Salivary cortisol concentrations before and after carbon-dioxide inhalations in children

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.

Stress reactivity in healthy child offspring of parents with anxiety disorders

Several studies suggest that anxiety disorders (AD) involve dysregulation of the autonomic nervous system (ANS) and hypothalamic-pituitary (HPA) axis. However, it is unknown if alterations in these biological systems are premorbid markers of AD risk or a state-dependent feature of anxiety. This study examined ANS and HPA-axis response to a laboratory stressor in healthy child offspring of parents with (n = 55) and without (n = 98) a history of AD. High frequency heart rate variability (HF-HRV) was assessed during sitting and standing baseline conditions and during a speech task where participants remained standing. Salivary cortisol was measured at baseline and at 15, 30, 45 and 60 min post-speech. Subjective anxiety was assessed with a visual analogue scale. Children of parents with AD displayed reduced HRV and a blunted cortisol response to the speech task compared to children of non-anxious parents. No risk group effect was found for anxiety ratings. These preliminary data suggest that healthy children of anxious parents exhibit altered stress reactivity to an acute laboratory stressor. Further research is needed to confirm findings and identify mechanisms that may account for altered self-regulation processes to a stressor in children at familial risk for AD.

Panic-like escape response elicited in mice by exposure to CO2, but not hypoxia

Exposure to elevated concentrations of CO₂ or hypoxia has been widely used in psychiatric research as a panic provoking stimulus. However, the use of these respiratory challenges to model panic-like responses in experimental animals has been less straightforward. Little data is available, from behavioral and endocrine perspectives, to support the conclusion that a marked aversive situation, such as that experienced during panic attacks, was evoked in these animals. We here compared the behavioral responses of male CB57BL/6 mice during exposure to 20% CO₂ or 7% O₂ and its consequence on plasma levels of corticosterone. We also evaluated whether clinically-effective panicolytic drugs affect the behavioral responses expressed during CO₂ exposure. The results showed that whereas hypoxia caused a marked reduction in locomotion, inhalation of CO₂-enriched air evoked an active escape response, characterized by bouts of upward leaps directed to the border of the experimental cage, interpreted as escape attempts. Corticosterone levels were increased 30min after either of the respiratory challenges used, but it was higher in the hypoxia group. Chronic (21days), but not acute, treatment with fluoxetine or imipramine (5, 10 or 15mg/kg) or a single injection of alprazolam (0.025, 0.05 or 0.1mg/kg), but not of the anxiolytic diazepam (0.025, 0.05 or 0.1 and 1mg/kg) reduced the number of escape attempts, indicating a panicolytic-like effect. Altogether, the results suggest that whereas hypoxia increased anxiety, exposure to 20% CO₂ evoked a panic-like state. The latter condition/test protocol seems to be a simple and validated model for studying in mice pathophysiological mechanisms and the screening of novel drugs for panic disorder.

Clinical Correlates of Carbon Dioxide Hypersensitivity in Children

OBJECTIVE

Hypersensitivity to carbon dioxide (CO₂)-enriched air may be a promising risk marker for anxiety disorders. Among adult and adolescent samples, heterogeneity in distress response to the CO₂ challenge task indexes 3 underlying classes of individuals, which distinguish between sustained and acute threat response as markers for internalizing disorders, broadly, and anxiety disorders, specifically. The present study examines latent classes in children's response to the CO₂ challenge task to clarify the association of CO₂ hypersensitivity with anxiety and internalizing symptomatology in childhood.

METHOD

Healthy children from a community twin sample (N = 538; age 9-13 years) rated anxious distress every 2 minutes while breathing air enriched to 7.5% CO₂ for 8 minutes. Latent growth mixture modeling evaluated potential classes of individuals with characteristic trajectories of distress during the task to clarify the association with internalizing disorder symptoms and related traits (e.g., anxiety sensitivity, irritability).

RESULTS

Although all participants reported increased distress during the task, interindividual heterogeneity in distress indexed 3 underlying classes: a consistently low class ("low"), a consistently high class ("high"), and participants who demonstrated markedly increased acute distress ("acute"). Compared to the low class, the high class reported greater internalizing psychopathology, whereas membership in the acute class was associated with experiencing a panic-like event during the task.

