The four-dimensional stress test: psychological, sympathetic-adrenal-medullary, parasympathetic and hypothalamic-pituitary-adrenal responses following inhalation of 35% CO2

Families' experiences of the Low Arousal Approach: a qualitative study

Background

Parents and carers supporting a family member presenting with behaviors of concern experience heightened stress. The Low Arousal Approach is a crisis management strategy which recognizes that stress, or physiological arousal, can be expressed through behaviors of concern. This approach aims to equip parents and carers to manage behaviors in a person-centered and non-confrontational way. There is a paucity of published research exploring the experiences of families applying this approach.

Methods

Seventeen parents who had received training in the Low Arousal Approach were interviewed to gain their perspectives on supporting their family members using this approach.

Results

Thematic analysis revealed themes relating to parental stress, which was related to external pressures, isolation, family stress, and challenges in their caring role. They described encountering negative narratives relating to self-criticism and negative judgments from others. Training in the Low Arousal Approach was related to being empowered through access to evidence, increased confidence, and increased ability to advocate for their family member's needs. Low Arousal was described as a "lifestyle" that enabled increased coping for the family unit as a whole.

Discussion/conclusion

Findings indicate that it is vitally important to recognize the views of parents and carers, and these are equally as important as the views of professionals. We must understand parents' and carers' needs in order to provide adequate support.

The role of the peripheral and central adrenergic system in the construction of the subjective emotional experience of panic

RATIONALE

Although the study of emotions can look back to over 100 years of research, it is unclear which information the brain uses to construct the subjective experience of an emotion.

OBJECTIVE

In the current study, we assess the role of the peripheral and central adrenergic system in this respect.

METHODS

Healthy volunteers underwent a double inhalation of 35% CO2, which is a well-validated procedure to induce an intense emotion, namely panic. In a randomized, cross-over design, 34 participants received either a β1-blocker acting selectively in the peripheral nervous system (atenolol), a β1-blocker acting in the peripheral and central nervous system (metoprolol), or a placebo before the CO2 inhalation.

RESULTS

Heart rate and systolic blood pressure were reduced in both β-blocker conditions compared to placebo, showing effective inhibition of the adrenergic tone. Nevertheless, the subjective experience of the induced panic was the same in all conditions, as measured by self-reported fear, discomfort, and panic symptom ratings.

CONCLUSIONS

These results indicate that information from the peripheral and central adrenergic system does not play a major role in the construction of the subjective emotion.

Copeptin response to panic provocation with CO2 in healthy adults

Repeated panic attacks are the core symptom of panic disorder and severely stressful for patients. Additional to the psychological response, the physiological symptoms are an important aspect of the experienced panic. However, data on the extent of hypothalamic-pituitary-adrenal (HPA)-axis activation during panic attacks is inconsistent. Therefore, in the present study, we aimed at investigating the stress-axis activity in more detail by including Copeptin (CoP) as a stable surrogate parameter for the vasopressinergic hypothalamic activity during experimentally induced panic attacks in healthy adults (N = 21). During a placebo-controlled panic challenge with 35% CO2 compared to normal air inhalation, we measured CoP and the peripheral effector hormones Adrenocorticotropic Releasing Hormone (ACTH) and cortisol in plasma along with the psychological response to panic anxiety. We analyzed hormonal secretion patterns, their correlations and individual panic ratings over time and explored differences between female and male participants. We found a significant CO2-induced increase of CoP plasma levels and psychological panic symptoms after CO2-administration, while no positive correlations of CoP levels with the peripheral HPA-axis hormones and with panic symptoms were present. No differences between female and male participants concerning their psychological response nor their baseline CoP levels, the release of CoP or its increase during the experiment were found. CoP could be a sensitive indicator for an organism's physiologic acute hypothalamic response during stress and panic attacks.

Manipulating Levels of Socially Evaluative Threat and the Impact on Anticipatory Stress Reactivity

Previous work suggests that relative increases in socially evaluative threat modulate the psychobiological stress response. However, few studies have compared stressors which manipulate the level of socially evaluative threat to which the participant is exposed. Here we present two studies. In the first, we assessed the integrity of an ecologically valid, laboratory stressor (direct socially evaluated multitasking) and its effects on acute psychobiological reactivity and ability to evoke an anticipatory response prior to participation. Specifically, we assessed whether the expectation and experience of direct social evaluation (multitasking while standing and facing an evaluator) evokes greater reactivity than indirect evaluation (over-the-shoulder evaluation). In the second study, we sought to replicate the findings regarding acute stress reactivity whilst extending the assessment window to assess the extent to which the stressor evokes anticipatory responses. As hypothesized, greater reactivity was observed following direct social evaluation compared with indirect observation. Increases in anxiety, heart rate and blood pressure were demonstrated across both studies and the paradigm therefore provides an ecologically valid technique for the activation of psychological and cardiovascular stress responding. Additionally, anticipation of experiencing socially evaluated multitasking led to increases in anxiety, tension, and worry prior to the event itself, supporting previous suggestions that threat anticipation may prolong the activation of stress mechanisms. In the present studies we assessed whether the expectation and experience of direct social evaluation evokes greater reactivity than indirect evaluation. The findings have demonstrated that direct social evaluation of multitasking is a more potent stressor than multitasking with indirect evaluation. Furthermore, our findings indicate that the period of anticipation of stressful events may be critical to understanding the process of stress regulation, and as such we recommend extending the sampling window to allow for the investigation of these processes.

Subjective and physiological responses to the 35% carbon dioxide challenge in healthy and non-clinical control populations: a meta-analysis and systematic review

BACKGROUND/RATIONALE

The carbon dioxide (CO₂) challenge has been reliably used in laboratory settings as a panicogen in clinical populations. However, the magnitude of these effects on healthy and non-clinical control populations are not clear. The aim of this meta-analysis and systematic review is to provide quantitative estimates of those effects. Specifically, the current paper will evaluate the relative efficacy of the CO₂ challenge in eliciting both subjective and physiological arousal in healthy and non-clinical control populations.

