social cognition in patients with BPD. We randomized 43 women with BPD and 46 female HC to either the TSST or a placebo condition. Afterwards, participants were asked in an emotion recognition test to identify emotions in faces showing anger or sadness at low and high intensity. Both groups recognized emotions better at high intensity compared with low intensity. There was no effect of stress on FER performance and we found no difference between groups. This is in line with prior research on social cognition in BPD patients demonstrating that the ability to understand another person's perspective might be unaffected by acute stress.

Cortisol reactivity in social anxiety disorder: A highly standardized and controlled study

In order to understand the psychopathology of the social anxiety disorder (SAD) at the neuroendocrine level, standardized experimental studies on endocrine and physiological markers are necessary, especially since empirical data are still ambiguous. Hence, differences in both, the autonomic nervous system (ANS) and the endocrine stress responses (ACTH, salivary and plasma cortisol) were investigated in a particularly homogenous sample after a standardized stressor (Trier Social Stress Test). The sample consisted of n  = 35 patients with SAD, age, and gender matched to n  = 35 healthy controls (HC). In terms of the heart rate, the response pattern was comparable in both groups. Concerning ACTH, no significant group differences in the response pattern nor in the total output (AUC_G) were exhibited. Significant differences were noticeable only in the plasma cortisol response pattern with less total output (AUC_G) in patients suggesting a blunted response. The salivary cortisol response indicated comparable patterns between groups. However, the patients' total output (AUC_G) was significantly smaller relative to the controls. In sum, evidence for a hypo-responsiveness of the HPA-axis in SAD by means of blood cortisol was observed, with no differences in ACTH between the two groups. This reduced reactivity of the HPA-axis might be associated with an inability to elicit an adequate hormone release, possibly accompanied by an enhanced perception of the stress stimulus. This might be explained by an adaptation of the adrenocortical system due to prolonged repeated stress exposure such as social evaluation.

The effect of restrained eating on acute stress-induced food intake in people with obesity

Restrained eating, defined as a form of intense dieting or restrictive food intake of specific macronutrients or types of food with sporadic episodes of overeating, results in an increased risk of overweight and obesity. Acute stress situations cause irregular eating patterns and are connected to restrained eating. Therefore, the present study investigates the effect of high/low restrained eating on eating behavior in people with obesity after standardized acute stress induction as well as resting condition. Fifty men and women with obesity (BMI: 33.62 ± 3.93 kg/m²) were categorized into high restrained eaters (HRE) and low restrained eaters (LRE). The total energy intake was measured during a standardized laboratory meal after a resting and stress condition (Trier Social Stress Test) on two separate days. HRE and LRE showed differences in the total energy intake in response to acute stress but not after resting condition (F_{(1, 47)} = 9.188, p = .004, η2 = 0.164). Lower total energy intake after stress compared to resting condition could be observed in HRE (t (23) = -2.617, p = .015). LRE showed higher total energy intake after stress than after resting condition (t (25) = 2.155, p = .041). The present data suggest that restrained eating behavior might be an influencing factor for stress-induced eating in obesity. It is highly necessary to understand the association between restrained eating behavior, acute stress and obesity for the improvement of the behavioral intervention of dietary restriction.

HPA axis responses to psychological challenge linking stress and disease: What do we know on sources of intra- and interindividual variability?

Stress is an ubiquitous phenomenon with significant impact on human physiology when it lasts too long, when it is too intense, or when it hits vulnerable individuals. Examining the mechanisms linking stress exposure with health and disease is an important endeavor in psychoneuroendocrine research. Empirical evidence so far revealed large intra- as well as inter-individual variability in hypothalamic-pituitary-adrenal (HPA) axis responses to acute psychosocial stress, showing that the HPA axis is a highly adaptive system. Thus, the characterization of intra- und inter-individual patterns of HPA axis reactivity is of high scientific interest and forms the basis on which mechanistic links between stress response (dys)regulation and health impairments can be examined. To date, basic knowledge has been, and still is, accumulated on demographic, biological (including genetic and epigenetic) factors, lifestyle behavioral variables, consumption of substances and medication, psychological and personality factors, as well as on methodological aspects. Besides this, there is also very recent progress in respect to the development of laboratory stress paradigms that can be applied in virtual reality or inside an MRI-scanner. In sum, the present review updates our current knowledge on moderating and intervening factors as sources of intra- und inter-individual variability in human cortisol stress responses and offers recommendations for future research designs.

Virtual social support buffers stress response: An experimental comparison of real-life and virtual support prior to a social stressor

BACKGROUND AND OBJECTIVES

Face-to-face and text-based social support have been shown to attenuate stress responses in past studies. Yet as social interactions increasingly take place online by means of virtual humans, our objective was to examine whether different forms of social support (virtual vs. real) prior to the Trier Social Stress Test (TSST) would also decrease stress. Additionally, the effect on subsequent real-life social behaviors (helping and approach) was evaluated while controlling for affective states and social presence.

METHODS

56 participants were either supported by an avatar, an agent, a real human or received no support before completing the TSST and two subsequent social behavior tasks (pen task and seating task).

