Association between Cold Face Test-induced vagal inhibition and cortisol response to acute stress

Loneliness during the post-confinement period: The significance of social living conditions for stress biomarkers and memory

In the aftermath of the COVID-19 lockdown, concerns about the impact of loneliness and reduced social interactions on mental health have arisen. This study explored the repercussions of post-lockdown social restrictions across psychological (loneliness, perceived stress, and depressive symptoms), biological (hair cortisol and cardiovascular activity), and cognitive dimensions (subjective memory complaints and working, declarative, and prospective memory), with a specific emphasis on perceived loneliness and the living situation. The study included 45 students: 23 (mean age = 25.69 years) in the Alone Group (AG), who experienced significant family changes and international relocation, and 22 (mean age = 25.50 years) in the Not Alone Group (NAG), who maintained their nuclear family and did not move from their home country. We assessed heart rate variability (HRV) before, during, and after immediate memory evaluations using time-domain (the square root of the mean, RMSSD) measures. The analysis revealed no significant group differences in telematic contact with family and friends, perceived stress, or depression. However, the AG participants reported fewer face-to-face interactions and greater perceived loneliness compared to the NAG. Additionally, the AG group exhibited slightly higher hair cortisol levels and worse working memory (WM) and prospective memory (PM) performance. Importantly, no significant associations were observed between memory outcomes and stress biomarkers. However, a significant interaction effect of loneliness in the relationship between hair cortisol levels and PM was found. That is, hair cortisol concentrations were negatively related to PM when participants perceived high and moderate loneliness. This interaction was absent in the working and declarative memory domains. In summary, these findings underscore the intricate interplay between loneliness, cortisol, and memory, emphasizing the need for comprehensive research on the complex mechanisms governing these multifaceted relationships.

The microbiota-gut-brain axis in stress and depression

Humans and animals are evolved to have instinctive physiological responses to threats. The perception of threat by the brain triggers a multitude of changes across the brain and body. A large body of research have demonstrated that our hardwired survival instinct, the stress response, can become maladaptive and promote major depressive disorders and other neuropsychiatric impairments. However, gaps in our understanding of how chronic stress contributes to depression and mental disorders suggest that we also need to consider factors beyond the biology of the host. The unravelling of the structure and function of microorganisms that humans and animals are host to have driven a paradigm shift in understanding the individual as a collective network composed of the host plus microbes. Well over 90% of bacteria in the body reside in the large intestines, and these microbes in the lower gut function almost like an organ in the body in the way it interacts with the host. Importantly, bidirectional interactions between the gut microbiota and the brain (i.e., the two-way microbiota-gut-brain axis) have been implicated in the pathophysiology of mental disorders including depression. Here, in summarizing the emerging literature, we envisage that further research particularly on the efferent brain-gut-microbiota axis will uncover transformative links in the biology of stress and depression.

Vagus activation by Cold Face Test reduces acute psychosocial stress responses

Chronic stress is linked to dysregulations of the two major stress pathways-the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, which could for example result from maladaptive responses to repeated acute stress. Improving recovery from acute stress could therefore help to prevent this dysregulation. One possibility of physiologically interfering with an acute stress reaction might be provided by applying a cold stimulus to the face (Cold Face Test, CFT) which activates the parasympathetic nervous system (PNS), leading to immediate heart rate decreases. Therefore, we investigated the use of the CFT protocol as an intervention to reduce acute stress responses. Twenty-eight healthy participants were exposed to acute psychosocial stress via the Montreal Imaging Stress Task (MIST) in a randomized between-subjects design while heart rate (HR), heart rate variability (HRV), and salivary cortisol were assessed. While both groups were equally stressed during the procedure, participants with CFT intervention showed better recovery, indicated by significant ([Formula: see text]) differences in HR(V). We additionally found a significantly ([Formula: see text]) lower cortisol response to the MIST and less overall cortisol secretion in the CFT condition. Both findings indicate that the CFT can successfully stimulate the PNS and inhibit the HPA axis. To the best of our knowledge, our experiment is the first to successfully use the CFT as a simple and easy-to-apply method to modify biological responses to acute stress.