METHOD

A total of 16 articles with 35 independent samples were included in the meta-analysis, while 37 studies with 74 independent samples were included in the systematic review.

RESULTS

Both the meta-analysis and systematic review found the CO₂ challenge to elicit an increase in subjective distress via self-reported anxiety and fear. Physiological responses via blood pressure and heart rate were heterogeneous in studies sampled, with no significant changes observed across studies. Moderator analyses revealed the variations in findings may be attributed to participant screening and invasive sampling.

DISCUSSION

Findings highlight the CO₂ challenge as a useful tool in the provocation of subjective distress. Implications for both the use of the CO₂ challenge and its anticipated effects in healthy and non-clinical control populations are discussed.

Subjective unpleasantness of malodors induces a stress response

Unpleasant odors impair our mood and may affect physical health, even when the odorants are not toxic. A possible cause for such negative effects is stress induced by odors; however, whether the unpleasantness itself elicited stress or not has not been clear. Thus, we examined whether unpleasantness of odors induced the stress responses of emotion, the hypothalamic-pituitary-adrenal (HPA) axis, and the sympathetic nervous system (SNS). Six experiments were conducted, where salivary cortisol or salivary alpha amylase (sAA), markers for activities of the HPA and the SNS, respectively, were measured, along with subjective ratings of odors and emotion. First, the responses to three malodors listed in the Offensive Odor Control Law in Japan were examined. While these odors were rated as unpleasant, and exposure to them increased anxiety, no response of the HPA was observed (experiment 1, n = 69). In contrast, an increase of the SNS activity was observed after exposure to two of the three malodors, while the SNS did not respond to pleasant odors (experiments 2-4, n = 35, 34 and 30). To examine the effect of unpleasantness further, the SNS response was examined while subjective unpleasantness of odors was manipulated by adding negative verbal information (experiment 5, n = 92), or by mixing in a pleasant odor (experiment 6, n = 35). The SNS responses upon inhalation of the same odorous substances were found to be dependent on whether they were perceived as unpleasant. Finally, a correlation analysis on the pooled data from experiments 2-6 showed that the odor-elicited SNS activity and anxiety were strongly correlated with perceived unpleasantness of odors. These results suggest that subjective unpleasantness of odors per se can induce the stress response of emotion and the SNS.

Competition Stress Leads to a Blunting of the Cortisol Awakening Response in Elite Rowers

Background: Anticipation of forthcoming demands is often met with biological up-regulation, for example, levels of the stress hormone cortisol are typically elevated immediately prior to an anticipated event. Similarly, the cortisol awakening response (CAR), a surge in cortisol in the period following waking, is elevated on days of anticipated demand and this is viewed as an adaptive response in the preparation for challenge. This study assessed the effects of competition as an anticipated challenge in elite rowers. Methods: Elite rowers (N = 8) were assessed during two training and two competition weekends. Each assessment involved the measurement of self-reported competitive (cognitive and somatic) anxiety and salivary diurnal cortisol across 2 days representing a preparation day prior to either a training or competition day. Competitive anxiety was measured each morning and saliva samples were provided immediately upon waking and 30 min post waking (CAR) and before bed. Results: Self-reported cognitive and somatic anxiety levels were significantly greater during the competition phase compared with training. Additionally, levels of cognitive anxiety were greater on the day of competition compared with the preparation day. CAR magnitude was significantly reduced during the competition phase compared with training; however, there were no differences between preparation and event days. Conclusions: Reduced or blunted CARs are typically observed in chronically stressed populations and are characteristic of burnout and fatigue. While an increased CAR during competition may represent an adaptive response to challenge, blunted CARs and the concomitant increases in competitive anxiety observed here indicate maladaptive responding during a period where maximized functioning is critical.

Assessing Panic: Bridging the Gap Between Fundamental Mechanisms and Daily Life Experience

Panic disorder (PD) is one of the most common psychiatric disorders. Recurrent, unexpected panic attacks (PAs) are the primary symptom and strongly impact patients’ quality of life. Clinical manifestations are very heterogeneous between patients, emphasizing the need for a dimensional classification integrating various aspects of neurobiological and psychological circuits in line with the Research Domain Criteria (RDoC) proposed by the US National Institute of Mental Health. To go beyond data that can be collected in the daily clinical situation, experimental panic provocation is widely used, which has led to important insights into involved brain regions and systems. Genetic variants can determine the sensitivity to experimental models such as carbon dioxide (CO₂) exposure and can increase the risk to develop PD. Recent developments now allow to better assess the dynamic course of PAs outside the laboratory in patients’ natural environment. This can provide novel insights into the underlying mechanisms and the influence of environmental factors that can alter gene regulation by changing DNA methylation. In this mini review, we discuss assessment of PAs in the clinic, in the laboratory using CO₂ exposure, genetic associations, and the benefits of real-life assessment and epigenetic research.

Stress Profile in Remotely Piloted Aircraft Crewmembers During 2 h Operating Mission

Emotional stability plays a key role in individual and team performance during both routine activities and management of unexpected emergencies. Using a psycho-physiological approach, the stress response was investigated in drone operators in service. Methods: Salivary α-amylase (sAA), galvanic skin response (GSR) and anxiety were assessed over a 2-h operating flight. Results: Compared to baseline values, GSR and sAA values increased in operating conditions. Moreover, these values were higher in Pilots than in Sensor Operators, indicating that their stress response was greater. These results were associated with an increase in anxiety level, highlighting a relationship between autonomic reactivity and anxiety. Conclusion: This is the first report providing experimental evidences of the stress response related to Remotely Piloted Aircraft operations.