CONCLUSION

As in older individuals, 3 distinct trajectories emerged to capture interindividual heterogeneity in children's distress during the CO₂ challenge task. These classes were distinguished by clinical validators that reinforce the association of CO₂ hypersensitivity and internalizing disorder phenotypes in children.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

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.

Elucidation of neurobiology of anxiety disorders in children through pharmacological challenge tests and cortisol measurements: a systematic review

Anxiety disorders are common both in adults and children. While there have been major advances in understanding the neurobiology of anxiety disorders in adults, progress has been more limited in the elucidation of the mechanisms underlying these disorders in childhood. There is a need to delineate childhood biological models, since anxiety represents a significant clinical problem in children and is a risk factor for the subsequent development of anxiety and depression in adulthood. We conducted a review of the literature regarding pharmacological challenge tests and direct hypothalamic-pituitary-adrenal axis measurement in children with anxiety disorders, with emphasis on panic disorder and social anxiety disorder. Studies identified were contrasted with those in adult panic disorder and social anxiety disorder. Despite this broad approach few studies emerged in children, with only 22 studies meeting inclusion criteria. When contrasted with adult neurobiological models of panic disorder and social anxiety disorder, children studied showed some abnormalities which mirrored those reported in adults, such as altered baseline respiration, altered responses to CO(2) challenge tests and blunted growth hormone response to yohimbine. However, results differed from adults with panic disorder and social anxiety in some aspects of noradrenergic and serotonergic function. For endpoints studied in panic disorder children, unlike adults, displayed a lack of baseline end-tidal CO(2) abnormalities and a different hypothalamic-pituitary-adrenal pattern response under low-dose CO(2). The biology of these anxiety disorders in children may only partially mirror that of adult anxiety disorders. However, caution is required as the evidence is limited, and many studies combined patients with panic disorder and social anxiety disorder with other disorders or non-specific anxiety. Further research is required to fully understand the biology and progression of childhood anxiety disorders.

Intensive two-day cognitive-behavioral intervention decreases cortisol secretion in soldiers suffering from specific phobia to wear protective mask

RESEARCH QUESTIONS

Wearing a protective mask is compulsory for those in professions such as fire-fighters, rescue personnel and soldiers. The phobia to wear a protective mask is considered a specific claustrophobia and may become of major concern during military service. To date, no data are available with respect to the hypothalamus-pituitary-adrenocortical system activity (HPA SA) for both the so-called protective mask phobia (PMP) and its treatment. The aim of the present study was three-fold: 1) to assess HPA SA in soldiers suffering from PMP before and after intensive cognitive-behavioral treatment, 2) to compare these data with controls, and 3) to relate these data to subjective sleep.

METHODS

46 Swiss Army recruits suffering from PMP were enrolled in a two-day intensive treatment course. During initial and final assessments, saliva was sampled to analyse HPA SA via salivary cortisol; saliva samples were also gathered in the morning. For comparison, saliva samples were gathered of 39 Emergency Rescue Service (ERS) recruits. All participants also completed a questionnaire related to sleep and to anxiety.

RESULTS

Compared to controls from the ERS, among army recruits suffering from PMP, cortisol secretion was significantly higher during initial and final assessments, and in the morning. Cortisol secretion decreased from initial and final assessment. Subjectively assessed sleep was more impaired in recruits suffering from PMP compared to controls. After cognitive-behavioral treatment, all recruits suffering from PMP were able to wear the protective mask.

CONCLUSIONS

Specific phobia about wearing a protective mask is treatable via a two-day intensive course. Treatment success is reflected in modified HPA SA. Methodology and results may be transferred to treat patients suffering from sleep apnea syndrome and presenting high anxiety about wearing continuous positive airway pressure devices.

Children suffering from separation anxiety disorder (SAD) show increased HPA axis activity compared to healthy controls

RESEARCH QUESTIONS

Separation anxiety disorder (SAD) is one of the most common mental disorders in childhood, and one of the earliest emerging. Little is known about the association between SAD and the hypothalamic-pituitary-adrenocortical (HPA) axis activity. Therefore, the present study aimed at investigating this association in children suffering from separation anxiety compared to healthy controls.