Higher Resting Cardiovagal Activity Predicts Larger Decrease of Depressive Symptoms in Inpatients Treated for Stress-Related Depression

Abstract. Depression is one of the most prevalent mental disorders, with treatment outcomes generally being unsatisfactory. The identification of outcome predictors could contribute to improving diagnosis, treatment, and outcome. Heart rate variability (HRV), an index of cardiovagal activity, has been proposed as a potential correlate of depression as well as a predictor of treatment effectiveness. The aim of the present study was to examine if HRV at baseline could predict the outcome of inpatient treatment for stress-related depressive disorder (SRDD). Depressive symptoms of n = 57 inpatients with an SRDD, who were treated in a specialized burnout ward, were assessed using the Beck Depression Inventory (BDI) at the beginning, the end of treatment, and at 3-month follow-up. HRV (i.e., RMSSD, the root mean square of successive RR interval differences) was determined from a five-minute measurement in the supine position. RMSSD was not significantly associated with the BDI score at the beginning, end, and follow-up. Higher RMSSD was revealed to be a significant predictor of a stronger decrease in depressive severity from the beginning to the end of the treatment. Thereby, the regression model explained 7.6% of the total variance in the BDI decrease. The results revealed initial HRV to predict a larger decrease in depressive severity. Therefore, resting HRV represents a physiological resource and index of successful neurovisceral interaction, which supports inpatients in benefitting from specialized treatment.

Physiological behavior during stress anticipation across different chronic stress exposure adaptive models

Anticipation of stress induces physiological, behavioral and cognitive adjustments that are required for an appropriate response to the upcoming situation. Additional research examining the response of cardiopulmonary parameters and stress hormones during anticipation of stress in different chronic stress adaptive models is needed. As an addition to our previous research, a total of 57 subjects (16 elite male wrestlers, 21 water polo player and 20 sedentary subjects matched for age) were analyzed. Cardiopulmonary exercise testing (CPET) on a treadmill was used as the laboratory stress model; peak oxygen consumption (VO₂) was obtained during CPET. Plasma levels of adrenocorticotropic hormone (ACTH), cortisol, alpha-melanocyte stimulating hormone (alpha-MSH) and N-terminal-pro-B type natriuretic peptide (NT-pro-BNP) were measured by radioimmunometric, radioimmunoassay and immunoassay sandwich technique, respectively, together with cardiopulmonary measurements, 10 minutes pre-CPET and at the initiation of CPET. The response of diastolic blood pressure and heart rate was different between groups during stress anticipation (p = 0.019, 0.049, respectively), while systolic blood pressure, peak VO₂ and carbon-dioxide production responses were similar. ACTH and cortisol increased during the experimental condition, NT-pro-BNP decreased and alpha-MSH remained unchanged. All groups had similar hormonal responses during stress anticipation with the exception of the ACTH/cortisol ratio. In all three groups, ΔNT-pro-BNP during stress anticipation was the best independent predictor of peak VO₂ (B = 36.01, r = 0.37, p = 0.001). In conclusion, the type of chronic stress exposure influences the hemodynamic response during anticipation of physical stress and the path of hormonal stress axis activation. Stress hormones released during stress anticipation may hold predictive value for overall cardiopulmonary performance during the stress condition.

Altered Cardiovascular Reactivity to and Recovery from Cold Face Test-Induced Parasympathetic Stimulation in Essential Hypertension

Essential hypertension is associated with increased sympathetic and diminished parasympathetic activity as well as impaired reactivity to sympathetic stimulation. However, reactivity and recovery from parasympathetic stimulation in hypertension are unknown. We investigated reactivity and recovery to primarily parasympathetic stimulation by Cold Face Test (CFT) in essential hypertension. Moreover, we tested whether chronic stress modulates CFT-reactivity dependent on hypertension status. The CFT was conducted by applying a cold face-mask for 2 min in 24 unmedicated, otherwise healthy hypertensive men and in 24 normotensive controls. Systolic and diastolic blood pressure (BP) and heart rate (HR) were measured repeatedly. Chronic stress was assessed with the Trier-Inventory-for-Chronic-Stress-Screening-Scale. Hypertensives did not exhibit diastolic BP decreases after CFT-cessation (p = 0.59) as did normotensives (p = 0.002) and failed to show HR decreases in immediate response to CFT (p = 0.62) when compared to normotensives (p < 0.001). Systolic BP reactivity and recovery patterns did not differ between hypertensives and normotensives (p = 0.44). Chronic stress moderated HR (p = 0.045) but not BP CFT-reactivity (p's > 0.64) with chronically stressed normotensives showing similar HR reactivity as hypertensives. Our findings indicate impaired diastolic BP and HR reactivity to and recovery from CFT in hypertensives and a moderating effect of chronic stress on HR reactivity potentially reflecting reduced relaxation ability of the cardiovascular system.