The relationship between dlPFC activity during unpredictable threat and CO2-induced panic symptoms

Panic disorder is characterized by sudden, repeated, and unexpected attacks of intense fear and overwhelming anxiety about when another attack may strike. Patients with panic disorder and healthy individuals with a history of panic attacks show a hypersensitivity to unpredictable threats, suggesting a possible link between panic and sustained anxiety. The purpose of this study was to determine the degree to which induced symptoms of panic relate to fear and anxiety, as well as activity in the neural systems that mediate and regulate these affective states. Psychological and physiological symptoms of panic were assessed during an 8-min 7.5% CO₂ challenge task. Psychological, physiological, and neural symptoms of fear and anxiety were measured during two sessions (one psychophysiology and one functional magnetic resonance imaging where subjects experienced several blocks of no threat (N), predictable shock (P), and unpredictable shock (U; NPU threat task). We used a principle component analysis to characterize panic susceptibility (PS), and found that PS significantly predicted dorsolateral prefrontal cortex (dlPFC) activity to the unpredictable cue during the NPU threat task. When examining the weighted beta coefficients from this analysis, we observed that self-reported fear/anxiety during the CO₂ challenge negatively loaded onto dlPFC activity during the NPU task. Consistent with this observation, dlPFC activity during the unpredictable cue was also negatively correlated with anxiety during the NPU sessions. Together, these results suggest that panic symptoms and anxiety are regulated by the same prefrontal cognitive control system.

Salivary alpha-amylase and noradrenaline responses to corticotropin-releasing hormone administration in humans

Salivary alpha-amylase (sAA) is a digestive enzyme mainly responsible for the hydrolysis of starch and glycogen in the oral cavity. Since the secretion of sAA is largely under the control of the sympathetic nervous system, sAA activity is also considered to be a non-invasive marker of sympathetic activation. However, the direct association between sAA activity and other sympathetic parameters remains questionable. Therefore, we employed the corticotropin-releasing hormone (CRH) stimulation test to pharmacologically activate the sympathetic nervous system and to analyze plasma noradrenaline response together with sAA activity. Thirty-one healthy male volunteers (mean age of 25.2±3.1years) were randomized into two groups and received injections with either CRH (100μg, N=17) or placebo (0.9% NaCl, N=14). Blood samples were taken at baseline and 15, 30, 60, 120min after injection. Results showed that CRH administration increased plasma noradrenaline and cortisol concentrations, sAA activity, heart rate, as well as self-reported side effects (i.e. flushing in the facial area, heart rate changes, giddiness, malaise and restlessness) and stress perception, while plasma adrenaline levels remained unaffected. In the CRH group, the total increase of sAA activity significantly correlated with noradrenaline release, indicating that sAA activity reflects pharmacologically induced sympathetic activation.

Clinical characteristics of latent classes of CO2 hypersensitivity in adolescents and young adults

Although breathing CO₂-enriched air reliably increases anxiety, there is debate concerning the nature and specificity of CO₂ hypersensitivity to panic risk and panic disorder versus anxiety disorders and related traits broadly, particularly among adolescents and emerging adults. The present study sought to clarify the association of CO₂ hypersensitivity with internalizing conditions and symptoms among adolescents and young adults. Participants (N = 628) self-reported anxiety levels every 2 min while breathing air enriched to 7.5% CO₂ for 8 min. Growth mixture models were used to examine the structure of anxiety trajectories during the task and the association of each trajectory with dimensional and diagnostic assessments of internalizing disorders. Three distinct trajectories emerged: overall low (low), overall high (high), and acutely increased anxiety (acute). Compared to the low class, the acute class reported elevated neuroticism, anxiety sensitivity, and stress whereas the high class reported elevated anxiety symptoms, depression symptoms, neuroticism, anxiety sensitivity, and increased likelihood of an anxiety disorder diagnosis. Moreover, the acute and high classes reported experiencing a panic-like event at a higher rate than the low class while participants in the high class terminated the task prematurely at a higher rate. The present study clarifies the nature of response to CO₂ challenge. Three distinct response profiles emerged, which clarifies the manifestation of CO₂ hypersensitivity in anxiety disorders with strong, though not unique, associations with panic-relevant traits.

Re-conceptualizing stress: Shifting views on the consequences of stress and its effects on stress reactivity

BACKGROUND

The consequences of stress are typically regarded from a deficit-oriented approach, conceptualizing stress to be entirely negative in its outcomes. This approach is unbalanced, and may further hinder individuals from engaging in adaptive coping. In the current study, we explored whether negative views and beliefs regarding stress interacted with a stress framing manipulation (positive, neutral and negative) on measures of stress reactivity for both psychosocial and physiological stressors.

METHOD

Ninety participants were randomized into one of three framing conditions that conceptualized the experience of stress in balanced, unbalanced-negative or unbalanced-positive ways. After watching a video on stress, participants underwent a psychosocial (Trier Social Stress Test), or a physiological (CO2 challenge) method of stress-induction. Subjective and objective markers of stress were assessed.

RESULTS

Most of the sampled population regarded stress as negative prior to framing. Further, subjective and objective reactivity were greater to the TSST compared to the CO2 challenge. Additionally, significant cubic trends were observed in the interactions of stress framing and stress-induction methodologies on heart rate and blood pressure. Balanced framing conditions in the TSST group had a significantly larger decrease in heart rate and diastolic blood pressure following stress compared to the positive and negative framing conditions.