METHODS

A total of 31 children with diagnosed SAD (mean age: 8.45; 17 females, 14 males) and 25 healthy controls (HC; mean age: 9.74; 12 females, 13 males) took part in the study. All participants underwent psycho-physiological testing for HPA axis challenge. Testing consisted of a separation and a social exposure paradigm. Saliva samples to assess HPA axis-related cortisol secretion were gathered in parallel.

RESULTS

Compared to healthy controls, children with SAD showed greatly increased HPA axis activity, as reflected by an increased cortisol secretion throughout the entire period of investigation. The rise of cortisol was already observed in anticipation of, but not following the separation paradigm. No gender-related differences of cortisol secretion were observed.

CONCLUSIONS

Separation anxiety disorder (SAD) in children is reflected in greatly increased HPA axis activity. Compared to healthy controls, children with SAD showed increased cortisol values from the beginning of, and throughout, the entire investigation. This pattern of results suggests that both the anticipation of a separation and a persistent hyperactivity of the HPA axis system leads to an increased cortisol secretion.

Sex differences in the association between cortisol concentrations and laboratory pain responses in healthy children

BACKGROUND

Research in adult populations has highlighted sex differences in cortisol concentrations and laboratory pain responses, with men exhibiting higher cortisol concentrations and reduced pain responses compared with women. Yet, less is known about the relationship of cortisol concentrations to pain in children.

OBJECTIVE

This study examined associations between sex, cortisol, and pain responses to laboratory pain tasks in children.

METHODS

Salivary cortisol samples from subjects aged 8 to 18 years were obtained at baseline after entering the laboratory (SCb), after the completion of all pain tasks (SC1), and at the end of the session (SC2), 20 minutes later. Blood cortisol samples were also taken after completion of the pain tasks (BC1) and at the end of the session (BC2), 20 minutes later. Subjects completed 3 counterbalanced laboratory pain tasks: pressure, heat, and cold pressor tasks. Pain measures included pain tolerance, and self-reported pain intensity and unpleasantness for all 3 tasks.

RESULTS

The study included 235 healthy children and adolescents (119 boys, 116 girls; mean age, 12.7 years; range, 8-18 years; 109 [46.4%] were in early puberty; 94 [40.0%] white). Salivary and blood cortisol levels were highly correlated with each other. Salivary cortisol levels for the total sample and for boys and girls declined significantly from SCb to SC1 (P < 0.01), although there were no significant changes from SC1 to SC2. No significant sex differences in salivary or blood cortisol levels were evident at any assessment point. Separate examination of the cortisol-laboratory pain response relationships by sex (controlling for age and time of day) suggested different sex-specific patterns. Higher cortisol levels were associated with lower pain reactivity (ie, increased pressure tolerance) among boys compared with girls at SC1, SC2, and BC1 (SC1: r = 0.338, P = 0.003; SC2: r = 0.271, P = 0.020; and BC1: r = 0.261, P = 0.026). However, higher cortisol levels were related to higher pain response (ie, increased cold intensity [BC2: r = 0.229, P = 0.048] and unpleasantness [BC1: r = 0.237, P = 0.041]) in girls compared with boys.

CONCLUSIONS

These findings suggest important sex differences in cortisol-pain relationships in children and adolescents. Cortisol levels were positively associated with increased pain tolerance in boys and increased pain sensitivity in girls.

Associations between common arginine vasopressin 1b receptor and glucocorticoid receptor gene variants and HPA axis responses to psychosocial stress in a child psychiatric population

On the one hand, a suitable response to daily stressors is crucial for adequate functioning in any natural environment. On the other hand, depending on the individual's genetic makeup, prolonged stress that is accompanied by an inappropriate level of responsiveness may lead to physiological and psychiatric disorders. Several psychiatric conditions have been linked with stress and alterations in hypothalamic-pituitary-adrenal (HPA) activity. While stress is a general phenomenon, illness is only seen in a proportion of individuals, suggesting that genetic factors may play a role in the ability to cope with stress. In children, relatively little research has been conducted to determine the impact of genetic factors on the variability in HPA axis functioning. In the present exploratory investigation, 106 prepubertal children were studied to estimate the impact of four glucocorticoid receptor gene (NR3C1) polymorphisms (NR3C1-1 [rs10482605], ER22/23EK [rs6190], N363S [rs6195], N766N [rs6196]) and five arginine vasopressin (AVP) receptor 1b gene (AVPR1b) polymorphisms (AVPR1b_s1 [rs28536160], AVPR1b_s2 [rs28373064], AVPR1b_s3 [rs33976516], AVPR1b_s4 [rs33985287], AVPR1b_s5 [rs33933482]) on cortisol responses after a psychosocial stress test (public speaking task). ER22/23EK carriers had significantly lower cortisol responses to psychosocial stress compared with noncarriers. These findings provide evidence for the relevance of the ER22/23EK polymorphism in childhood HPA axis regulation. However, the small number of ER22/23EK subjects does not allow us to draw definitive conclusions about the genotypic effect.