Self-Reported Emotion Regulation Is Associated With Response to Test of Cardiac Vagal Function

Abstract. Parasympathetic function and emotional self-regulation (ESR) share neuroanatomic structures. Based on Porges’ Polyvagal Theory and the Neurovisceral Integration Model (NIM), we compared vagally mediated heart-rate variability (vmHRV) with psychometrically assessed ESR. We hypothesized that vmHRV and ESR would be associated during rest, a vagal function test, and recovery from that test. A significant association would justify the psychometric measuring of parasympathetic health, which is less burdensome than its psychophysiological assessment. Two hundred thirteen healthy males (aged: 18–26 years, M = 20.29 years) took part in the present study. They completed the Emotion Regulation Questionnaire (ERQ) and underwent the Cold Face Test (CFT) for 4 min wearing ambulatory electrocardiograms. A High frequency (HF) band was used as a measure of vmHRV before, during, and after the CFT. Associations between the HF band and ESR were analyzed with partial rank correlations. There was no significant association between ERQ scores and the response to the CFT itself. But there was an almost significant association between the ERQ scale Cognitive Appraisal and baseline vmHRV, and a significant association between Cognitive Appraisal and cardiac recovery from the CFT, that is, participants with higher scores on that ESR scale revealed a tendency to exhibit greater vmHRV during baseline and they exhibited greater vagal withdrawal during recovery from the CFT. Cognitive appraisal as a psychometrically assessed emotion regulatory process was reflected in a more flexible parasympathetic activity (i.e., better cardiac vagal health) during recovery from an exclusively physiological stressor. This lends convergent validity to self-reported emotion regulation, and justification for its use as a measure of ESR as a trait, offering further support for the Polyvagal Theory and NIM.

The relationship between affective flexibility, spontaneous emotion regulation and the response to induced stress

Effective emotion regulation contributes to adapting well to challenging situations. One of the proposed cognitive mechanisms underlying emotion regulation is cognitive flexibility in processing of affective material (i.e. affective flexibility). We investigated (n = 118) effects of affective flexibility on the response to a stressor and on spontaneous use of 'adaptive' and 'maladaptive' emotion regulation strategies. Additionally, we examined how emotion regulation influences stress reactivity and recovery. Affective flexibility was measured with a task-switching paradigm in which participants shift attention between affective and non-affective aspects of emotional material. We investigated changes in emotion and heart rate variability to a stress induction. Affective flexibility did not influence the response to stress, but less efficient shifting of attention towards affective aspects of negative information, and more efficient shifting of attention towards non-affective aspects of positive information were related to more use of maladaptive strategies. Emotion regulation strategy use had limited influence on the perceived and actual physiological response to a stress induction, but especially more use of adaptive regulation strategies reduced negative emotional reactivity. Our findings suggest that individual differences in affective flexibility have limited influence on the (acute) response to a stressful event and recovery afterwards, but do influence spontaneous use of emotion regulation strategies.

Association of salivary steroid hormones and their ratios with time-domain heart rate variability indices in healthy individuals

Background

Stress system consists of the hypothalamicpituitary-adrenal (HPA) axis and the locus caeruleus/norepinephrine-autonomic nervous system (ANS). Traditionally, HPA axis activity is evaluated by measuring its end-product cortisol, while the activity of ANS is assessed using heart rate variability (HRV) indices. Alterations in cortisol levels and HRV measures during laboratory-based stress tasks were extensively studied in previous research. However, scarce data exist on the associations of HRV measures with the levels of other adrenal steroid hormones under baseline conditions. Thus, we aimed to evaluate the activity of the HPA axis by measuring salivary cortisol, cortisone, dehydroepiandrosterone (DHEA) levels, and their ratios and to examine its association with HRV measures in a sample of healthy young and middle-aged adults.