CONCLUSION

Findings confirmed a deficit-orientation of stress within the sampled population. In addition, results highlighted the relative efficacy of the TSST compared to CO2 as a method of stress provocation. Finally, individuals in framing conditions that posited stress outcomes in unbalanced manners responded to stressors less efficiently. This suggests that unbalanced framing of stress may have set forth unrealistic expectations regarding stress that later hindered individuals from adaptive responses to stress. Potential benefits of alternative conceptualizations of stress on stress reactivity are discussed, and suggestions for future research are made.

The impact of acute stress on hormones and cytokines, and how their recovery is affected by music-evoked positive mood

Stress and recovery from stress significantly affect interactions between the central nervous system, endocrine pathways, and the immune system. However, the influence of acute stress on circulating immune-endocrine mediators in humans is not well known. Using a double-blind, randomized study design, we administered a CO2 stress test to n = 143 participants to identify the effects of acute stress, and recovery from stress, on serum levels of several mediators with immune function (IL-6, TNF-α, leptin, and somatostatin), as well as on noradrenaline, and two hypothalamic-pituitary-adrenal axis hormones (ACTH and cortisol). Moreover, during a 1 h-recovery period, we repeatedly measured these serum parameters, and administered an auditory mood-induction protocol with positive music and a neutral control stimulus. The acute stress elicited increases in noradrenaline, ACTH, cortisol, IL-6, and leptin levels. Noradrenaline and ACTH exhibited the fastest and strongest stress responses, followed by cortisol, IL-6 and leptin. The music intervention was associated with more positive mood, and stronger cortisol responses to the acute stressor in the music group. Our data show that acute (CO2) stress affects endocrine, immune and metabolic functions in humans, and they show that mood plays a causal role in the modulation of responses to acute stress.

Clinical experimental stress studies: methods and assessment

Stress is a state of threatened homeostasis during which a variety of adaptive processes are activated to produce physiological and behavioral changes. Stress induction methods are pivotal for understanding these physiological or pathophysiological changes in the body in response to stress. Furthermore, these methods are also important for the development of novel pharmacological agents for stress management. The well-described methods to induce stress in humans include the cold pressor test, Trier Social Stress Test, Montreal Imaging Stress Task, Maastricht Acute Stress Test, CO2 challenge test, Stroop test, Paced Auditory Serial Addition Task, noise stress, and Mannheim Multicomponent Stress Test. Stress assessment in humans is done by measuring biochemical markers such as cortisol, cortisol awakening response, dexamethasone suppression test, salivary α-amylase, plasma/urinary norepinephrine, norepinephrine spillover rate, and interleukins. Physiological and behavioral changes such as galvanic skin response, heart rate variability, pupil size, and muscle and/or skin sympathetic nerve activity (microneurography) and cardiovascular parameters such as heart rate, blood pressure, and self-reported anxiety are also monitored to assess stress response. This present review describes these commonly employed methods to induce stress in humans along with stress assessment methods.

Cardiovascular System Response to Carbon Dioxide and Exercise in Oxygen-Enriched Environment at 3800 m

Background: This study explores the responses of the cardiovascular system as humans exercise in an oxygen-enriched room at high altitude under various concentrations of CO₂. Methods: The study utilized a hypobaric chamber set to the following specifications: 3800 m altitude with 25% O₂ and different CO₂ concentrations of 0.5% (C1), 3.0% (C2) and 5.0% (C3). Subjects exercised for 3 min three times, separated by 30 min resting periods in the above-mentioned conditions, at sea level (SL) and at 3800 m altitude (HA). The changes of heart rate variability, heart rate and blood pressure were analyzed. Results: Total power (TP) and high frequency power (HF) decreased notably during post-exercise at HA. HF increased prominently earlier the post-exercise period at 3800 m altitude with 25% O₂ and 5.0% CO₂ (C3), while low frequency power (LF) changed barely in all tests. The ratios of LF/HF were significantly higher during post-exercise in HA, and lower after high intensity exercise in C3. Heart rate and systolic blood pressure increased significantly in HA and C3. Conclusions: Parasympathetic activity dominated in cardiac autonomic modulation, and heart rate and blood pressure increased significantly after high intensity exercise in C3.

Norepinephrine infusion with and without alpha-adrenergic blockade by phentolamine increases salivary alpha amylase in healthy men

BACKGROUND

Mental stress reliably induces increases in salivary alpha amylase (sAA), a suggested surrogate marker for sympathetic nervous system (SNS) reactivity. While stress-induced sAA increases correlate with norepinephrine (NE) secretion, a potential mediating role of noradrenergic mechanisms remains unclear. In this study, we investigated for the first time in humans whether a NE-stress-reactivity mimicking NE-infusion with and without alpha-adrenergic blockade by phentolamine would induce changes in sAA.

METHODS

In a single-blind placebo-controlled within-subjects design, 21 healthy men (29-66 years) took part in three different experimental trials varying in terms of substance infusion with a 1-min first infusion followed by a 15-min second infusion: saline-infusion (trial-1), NE-infusion (5 μg/min) without alpha-adrenergic blockade (trial-2), and with phentolamine-induced non-selective blockade of alpha1- and alpha2-adrenergic receptors (trial-3). Saliva samples were collected immediately before, during, and several times after substance infusion in addition to blood pressure and heart rate readings.

RESULTS

Experimental trials significantly differed in sAA reactivity to substance-infusion (p=.001) with higher sAA reactivity following NE-infusion with (trial-3; p=.001) and without alpha-adrenergic-blockade (trial-2; p=.004) as compared to placebo-infusion (trial-1); sAA infusion reactivity did not differ between trial-2 and trial-3 (p=.29). Effective phentolamine application was verified by blood pressure and heart rate infusion reactivity. Salivary cortisol was not affected by NE, either with or without alpha-adrenergic-blockade.

CONCLUSIONS

We found that NE-infusion stimulates sAA secretion, regardless of co-administered non-selective alpha-adrenergic blockade by phentolamine, suggesting that the mechanism underlying stress-induced sAA increases may involve NE.