RESULTS

Results show no difference in agency regarding social presence. Yet, participants with agent support and no support had significantly higher heart rates during the TSST and reported to be more worried. Also, they were more irritated and showed significantly slower helping reactions (picking up pens).

LIMITATIONS

A limitation to this study is that only emotional verbal and non-verbal support were provided by a stranger. Different forms of support as well as a different source (i.e., a friend) may have a more pronounced effect on stress buffering.

CONCLUSIONS

Virtual social support is as effective as face-to-face support in terms of stress buffering, as long as the recipient has the impression that it is provided by another human (via an avatar). This has wide ranging implications not only for health-related application in prevention and treatment but also for further research.

Acute and past subjective stress influence working memory and related neural substrates

Stress has been proposed to affect cognitive control capacities, including working memory (WM) maintenance. This effect may depend on variability in stress reactivity and past subjective stress. However, as most studies employed between-subjects designs, evidence for within-subject stress effects remains scarce. To understand the role of intra-individual stress effects on WM, we adopted a within-subject design to study how acute stress, variability in stress reactivity, and past subjective stress influence behavioral and neural WM mechanisms. Thirty-four healthy males performed a WM task during functional magnetic resonance imaging (fMRI) in a control versus acute stress condition following the Trier Social Stress Test, a validated psychosocial stressor method. We tested for stress effects on WM performance and related neural activation by associating them with individual acute stress responsivity and past subjective stress experience using retrospective self-report questionnaires. We found no evidence of an effect of acute stress or related stress-reactivity on intra-individual WM performance. However, past subjective stress negatively influenced acute stress-induced changes to WM. On the neural level, acute stress reduced WM-related activation in the dorsolateral prefrontal cortex (dlPFC). The observed negative influence of inter-individual variability in past subjective stress experience on changes in WM performance, suggests that past subjective stress might induce vulnerability for impairing effects of acute stress on cognitive functioning. Because acute stress reduced WM-related dlPFC activation while WM performance remained unaffected, acute stress might boost neural processing efficiency in this group of high performing healthy individuals. Our study suggests that measures of past subjective stress should be considered when studying and interpreting the effects of acute stress on cognition.

Investigating psychological and physiological responses to the Trier Social Stress Test in young adults with insomnia

OBJECTIVE

Stress and hyperarousal both contribute to insomnia. Elevated stress-related sleep reactivity is associated with hyperarousal, and might constitute a vulnerability to future insomnia. The present study examined acute stress-induced arousal and its association with nocturnal sleep.

METHODS

Participants were 30 healthy adults (66.7% female, M_age = 26.7 years): 10 with insomnia (INS) and 20 good sleepers with high vulnerability (HV) or low vulnerability (LV) to insomnia. They underwent two consecutive nights of polysomnography. During the evening preceding the second night, the Trier Social Stress Test (TSST) was administered, and psychological and physiological arousal indices were assessed.

RESULTS

The TSST elicited an increase in psychological and physiological arousal in all three groups. The INS group showed greater acute cortisol response (p < 0.05) and secretion at bedtime (p < 0.05), and higher pre-sleep cognitive arousal (p < 0.01) than the LV group; HV participants did not significantly differ from those in the INS or the LV group. Increased cortisol response and elevated sympathovagal imbalance (ie, low frequency/high frequency ratio) were each significantly associated with longer nocturnal awakenings (p = 0.048, p = 0.037, respectively). Heightened blood pressure was significantly associated with prolonged sleep onset latency, and reduced total sleep time and sleep efficiency (all ps < 0.05).

CONCLUSIONS

These findings support the hyperarousal conceptualization of insomnia and indirectly suggest that increased stress reactivity and bedtime hyperarousal might represent a trait-like vulnerability in certain good sleepers. More research is warranted to validate and expand these preliminary findings.

Low vigorous physical activity is associated with increased adrenocortical reactivity to psychosocial stress in students with high stress perceptions

OBJECTIVES

The pathways by which physical activity impacts on participants' health are still not fully understood. The purpose of the present study was to go beyond existing research by combining methods from survey-based and experimental stress research, and by examining whether the potential of vigorous physical activity (VPA) to attenuate physiological and psychological stress responses is moderated by participants' subjective stress perception.

METHODS

The sample consisted of 42 undergraduate students (M=21.2±2.2 years, 52% women). Participants self-reported their stress and wore an accelerometer device for seven consecutive days. To examine differences in the adrenocortical, autonomic and psychological stress reactivity, salivary free cortisol, heart rate, state anxiety, mood and calmness were assessed prior to, during and after the Trier Social Stress Test (TSST). The cut-offs of the American College of Sports Medicine (ACSM) were used to distinguish between students below/above current VPA recommendations.

RESULTS

High levels of perceived stress combined with VPA levels below the ACSM's standards (<3×20min/week) were associated with an increased salivary cortisol response to the TSST (p<.05). No significant group differences existed for heart rate. However, students with high stress/low VPA experienced less favourable affect throughout the entire testing session (p<.05).

CONCLUSIONS

Our study suggests that VPA has a high stress-protective potential among undergraduate students with high stress levels. Our findings highlight that promoting VPA in young adults seems to be a promising strategy to increase physiological and psychological stress resilience.