Methods

For each participant (n=40), three data collection sessions taking place at the same time of the day were scheduled within five working days. Participants completed a self-reported questionnaire on sociodemographic and lifestyle characteristics, filled out t h e Perceived Stress Scale and State-Trait Anxiety Inventory. Also, saliva samples were collected, and physiological measures, including resting HR and HRV, were recorded during three data collection sessions.

Results

Statistically significant associations between diminished parasympathetic vagal tone evaluated by time domain HRV measures and higher salivary cortisol, lower DHEA levels, as well as decreased DHEA to cortisol ratio, were found. Also, physiological stress indicators (i.e., HRV) showed greater intraindividual stability compared with biochemical biomarkers (i.e., salivary steroid hormones) within five days.

Conclusions

Our findings suggest that both cortisol and DHEA mediate the link between two stress-sensitive homeostatic systems.

The effects of acute work stress and appraisal on psychobiological stress responses in a group office environment

BACKGROUND

The high prevalence of office stress and its detrimental health consequences are of concern to individuals, employers and society at large. Laboratory studies investigating office stress have mostly relied on data from participants that were tested individually on abstract tasks. In this study, we examined the effect of psychosocial office stress and work interruptions on the psychobiological stress response in a realistic but controlled group office environment. We also explored the role of cognitive stress appraisal as an underlying mechanism mediating the relationship between work stressors and the stress response.

METHODS AND MATERIALS

Ninety participants (44 female; mean age 23.11 ± 3.80) were randomly assigned to either a control condition or one of two experimental conditions in which they were exposed to psychosocial stress with or without prior work interruptions in a realistic multi-participant laboratory setting. To induce psychosocial stress, we adapted the Trier Social Stress Test for Groups to an office environment. Throughout the experiment, we continuously monitored heart rate and heart rate variability. Participants repeatedly reported on their current mood, calmness, wakefulness and perceived stress and gave saliva samples to assess changes in salivary cortisol and salivary alpha-amylase. Additionally, cognitive appraisal of the psychosocial stress test was evaluated.

RESULTS

Our analyses revealed significant group differences for most outcomes during or immediately after the stress test (i.e., mood, calmness, perceived stress, salivary cortisol, heart rate, heart rate variability) and during recovery (i.e., salivary cortisol and heart rate). Interestingly, the condition that experienced work interruptions showed a higher increase of cortisol levels but appraised the stress test as less threatening than individuals that experienced only psychosocial stress. Exploratory mediation analyses revealed a blunted response in subjective measures of stress, which was partially explained by the differences in threat appraisal.

DISCUSSION

The results showed that experimentally induced work stress led to significant responses of subjective measures of stress, the hypothalamic-pituitary-adrenal axis and the autonomic nervous system. However, there appears to be a discrepancy between the psychological and biological responses to preceding work interruptions. Appraising psychosocial stress as less threatening but still as challenging could be an adaptive way of coping and reflect a state of engagement and eustress.

Higher levels of Depressive Symptoms are Associated with Increased Resting-State Heart Rate Variability and Blunted Reactivity to a Laboratory Stress Task among Healthy Adults

Laboratory stress tasks induce strong changes in linear and non-linear indices of heart rate variability (HRV) among healthy adults, due to a task-induced parasympathetic withdrawal. Previous findings suggested that negative affectivity and its correlates (i.e., depressive symptoms, anxiety, hostility, type D personality, and situational stress) could profoundly affect autonomic activity. However, to date no studies considered these psychological dimensions simultaneously while trying to disentangle their acute effects on HRV during a laboratory stress task. A total of 65 healthy participants completed a battery of questionnaires and later underwent a psychosocial stress protocol, which involves a stressful and a non-stressful mental arithmetic task, with the latter serving as a control condition for the former. During the entire procedure, autonomic activity was recorded through a portable ECG device. We analysed longitudinal changes in HRV indices using Mixed Models, taking into account respiration rates and the associations between psychophysiological variables through bivariate Pearson's r (partial) correlation indices. We found significant changes in linear (e.g., HF power, RMSSD) and non-linear (e.g., Poincaré Plot and Correlation Dimension D2) HRV indices during the procedure, with the lowest point reached during the stressful mental arithmetic task. Interestingly, only depressive symptomatology was significantly and positively related to a higher resting-state HRV and to a blunted reactivity to the stress task, even after controlling for baseline values. Results suggest that healthy individuals with higher levels of depressive symptoms could experience atypical cardiovascular responses to stressful events: several speculative interpretations, considering autonomic, behavioral, and motivational dysregulations, are discussed.