Anti-stress effects of lemon balm-containing foods

Lemon balm (Melissa officinalis) has been used historically and contemporarily as a modulator of mood and cognitive function, with anxiolytic effects following administration of capsules, coated tablets and topical application. Following a pilot study with lemon balm extract administered as a water based drink, which confirmed absorption of rosmarinic acid effects on mood and cognitive function, we conducted two similar double-blind, placebo-controlled, crossover studies. These evaluated the mood and cognitive effects of a standardised M. officinalis preparation administered in palatable forms in a beverage and in yoghurt. In each study a cohort of healthy young adults' self-rated aspects of mood were measured before and after a multi-tasking framework (MTF) administered one hour and three hours following one of four treatments. Both active lemon balm treatments were generally associated with improvements in mood and/or cognitive performance, though there were some behavioral "costs" at other doses and these effects depended to some degree on the delivery matrix.

The multitasking framework: the effects of increasing workload on acute psychobiological stress reactivity

A variety of techniques exist for eliciting acute psychological stress in the laboratory; however, they vary in terms of their ease of use, reliability to elicit consistent responses and the extent to which they represent the stressors encountered in everyday life. There is, therefore, a need to develop simple laboratory techniques that reliably elicit psychobiological stress reactivity that are representative of the types of stressors encountered in everyday life. The multitasking framework is a performance-based, cognitively demanding stressor, representative of environments where individuals are required to attend and respond to several different stimuli simultaneously with varying levels of workload. Psychological (mood and perceived workload) and physiological (heart rate and blood pressure) stress reactivity was observed in response to a 15-min period of multitasking at different levels of workload intensity in a sample of 20 healthy participants. Multitasking stress elicited increases in heart rate and blood pressure, and increased workload intensity elicited dose-response increases in levels of perceived workload and mood. As individuals rarely attend to single tasks in real life, the multitasking framework provides an alternative technique for modelling acute stress and workload in the laboratory.

Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test

Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.

Salivary alpha-amylase and cortisol responsiveness following electrical stimulation stress in obsessive-compulsive disorder patients

Salivary α-amylase (sAA) serves as a marker of sympathoadrenal medullary system (SAM) activity. Salivary AA has not been extensively studied in obsessive-compulsive disorder (OCD) patients. In the current study, 45 OCD patients and 75 healthy volunteers were assessed with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the Profile of Mood State (POMS), and the State-Trait Anxiety Inventory (STAI). Measures of heart rate variability (HRV), sAA, and salivary cortisol were also obtained following the application of electrical stimulation stress. The Y-BOCS and POMS Tension-Anxiety, Depression-Dejection, Anger-Hostility, Fatigue, and Confusion scores were significantly increased in patients with OCD compared with healthy controls. In contrast, Vigor scores were significantly decreased in patients with OCD relative to scores in healthy controls. There was no difference in HRV between the patients and the controls. Salivary AA levels in female and male OCD patients were significantly elevated relative to controls both before and after electrical stimulation. In contrast, there were no differences in salivary cortisol levels between OCD patients and controls. The elevated secretion of sAA before and after stimulation may suggest an increased responsiveness to novel and uncontrollable situations in patients with OCD. An increase in sAA might be a characteristic change of OCD.

Primitive mechanisms of trauma response: an evolutionary perspective on trauma-related disorders

The symptoms we identify and the behaviors we recognize as defenses define which symptoms we see as trauma-related. Early conceptions of trauma-related disorders focused on physical signs of distress while current ones emphasize mental symptoms, but traumatizing experiences evoke psychobiological reactions. An evolutionary perspective presumes that psychophysical reactions to traumatizing events evolved to ensure survival. This theoretical review examines several primitive mechanisms (e.g., sensitization and dissolution) associated with responses to diverse stressors, from danger to life-threat. Some rapidly acquired symptoms form without conscious awareness because severe stresses can dysregulate mental and physical components within systems ensuring survival. Varied defensive options engage specialized and enduring psychophysical reactions; this allows for more adaptive responses to diverse threats. Thus, parasympathetically mediated defense states such as freeze or collapse increase trauma-related symptom variability. Comorbidity and symptom variability confuse those expecting mental rather than psychophysical responses to trauma, and active (sympathetically mediated flight and fight) rather than immobility defenses. Healthcare implications for stress research, clinical practice and diagnostic nosology stem from the broader evolutionary view.

Interpreting Stress Responses during Routine Toxicity Studies

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic–pituitary–adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article–related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.

This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies: In-life Procedures (Section 3), Nervous System (Section 4), Endocrine System (Section 5), Reproductive System (Section 6), Clinical Pathology (Section 7), and Immune System (Section 8). The paper concludes (Section 9) with a brief discussion on Minimizing Stress-Related Effects (9.1.), and a final section explaining why Parameters routinely measured are appropriate for assessing the role of stress in toxicology studies (9.2.).

Assessing agreement between salivary alpha amylase levels collected by passive drool and eluted filter paper in adolescents with cancer

PURPOSE/OBJECTIVES

To assess the validity of filter paper (FP) against the gold standard of passive drool (PD) for collecting salivary alpha amylase as a surrogate biomarker of psychological stress in adolescents with cancer.

DESIGN

Part of a longitudinal, descriptive study of symptoms in adolescents with cancer during chemotherapy.

SETTING

A pediatric hematology/oncology treatment center.

SAMPLE

33 saliva sample pairs from nine adolescents with cancer, aged 13-18 years.

METHODS

Salivary alpha amylase was collected by PD and FP at four time points during a cycle of chemotherapy: days 1 (time 1) and 2 (time 2) of chemotherapy, day 7-10 (time 3), and day 1 of the next cycle (time 4). A random effects regression was used to assess the correlation between PD and FP values, and a Bland Altman analysis was conducted to assess agreement between the values.