Sex differences in salivary cortisol in response to acute stressors among healthy participants, in recreational or pathological gamblers, and in those with posttraumatic stress disorder

Sex differences in incidence and severity of some stress-related, neuropsychiatric disorders are often reported to favor men, suggesting that women may be more vulnerable to aberrant hypothalamic-pituitary-adrenal (HPA) axis responses to stress. In this review, we discuss several investigations that we, and others, have conducted assessing salivary cortisol as a measure of HPA function. We have examined basal cortisol among healthy men and women and also following acute exposure to stressors. Among healthy participants, men had higher basal cortisol levels than did women. In response to acute stressors, such as carbon dioxide or noise, respectively, cortisol levels were comparable between men and women or higher among women. We have also examined cortisol levels among those with problem eating, gambling, or posttraumatic stress disorder (PTSD). Women with restrained eating habits have higher basal cortisol levels than do women without restrained eating habits. Pathological gamblers have more aberrant stress response to gambling stimuli than do recreational gamblers, and these effects are more prominent among men than women. Men who have motor vehicle accident related PTSD, demonstrate more aberrant cortisol function, than do their female counterparts. Although these sex differences in cortisol seem to vary with type of stress exposure and/or pathophysiological status of the individual, other hormones may influence cortisol response. To address this, cortisol levels among boys and girls with different stress-related experiences, will be the subject of future investigation.

Hypothalamic-pituitary-adrenal axis dysregulation in depressed children and adolescents: a meta-analysis

Research findings on the hypothalamic-pituitary-adrenal (HPA) axis and pediatric depression reflect a variety of methodological approaches that tap different facets of HPA-axis functions. Partly owing to the methodological heterogeneity of studies, descriptive reviews of this area have produced inconsistent conclusions. Therefore, we conducted formal meta-analyses of pertinent studies in order to advance our understanding of HPA-axis dysregulation in pediatric depression. We examined: (a) 17 published studies of HPA-axis response to the dexamethasone suppression test (DST) in depressed youth (DST; N=926) and (b) 17 studies of basal HPA-axis functioning (N=1332). We also examined descriptively studies that used corticotropin-releasing hormone (CRH) infusion, and those that used psychological probes of the HPA-axis. The global standardized mean effect size difference in HPA-axis response to the DST between depressed and non-depressed youth was 0.57, z=4.18, p<0.01. The global standardized mean difference effect size in basal HPA-axis functioning was 0.20, z=4.53, p<0.01. Age, sex, timing of sampling, dexamethasone dosage, or type of control group was not a significant source of variability for the DST or basal studies. In addition, when compared to non-depressed peers, depressed youth have a normative response to CRH infusion but an overactive response to psychological stressors. In conclusion, the HPA-axis system tends to be dysregulated in depressed youth, as evidenced by atypical responses to the DST, higher baseline cortisol values, and an overactive response to psychological stressors. This pattern of dysregulation suggests anomalies within the axis's negative feedback system and CRH production, but intact pituitary and adrenal sensitivity.

A critical review of the empirical literature on the relation between anxiety and puberty

The current paper critically reviews the empirical literature focused on the association between puberty and anxiety. A detailed review of more than 45 empirical articles is provided. There is some evidence that among girls, but not boys, a more advanced pubertal status (controlling for age) is associated with higher reported anxiety symptoms. Also among girls, earlier pubertal timing is linked to higher anxiety scores. It is unclear whether early puberty may lead to increased anxiety or if high anxiety influences pubertal timing. With respect to hormones, there were relatively few significant associations for girls, although this literature is very small. Among boys, several studies reported positive associations between both gonadal and adrenal hormones and anxiety. The direction of effect for these finding is also unstudied. The primary limitation of the hormone-anxiety literature pertains to the absence of pubertal measures in samples of youth in which hormones are measured. The paper concludes with a comprehensive examination of the methodological strengths and weaknesses of the literature and recommendations for future work.