Psychosocial Stress Before a Nap Increases Sleep Latency and Decreases Early Slow-Wave Activity

Sleep disturbances are an important risk factor for stress-related diseases such as burnout or depression. In particular, slow-wave activity (SWA) during sleep might be eminently relevant for optimal maintenance of mental health and cognitive functioning. In spite of the clinical importance and the pertinence of stress-related processes in everyday life, the physiological mechanisms of the association between stress, sleep, and cognition are not well-understood. In the present study, we carefully mapped the time course of the influence of a psychosocial stressor on sleep architecture and sleep-related oscillations during a midday nap. We induced stress using a psychosocial laboratory stressor, the Montreal Imaging Stress Task, vs. a neutral control task. Afterward, participants were allowed to take a 90-min nap (n = 20) or stayed awake (n = 19) and cortisol was measured via saliva samples. We hypothesized that stress would decrease sleep efficiency and SWA in a time-dependent manner, with impairing effects on cognitive functioning. Psychosocial stress resulted in increased cortisol levels, which were elevated throughout the study interval. In the nap group, psychosocial stress increased sleep latency, but had only minor effects on sleep architecture. Still, SWA in the first 30 min of sleep was significantly reduced, whereas alpha activity was enhanced. These effects vanished after approximately 30 min. No impairing effect on cognitive functioning occurred. Our results show that psychosocial stress before sleep has an impact on sleep latency and early SWA during sleep. In contrast to our hypothesis, the effects were rather small and short-lasting. Importantly, cognitive functioning was maintained. We conclude that the effects of psychosocial stress before a nap are possibly better compensated than previously believed.

Association between changes in heart rate variability during the anticipation of a stressful situation and the stress-induced cortisol response

Vagal activity - reflecting the activation of stress regulatory mechanisms and prefrontal cortex activation - is thought to play an inhibitory role in the regulation of the hypothalamus-pituitary-adrenal axis. However, most studies investigating the association between stress-induced changes in heart rate variability (HRV, an index of cardiac vagal tone) and cortisol have shown a non-significant relationship. It has been proposed that physiological changes observed during anticipation of a stressor allow individuals to make behavioral, cognitive, and physiological adjustments that are necessary to deal with the upcoming actual stressor. In this study, in a large sample of 171 healthy adults (96 men and 75 women; mean age = 29.98, SD = 11.07), we investigated whether the cortisol response to a laboratory-based stress task was related to anticipation-induced or stress task-induced changes in HRV. As expected, regression analyses showed that a larger decrease in HRV during the anticipation of a stress task was related to higher stress task-induced cortisol increase, but not cortisol recovery. In line with prior research, the stress task-induced change in HRV was not significantly related to cortisol increase or recovery. Our results show for the first time that anticipatory HRV (reflecting differences in stress regulation and prefrontal activity before the encounter with the stressor) is important to understand the stress-induced cortisol increase.

During stress, heart rate variability moderates the impact of childhood adversity in women with breast cancer

Childhood adversity has long-lasting neuro-biological effects that can manifest as exaggerated stress responsivity to environmental challenge. These manifestations include a dysregulated hypothalamic-pituitary-adrenocortical (HPA) axis as well as increased levels of inflammatory mediators in response to stress. In this investigation, vagal parasympathetic activity was assessed for its capacity to moderate the relationship between childhood adversity and stress responsivity (cortisol and inflammation) during an acute laboratory challenge (Trier Social Stress Test-TSST). Thirty women recently diagnosed with breast cancer underwent the TSST during which their heart rate was recorded and saliva samples collected for measurement of cortisol and the proinflammatory cytokine, IL-6. Vagal activity during the TSST was calculated as the high-frequency (HF) component of heart rate variability (HRV). Vagal activity during the TSST moderated the effect of childhood adversity on both the cortisol and the IL-6 response. Women who had lower vagal stress-reactivity during the TSST and reported greater childhood adversity showed a larger rise in cortisol and IL-6 when compared to women with lower childhood adversity. The findings demonstrate that women with exposure to childhood adversity and low vagal stress-reactivity (reduced parasympathetic activity) exhibit an elevated stress response characterized by greater cortisol and proinflammatory cytokine release. Inflammatory burden and HPA dysregulation subsequent to stress may impair cancer control.