MAIN RESEARCH VARIABLES

Salivary alpha amylase.

FINDINGS

The estimated correlation between PD and FP values was r = 0.91, p < 0.001. Regression results were also used to rescale FP values to the levels of the PD values because the FP values were on a different scale than the PD values. The Bland Altman analysis revealed that the agreement between the rescaled FP values and PD values was not satisfactory.

CONCLUSIONS

Eluted FP may not be a valid method for collecting salivary alpha amylase in adolescents with cancer.

IMPLICATIONS FOR NURSING

Psychological stress in adolescents with cancer may be linked to negative outcomes, such as greater symptom severity and post-traumatic stress disorder. Nurses need valid, efficient, biobehavioral measures to assess psychological stress in the clinical setting.

Physiological and affective reactivity to a 35% CO₂ inhalation challenge in individuals differing in the 5-HTTLPR genotype and trait neuroticism

The inhalation of 35% carbon dioxide (CO₂) results in an acute stress response in healthy individuals and may accordingly provide a good paradigm to examine potential vulnerability factors for stress reactivity and stress-related psychopathology. It has been proposed that CO₂ reactivity is moderated by genetic (5-HTTLPR) and personality (neuroticism) factors, yet no experimental study has investigated their effects on CO₂ reactivity simultaneously. The current study examined the singular and interactive effects of the 5-HTTLPR genotype and neuroticism in predicting the affective and physiological response to a 35% CO₂ challenge in a healthy sample of male and female students. From a large group of 771 students, 48 carriers of the low/low expressing allele (S/S, S/Lg, Lg/Lg) and 48 carriers of the high/high expressing allele (La/La) with the lowest and the highest neuroticism scores (77 females, 19 males; mean age ± SD: 20.6 ± 2 years) were selected and underwent a 35% CO₂ inhalation. Visual analogue scales for anxiety and discomfort and the Panic Symptom List were used to assess affective symptomatology, while salivary samples and heart rate were assessed to establish the physiological response. A typical pattern of responses to CO₂ was observed, characterised by increases in anxiogenic symptoms and physical panic symptomatology and a reduction in heart rate; however, no effect on salivary cortisol concentration was observed. Additionally, the CO₂ reactivity did not differ between groups divided by the 5-HTTLPR genotype or neuroticism. Findings of the current study do not support a role for singular or interactive effects of the 5-HTTLPR genotype and trait neuroticism on affective and physiological reactivity to a 35% CO₂ inhalation procedure.

Maternal mood and neuroendocrine programming: effects of time of exposure and sex

Adverse exposures that influence growth in prenatal and early postnatal periods are considered to influence vulnerability to chronic diseases via their effects on the neuroendocrine system. In humans, the assessment of the underlying mechanisms has been restricted. The present study aimed to investigate the effects of adverse early-life exposures, specifically maternal mood, on hypothlamic-pituitary-adrenal (HPA) axis, sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) responses to an acute physiological stressor. In addition, we conducted a preliminary examination into whether these effects varied by time of exposure and sex. One hundred and thity-nine individuals (mean age 15.12 years) were recruited from the ALSPAC (Avon Longitudinal Study of Parents and Children) birth cohort. Participants underwent the CO(2) stress test and indices of the PNS, SNS and HPA axis were measured. Pre-existing data on demographic and psychosocial factors of the mothers during pregnancy (18 and 32 weeks) and postnatally (8 weeks and 8 months) were extracted, as were participants' clinical and demographic data at birth. Increases in both pre- and postnatal anxiety and depression were associated with greater SNS reactivity to the stressor and slower recovery, as well as blunted HPA axis responses. Programming effects on the SNS appeared to be restricted to male offspring only. No consistent relationships were evident for any of the measures of pre-stress function. We have found preliminary evidence that both pre- and postnatal maternal anxiety and depression have sustained programming effects on the SNS and HPA axis. Effects on the SNS were restricted to male offspring.

Pupil and salivary indicators of autonomic dysfunction in autism spectrum disorder

Dysregulated tonic pupil size has been reported in autism spectrum disorder (ASD). Among the possible sources of this dysregulation are disruptions in the feedback loop between norepinephrine (NE) and hypothalamic systems. In the current study, we examined afternoon levels of salivary alpha-amylase (sAA, a putative correlate of NE) and cortisol (used to assess stress-based responses) in two independent samples of children with ASD. We found a larger pupil size and lower sAA levels in ASD, compared to typical and clinical age-matched controls. This was substantiated at the individual level, as sAA levels were strongly correlated with tonic pupil size. Relatively little diurnal variation in sAA taken in the home environment in the ASD group was also observed, while typical controls showed a significant linear increase throughout the day. Results are discussed in terms of potential early biomarkers and the elucidation of underlying neural dysfunction in ASD.

Negative emotionality, depressive symptoms and cortisol diurnal rhythms: analysis of a community sample of middle-aged males

Prior research suggests that individuals with particular personality traits, like negative emotionality, are at greater risk for adverse health outcomes. Despite bivariate associations between negative emotionality, depressive symptoms and the hypothalamic pituitary adrenal axis (HPA axis), few studies have sought to understand the biological pathways through which negative emotionality, depressive symptomatology and cortisol-one of the primary hormonal products of the HPA axis--are associated. The present study explored whether negative emotionality influenced cortisol dysregulation through current depressive symptomatology and whether negative emotionality served as a moderator of the relationship between depressive symptoms and cortisol. In the community-based Vietnam Era Twin Study of Aging, 783 male twins completed two days of cortisol saliva sampling in their natural environments. Three measures of cortisol were analyzed: waking levels, the cortisol awakening response, and the peak to bed slope. Depressive symptoms significantly mediated the associations between negative emotionality and the peak to bed slope. A 2-way interaction between depressive symptoms and negative emotionality was significant for the peak to bed slope and for waking levels of cortisol. Exploration of the interactions illustrated that depressive symptoms only affected cortisol slopes at average or high levels of negative emotionality and only affected waking levels at low levels of negative emotionality. Negative emotionality and depressive symptoms were not related to the cortisol awakening response. This is the first study to find indirect associations between negative emotionality and peak to bed cortisol slopes through depressive symptoms. These findings illustrate the complex interplay between personality characteristics, depressive symptoms and different indices of the cortisol diurnal rhythm.