Associations between HPA axis functioning and level of anxiety in children and adolescents with an anxiety disorder

The hypothalamus-pituitary-adrenal (HPA) axis becomes active in response to stress. Hence, increased levels of anxiety in children and adolescents may be associated with changes in HPA-axis functioning. The aim of this study was to test if level of anxiety or specific anxiety disorders were associated with basal HPA axis activity in children and adolescents with an anxiety disorder. In 99 8- to 16-year-olds with an anxiety disorder, basal cortisol levels were assessed. It was tested if (1) cortisol levels correlated with the level of self-reported anxiety and (2) if cortisol levels were different for individuals with different anxiety disorders. In girls, low levels of anxiety were associated with a stronger rise in early morning cortisol concentrations. In both boys and girls, harm avoidance predicted low cortisol concentrations after awakening. Separation anxiety and physical anxiety symptoms predicted cortisol concentrations at noon. Differences between individuals with different anxiety disorders were not found. More research is needed regarding mechanisms that explain the associations that were found, and to investigate if treatment may influence HPA axis functioning in children and adolescents with an anxiety disorder.

Measurement and meaning of salivary cortisol: a focus on health and disease in children

Measurement of salivary cortisol can provide important information about hypothalamic-pituitary-adrenal (HPA) axis activity under normal conditions and in response to stress. However, there are many variables relating to the measurement of cortisol in saliva which may introduce error and therefore may render difficult the comparison and interpretation of data between, and within, laboratories. This review addresses the effects of gender, age, time and location of sampling, units of measurement, assay conditions and compliance with the protocol, all of which have the potential to impact upon the precision, accuracy and reliability of salivary cortisol measurements in the literature. Some of these factors are applicable to both adults and children, but the measurement of salivary cortisol in children introduces aspects of unique variability which demand special attention. The specific focus of this review is upon the somewhat neglected area of methodological variability of salivary cortisol measurement in children. In addition to these methodological issues, the review highlights the use of salivary cortisol measurements to provide information about HPA axis dysfunction associated with psycho- and patho-physiological conditions in children. Novel applications for salivary cortisol measurements in future research into HPA axis activity in children are also discussed.

Panic comorbidity with bipolar disorder: what is the manic-panic connection?

CONTEXT

Bipolar/panic comorbidity has been observed in clinical, community and familial samples. As both are episodic disorders of affect regulation, the common pathophysiological mechanism is likely to involve deficits in amygdala-mediated, plasticity-dependent emotional conditioning.

EVIDENCE

Neuronal genesis and synaptic remodeling occur in the amygdala; bipolar and panic disorders have both been associated with abnormality in the amygdala and related structures, as well as in molecules that modulate plasticity, such as serotonin, norepinephrine, brain-derived neurotrophic factor (BDNF) and corticotrophin releasing factor (CRF). These biological elements are involved in behavioral conditioning to threat and reward.

MODEL

Panic attacks resemble the normal acute fear response, but are abnormally dissociated from any relevant threat. Abnormal reward-seeking behavior is central to both manic and depressive syndromes. Appetites can be elevated or depressed; satisfaction of a drive may fail to condition future behavior. These dissociations may be the result of deficits in plasticity-dependent processes of conditioning within different amygdala subregions.

CONCLUSIONS

This speculative model may be a useful framework with which to connect molecular, cellular, anatomic and behavioral processes in panic and bipolar disorders. The primary clinical implication is that behavioral treatment may be critical to restore function in some bipolar patients who respond only partially to medications.