Diurnal variation in the diving bradycardia response in young men

PURPOSE

The present study aimed to examine diurnal variation of the diving bradycardia responses on the same day.

METHODS

Eighteen young men (age 26 ± 2 years; height 174.2 ± 6.0 cm; body mass 70.2 ± 8.1 kg; body fat 18.0 ± 3.8 %; mean ± standard deviation) participated in this study. Oral temperature, heart rate variability (HRV) from 5-min of electrocardiogram data, and diving bradycardia responses were measured at 0900, 1300, and 1700 hours daily. All participants performed diving reflex tests twice in the sitting position with the face immersed in cold water (1.9-3.1 °C) and apnea at midinspiration for a minimum of 30 s and as long as possible, in consecutive order.

RESULTS

Oral temperature was found to be less in the morning (0900) than in the afternoon (1300) and evening (1700). In the frequency domain parameters of heart rate variability, the natural logarithms of high-frequency power were higher in the morning than in the evening. All participants showed bradycardia response to the two diving reflex tests. The peak values of R-R interval during the diving reflex test both for as long as possible and 30 s were longer in the morning than in the afternoon and evening.

CONCLUSION

Our results indicated that the maximal bradycardia during the diving reflex test exhibits a diurnal variation, with peak levels at morning and gradual decrease towards the evening. The HRV indexes show the same variation.

Cold Face Test-Induced Increases in Heart Rate Variability Are Abolished by Engagement in a Social Cognition Task

Abstract. The vagus nerve is a major constituent in the bidirectional relationship between the heart and the prefrontal cortex. This study investigated the role of the vagus in social cognition using the cold face test (facial cooling) to stimulate the vagus nerve and increase prefrontal inhibitory control. Heart Rate Variability (HRV) was measured to index parasympathetic outflow while social cognition ability was tested using the Reading the Mind in the Eyes Test (RMET). Healthy males (n = 25) completed the RMET under two conditions: with and without facial cooling. Results indicated that although facial cooling increased HRV at rest, there was no improvement in the RMET during the facial cooling condition. Interestingly, completing the RMET with facial cooling abolished this increase in HRV, suggesting interference along the vagal reflex arc. These results are consistent with the involvement of a common cortico-subcortical circuit in autonomic and cognitive processes, important for emotion recognition.

Blunted endocrine and cardiovascular reactivity in young healthy women reporting a history of childhood adversity

BACKGROUND

Chronic or prolonged stress exposure in childhood can alter structural and functional brain development, leading to mental and physical illness and alterations of psychobiological stress systems in adulthood. Recently, attenuation in stress reactivity of the hypothalamic-pituitary-adrenal (HPA) axis and cardiovascular system have been related to the number of adverse childhood experiences (ACEs). We set out to investigate the association of ACE duration and age of ACE occurrence on stress reactivity.

METHODS

104 women in the age range 18-25 years (mean=21.7) free of mental and physical illness underwent psychosocial stress testing with the Montreal Imaging Stress Task (MIST). Free saliva cortisol and heart rate were assessed repeatedly before and after the MIST.

RESULTS

Number of ACEs was associated with attenuated cortisol and heart rate responses to stress in a dose-response relationship. Whereas overall duration of ACEs was significantly associated with an attenuated cortisol response, the specific age of first ACE occurrence did not contribute further to the dampened stress response.

CONCLUSIONS

ACEs are associated with blunted endocrine and cardiovascular stress reactivity in young and healthy women. Adverse life events in childhood, particularly if they occur repeatedly and chronically, show a strong association with alterations in stress reactivity in adulthood, potentially predisposing for later mental or physical disorders.