Neuroticism and conscientiousness are associated with cortisol diurnal profiles in adults--role of positive and negative affect

A substantial body of research on the pathophysiology of negative health outcomes has focused on dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Maladaptive and adaptive personality features have been discussed to be associated with health outcomes. In the current study, we investigated the association of neuroticism (N) and conscientiousness (C) with diurnal cortisol levels in 102 working parents (M age=37 years; 50% female). Further, we examined the impact of daily positive and negative affect on this association. During a 6-day time-sampling phase, cortisol was measured at awakening and after that within intervals of 3h. We found a positive association of N with cortisol levels throughout the measurement period, but no association of C with daily cortisol. When accounting for daily positive and negative affect, individuals with high scores on C displayed reductions in daily cortisol concentrations that were driven by positive affect compared to individuals with low C scores. No such association emerged for N. Our findings might further elucidate the role of personality in HPA axis regulation and improve our understanding of the association of endocrine states and health outcomes.

Maternal laboratory stress influences fetal neurobehavior: cortisol does not provide all answers

OBJECTIVE

Maternal stress can have an impact on pregnancy. However, effects on fetal neurobehavior are not well understood. In this study, the effect of laboratory stress on maternal psychoneuroendocrinological response and on fetal neurobehavior was studied. Serum cortisol as a potential underlying mechanism was measured.

METHODS

Twenty-seven women made a single 1.5-h visit in their third trimester. The laboratory stressor involved an arithmetic task. Associations between maternal laboratory stress response and fetal neurobehavior were analyzed by studying 19 maternal-fetal dyads with high signal quality cardiotocograms.

RESULTS

Stress exposure changed participants stress perception (p < 0.0001). However, only half of the participants (responders) had an HPA-axis response. Fetuses responded to the stress exposure depending on their mothers' stress response: (i) there was a fetal heart rate (FHR) group effect at the level of trend (p = 0.06). Fetuses of responders had higher HR levels 20 min after the exposure (p = 0.043), (ii) there were interaction (p = 0.026) and group effects at the level of trend (p = 0.078) found for FHR short-term variation (STV). Fetuses of responders had lower FHR STV 20 min after stress exposure (p = 0.007). Cortisol as a potential underlying mechanism only seemed to be associated with short- and long-term variation of FHR.

CONCLUSIONS

An activation of the maternal stress-system could result in a child being born having a history of responding to maternal stress.

An investigation into the effects of social evaluation on cardiovascular and endocrine responses to the CO2 stress test in humans

The present study examined whether social evaluation could heighten individuals' physiological responses to the CO(2) stress test, and the hypothalamic-pituitary-adrenal (HPA) response in particular. Twenty-five healthy volunteers undertook the CO(2) test under three conditions: (i) standard CO(2) protocol, (ii) standard CO(2) protocol conducted in front of a full-length mirror (mirror) and (iii) standard CO(2) protocol conducted in front of a video camera deemed to be transmitting live images of the procedure to investigators evaluating participant performance (video). Despite counterbalancing for task order, there were significant differences in anger and depression among the conditions. Repeated measures analysis of variances (ANOVAs), controlling for these mood indices, revealed that salivary cortisol, heart rate and systolic blood pressure responses to the CO(2) test were not affected by social evaluation (i.e. mirror or video). Although the data provide no evidence that endocrine and cardiovascular responses to the CO(2) test are affected by social evaluation, the potency of the social evaluation manipulation in this study is in question. Thus, further research is warranted which includes evidence of, or instructions suggesting negative social evaluation.

Application of Psychobiological Measures in Occupational Science and Occupational Therapy Research

The authors discuss the use of psychobiological measures (i.e., biomarkers) for furthering understanding of the biological foundations supporting human occupational behavior. They explore the possible applications of psychobiological measures in research relevant to occupational therapy practice and occupational science, including the documentation of outcomes following occupational therapy intervention. Common psychobiological measures that are available and of particular interest to occupational scientists and therapists are described based on a review of research that has applied psychobiological measures. Psychobiological measures have rarely been reported in the occupational science and occupational therapy literature to date, although such measures are beginning to emerge as researchers expand their questions and methods related to occupational engagement. Psychobiological measures may provide promising insights into the effectiveness of interventions designed to improve self-regulation and more effectively manage stressors for enhancing occupational performance. These measures also may be used to increase understanding of how participation in desired occupations influences arousal levels, stress response, and overall states of well-being and productivity.