Yawning, fatigue, and cortisol: expanding the Thompson Cortisol Hypothesis

Yawning and its involvement in neurological disorders has become the new scientific conundrum. Cortisol levels are known to rise during stress and fatigue; yawning may occur when we are under stress or tired. However, the link between yawning, fatigue, and cortisol has not been fully understood. Expansion of the Thompson Cortisol Hypothesis proposes that the stress hormone, cortisol, is responsible for yawning and fatigue especially in people with incomplete innervation such as multiple sclerosis. This informs our understanding of the functional importance of the brain stem region of the brain in regulating stress and fatigue.

The association between perceived emotional support, maternal mood, salivary cortisol, salivary cortisone, and the ratio between the two compounds in response to acute stress in second trimester pregnant women

OBJECTIVE

Little is known about the effect of social support on the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis during pregnancy. Moreover, when investigating the HPA axis most studies do not consider the activity of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), an enzyme within the salivary glands that inactivates cortisol to cortisone. This study explores the association between perceived emotional support and the maternal psychobiological stress response to a standardized naturalistic stressor by assessing maternal mood and the reactivity of salivary cortisol (SalF), salivary cortisone (SalE), and the SalE/(E+F) ratio as a marker of 11β-HSD2 activity.

METHODS

Repeated saliva samples and measures of maternal mood were obtained from 34 healthy second trimester pregnant women undergoing amniocentesis which served as a psychological stressor. The pregnant women additionally responded to a questionnaire of perceived emotional support and provided sociodemographic (e.g., maternal educational degree) and pregnancy-specific data (e.g., planned versus unplanned pregnancy).

RESULTS

Perceived emotional support neither showed a significant effect on mood nor on the SalF or SalE response to stress. However, a moderately strong positive association was found between perceived emotional support and SalE/(E+F) (r=.49). Additionally, the final regression analysis revealed a significant negative relationship between educational degree, planned/unplanned pregnancy and SalE/(E+F).

CONCLUSION

Findings suggest a higher metabolization of cortisol to cortisone in pregnant women with higher emotional support. In contrast, higher maternal education and unplanned pregnancy appear to be associated with decreased salivary 11β-HSD2 activity. The current study emphasizes the importance of taking the activity of 11β-HSD2 into account when examining SalF.

Neuroendocrine homeostasis after vagus nerve stimulation in rats

BACKGROUND

The vagus nerve is important in maintaining HPA axis and sympatho-adrenal system (SAS) homeostasis, however little is known about the effect of vagus nerve stimulation (VNS), as used therapeutically, on these functions. Accordingly, the effect of VNS on plasma indices of HPA axis (ACTH, corticosterone), and SAS (norepinephrine, epinephrine) function were evaluated in rats.

METHODS

Male rats, on day-0 (D0), underwent surgeries for implantation of catheters into the right jugular vein and programmable (VNP) or non-programmable (VND) neurocybernetic devices encircling the left cervical vagus. On D7, after a blood sample, the device in VNP rats was programmed to deliver 500 μs width, 0.25 mA current pulses at 20 Hz ('on' 30s, 'off' 5 min) followed by timed blood samples during the next 90 min. In acute studies, VNS was stopped at 60 min and the rats were perfused at 90 min to evaluate neuronal Fos immunoreactivity (Fos-IR). In chronic studies, the probe remained active. In these rats, the HPA axis response to airpuff-startle stressor (D17) and anterior pituitary CRF-receptor binding (D26) were evaluated.

RESULTS

During acute VNS, plasma indices of HPA axis and SAS activity, as well as Fos-IR activation pattern in brain regions known to increase after stress, were not different between VND and VNP rats. During chronic VNS, stress-induced HPA axis responses exhibited a tendency toward faster recovery to baseline in VNP rats.

CONCLUSIONS

Therapeutic VNS is not a stressor and does not compromise HPA axis or SAS homeostasis. Chronic VNS may facilitate development of efficient feedback mechanisms.

The association between the acute psychobiological stress response in second trimester pregnant women, amniotic fluid glucocorticoids, and neonatal birth outcome

The underlying biological mechanism of prenatal stress in humans is poorly understood, but maternal cortisol (F) excess seems to play an important role. In pregnant rats, acute stress causes an up-regulation of placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), an enzyme present throughout the body (e.g., placenta, salivary glands) that inactivates F to cortisone (E), thereby protecting the fetus from maternal F overexposure. Whether acute stress influences human 11β-HSD2 is unclear. We aimed to explore the association between the maternal stress reactivity and amniotic fluid F, E, and the E/(E + F) ratio as a marker of fetoplacental 11β-HSD2. The predictive value of all markers for birth outcome was investigated. We examined 34 healthy pregnant women undergoing amniocentesis, which served as a standardized, real-life stressor. F, E, and E/(E + F) were determined from a single aliquot of amniotic fluid, and from saliva samples collected repeatedly. Subjects filled out state questionnaires repeatedly and were re-examined in a control condition after notification of a normal amniocentesis result. During amniocentesis, psychological stress, salivary F (SalF), and salivary E (SalE) increased significantly, whereas SalE/(E + F) decreased. The SalF reactivity was positively associated with amniotic E, while SalE/(E + F) was inversely associated with amniotic E/(E + F). SalF and SalE predicted lower and SalE/(E + F) higher birth weight. Psychological and amniotic fluid variables were unrelated to birth outcome. Findings indicate that maternal F is inactivated to E in the human fetoplacental unit during acute stress. Increased 11β-HSD2 activity within the maternal salivary glands following acute stress may mirror further stress protective mechanisms worthwhile investigating.

Born to yawn? Understanding yawning as a warning of the rise in cortisol levels: randomized trial

BACKGROUND

Yawning consistently poses a conundrum to the medical profession and neuroscientists. Despite neurological evidence such as parakinesia brachialis oscitans in stroke patients and thermo-irregulation in multiple sclerosis patients, there is considerable debate over the reasons for yawning with the mechanisms and hormonal pathways still not fully understood. Cortisol is implicated during yawning and may link many neurological disorders. Evidence was found in support of the Thompson cortisol hypothesis that proposes cortisol levels are elevated during yawning just as they tend to rise during stress and fatigue.

OBJECTIVES

To investigate whether saliva cortisol levels rise during yawning and, therefore, support the Thompson cortisol hypothesis.

METHODS

We exposed 20 male and female volunteers aged between 18 and 53 years to conditions that provoked a yawning response in a randomized controlled trial. Saliva samples were collected at the start and again after the yawning response, or at the end of the stimuli presentations if the participant did not yawn. In addition, we collected electromyographic data of the jaw muscles to determine rest and yawning phases of neural activity. Yawning susceptibility scale, Hospital Anxiety and Depression Scale, General Health Questionnaire, and demographic and health details were also collected from each participant. A comprehensive data set allowed comparison between yawners and nonyawners, as well as between rest and yawning phases. Collecting electromyographic data from the yawning phase is novel, and we hope this will provide new information about neuromuscular activity related to cortisol levels. Exclusion criteria included chronic fatigue, diabetes, fibromyalgia, heart conditions, high blood pressure, hormone replacement therapy, multiple sclerosis, and stroke. We compared data between and within participants.

RESULTS

In the yawning group, there was a significant difference between saliva cortisol samples (t10 = -3.071, P = .01). Power and effect size were computed based on repeated-measures t tests for both the yawning and nonyawning groups. There was a medium effect size for the nonyawners group (r = .467) but low power (36%). Results were similar for the yawners group: medium effect size (r = .440) and low power (33%).

CONCLUSIONS

There was significant evidence in support of the Thompson cortisol hypothesis that suggests cortisol levels are elevated during yawning. A further longitudinal study is planned to test neurological patients. We intend to devise a diagnostic tool based on changes in cortisol levels that may assist in the early diagnosis of neurological disorders based on the data collected.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number (ISRCTN): 61942768; http://www.controlled-trials.com/ISRCTN61942768/61942768 (Archived by WebCite at http://www.webcitation.org/6A75ZNYvr).

Born to yawn? Cortisol linked to yawning: a new hypothesis

Yawning has become an interesting and curious scientific conundrum. Links between several neurological disorders can be found through the commonality of yawning episodes and contagious yawning. However, the reasons why we yawn are uncertain. Cortisol levels are known to rise during stress and fatigue; yawning may occur when we are under stress or tired. We do not know whether cortisol levels fluctuate during yawning. Potentially, yawning and cortisol levels may provide a valuable diagnostic tool and warning of untoward underlying neurological problems. A new hypothesis is proposed that links cortisol levels with yawning episodes.