Carbon dioxide-induced anesthesia results in a rapid increase in plasma levels of vasopressin

Brief anesthesia, such as after exposure to high levels of carbon dioxide, prior to decapitation is considered a more humane alternative for the euthanasia of rodents, compared with use of decapitation alone. Studies of the levels of certain stress hormones in plasma such as corticosterone and ACTH have supported the use of this method of euthanasia in endocrinological and molecular studies. In the current study, rats were briefly exposed to a chamber filled with carbon dioxide until recumbent (20-25 sec), immediately killed via decapitation, and trunk blood collected; findings were compared with rats killed via decapitation with no exposure to carbon dioxide. RIAs were used to measure arginine vasopressin (AVP) and ACTH immunoreactivity (ir) in plasma. Whereas ACTH-ir levels remained steady after brief exposure to carbon dioxide (in accordance with results of other investigators), AVP-ir levels were increased by more than an order of magnitude. These results were confirmed by quantitative capillary-liquid chromatography-mass spectrometry, indicating this observation of rapid increase in plasma AVP-ir levels is not due to nonspecific recognition by the antibody used in the RIA. Likewise, using capillary-liquid chromatography-mass spectrometry, we observed a rapid increase in plasma oxytocin levels after carbon dioxide exposure. These surprising findings have important implications for the design and interpretation of studies involving brief carbon dioxide exposure prior to decapitation as well as those with euthanasia resulting from carbon dioxide-induced asphyxiation.

Salivary alpha-amylase as a non-invasive biomarker for the sympathetic nervous system: current state of research

Development of new biomarkers is a constantly evolving field of research endeavor in psychoneuroendocrinology. Salivary biomarkers have received special attention since they are readily accessible and easily obtained. Salivary alpha-amylase (sAA) has been proposed as a sensitive biomarker for stress-related changes in the body that reflect the activity of the sympathetic nervous system (SNS), and a growing body of research is accumulating to support the validity and reliability of this parameter. However, questions remain to be answered before sAA can be accepted as an index of SNS activity. This review describes sAA as an emerging biomarker for stress and provides an overview of the current literature on stress-related alterations in sAA. It critically discusses how sAA might reflect changes in the autonomic nervous system. Finally, current and future fields for the application of sAA measurement are outlined.

Women with diarrhoea-predominant irritable bowel syndrome show an increased pressure response to 35% carbon dioxide stress challenge

The responses to inhalation of 35% carbon dioxide (CO(2)) as a stressor were compared in female irritable bowel syndrome (IBS) patients and healthy controls to assess potential differences in cardiovascular, neuroendocrine and behavioural responses to stress. A total of 22 women (12 patients with ROME II defined diarrhoea-predominant IBS and 10 aged-matched controls) were challenged with a single vital capacity breath of 35% CO(2) (with 65% oxygen). Beat-to-beat blood pressure and heart rate were recorded prior to, during and after the inhalation. Serum cortisol concentration and behavioural ratings were measured pre- and post-inhalation. A typical pattern of responses to CO(2) was observed, characterised by a reduction in heart rate and increases in serum cortisol and anxiogenic symptoms; however, these responses did not differ between groups. Both groups also demonstrated an increase in systolic blood pressure; however, this response was significantly enhanced in IBS patients compared to healthy controls (P < 0.05). These findings demonstrate that females with diarrhoea-predominant IBS have an exaggerated pressor response to 35% CO(2) stress challenge, suggesting a more stress-responsive sympathetic nervous system.

The HPA axis in major depression: classical theories and new developments

Studies over the last 40 years have demonstrated that hyperactivity of the hypothalamic-pituitary-adrenal axis is one of the most consistent biological findings in major depression psychiatry, but the mechanisms underlying this abnormality are still unclear.

Effect of chronic elevated carbon dioxide on the expression of acid-base transporters in the neonatal and adult mouse

Several pulmonary and neurological conditions, both in the newborn and adult, result in hypercapnia. This leads to disturbances in normal pH homeostasis. Most mammalian cells maintain tight control of intracellular pH (pHi) using a group of transmembrane proteins that specialize in acid-base transport. These acid-base transporters are important in adjusting pHiduring acidosis arising from hypoventilation. We hypothesized that exposure to chronic hypercapnia induces changes in the expression of acid-base transporters. Neonatal and adult CD-1 mice were exposed to either 8% or 12% CO2for 2 wk. We used Western blot analysis of membrane protein fractions from heart, kidney, and various brain regions to study the response of specific acid-base transporters to CO2. Chronic CO2increased the expression of the sodium hydrogen exchanger 1 (NHE1) and electroneutral sodium bicarbonate cotransporter (NBCn1) in the cerebral cortex, heart, and kidney of neonatal but not adult mice. CO2increased the expression of electrogenic NBC (NBCe1) in the neonatal but not the adult mouse heart and kidney. Hypercapnia decreased the expression of anion exchanger 3 (AE3) in both the neonatal and adult brain but increased AE3 expression in the neonatal heart. We conclude that: 1) chronic hypercapnia increases the expression of the acid extruders NHE1, NBCe1 and NBCn1 and decreases the expression of the acid loader AE3, possibly improving the capacity of the cell to maintain pHiin the face of acidosis; and 2) the heterogeneous response of tissues to hypercapnia depends on the level of CO2and development.

Examination stress results in altered cardiovascular responses to acute challenge and lower cortisol

The present study examined how cardiovascular and salivary cortisol responses varied in response to an acute challenge in medical students under exam stress versus those not under exam stress. One hundred and twenty-nine medical students were randomly assigned to undertake a CO2 inhalation test either prior to an examination period (exam group) or during a regular academic period (non-exam group). Heart rate (HR) and blood pressure (BP) were measured for 5 min before and 5 min after the task, and salivary cortisol samples were collected 1 min before and 10 and 30 min after the CO2 inhalation test. Participants also completed a questionnaire measuring self-reported perceived stress. The exam group exhibited significantly higher HR reactivity following the CO2 inhalation test and slower systolic blood pressure (SBP) recovery compared with the non-exam group. The exam group also reported higher perceived stress and higher stress scores were related to higher HR reactivity following CO2 inhalation. Female students across both groups exhibited significantly lower SBP reactivity compared with male students. Salivary cortisol levels were consistently lower in the exam group. These findings indicate that ongoing natural stress alters cortisol secretion and cardiovascular responses in the face of an acute stress challenge.