Neuroendocrine and behavioural responses to CO2 inhalation in central versus peripheral autonomic failure

Multiple system atrophy (MSA) and pure autonomic failure (PAF) represent distinct pathological models of autonomic failure in humans. We have investigated the neuroendocrine, behavioural and autonomic cardiovascular responses to the 35% CO2 challenge. Nine patients with MSA, nine with PAF and five control subjects received a single breath of 35% CO2. Peripheral autonomic failure (i.e., PAF) was associated with significantly lower resting noradrenaline levels. All groups demonstrated a significant pressor response to CO2. In controls, the mean pressor response was +60.2 mm Hg, which was significantly smaller in both the PAF (+26.8 mm Hg, P < 0.01) and MSA (+18.3 mm Hg, P < 0.001) patients. In addition, the onset of the response was significantly delayed in both MSA (140.2 s) and PAF (154.2 s) patients compared with controls (32.4 s, P = 0.04 and P = 0.03, respectively). Noradrenaline levels increased only in controls. Central autonomic impairment (i.e., MSA) was associated with lower cortisol release (+8.8% in MSA compared with +35.2% in control and +23.7% in PAF) and fewer somatic symptoms of emotional arousal. Both MSA and PAF exhibit marked sympathetic autonomic impairment, however, residual (albeit differing) sympathetic pathways can still maintain a partial cardiovascular response. A central autonomic lesion, however, also appears to be associated with blunting of both cortisol and emotional responses to this stress paradigm.

Effects of the cortisol synthesis inhibitor metyrapone on the response to carbon dioxide challenge in panic disorder

Despite the well-known association between the hypothalamic-pituitary-adrenal (HPA) axis and normal fear, it is still unclear (a) to what extent corticotropin releasing hormone (CRH) or cortisol itself mediates fear responses, and (b) to what extent the HPA axis also affects panic disorder. The carbon-dioxide (CO2) challenge has been proposed as a model for panic. Participants received the cortisol synthesis inhibitor metyrapone 30 mg/kg of body weight once and placebo once, with 1 week between challenges, at 2300 h. The following morning, blood was taken for cortisol and ACTH levels, and then participants inhaled a single vital capacity inhalation of 35% CO2 and 65% oxygen. Before and after the inhalation, participants completed an inventory of the 13 DSM-IV symptoms of panic and the NIMH questionnaire of psychological and physical symptoms. Eight healthy controls and 14 patients with panic disorder completed the protocol. As expected, CO2 increased measures of anxiety, and metyrapone lowered cortisol and increased ACTH levels. Prechallenge anxiety was modestly lowered by metyrapone, but response to CO2 was not affected. Cortisol and ACTH levels before challenge partly predicted the response to CO2. The results support an anxiogenic role for cortisol in stress, and suggest that the pathophysiological mechanism that mediates CO2-induced panic differs from those underlying other kinds of anxiety.

Twenty-four-hour cortisol secretion patterns in prepubertal children with anxiety or depressive disorders

BACKGROUND

Previous studies found few abnormalities in hypothalamic-pituitary-adrenal (HPA) axis function in prepubertal children with anxiety or depressive disorders. In this study, we combined data from two independent, consecutive studies to achieve a larger sample size. Our goal was to identify potential alterations in the circadian pattern of cortisol secretion in anxious or depressed children.

METHODS

A total of 124 prepubertal subjects from two independent samples (76 with major depressive disorder, 31 with anxiety disorders, and 17 healthy control subjects) were studied. Blood samples collected for cortisol at hourly intervals over a 24-hour period were examined. Analyses were performed aligning cortisol samples by clock-time. Additional analyses aligning samples by sleep-onset time were performed with a subsample of subjects.

RESULTS

In the combined sample, significant findings emerged that were previously undetected. Anxious children exhibited significantly lower nighttime cortisol levels and an initially sluggish rise in cortisol during the nighttime when compared with depressed and healthy control children. In contrast, depressed children did not show a clear-cut pattern of differences compared with healthy control children.

CONCLUSIONS

Anxious children seem to exhibit an altered pattern of nighttime cortisol secretion, with an initially sluggish or delayed nocturnal rise before reaching similar peak levels of cortisol near the time of awakening. These findings suggest subtle alterations in HPA axis function in prepubertal children with anxiety disorders.

Does the brain noradrenaline network mediate the effects of the CO2 challenge?

The inhalation of carbon dioxide (CO2) is commonly used in patients and volunteers as a means of producing anxiety or panic. It is generally believed that patients with panic disorder are more vulnerable to the effects of CO2 than patients with other anxiety disorders or healthy volunteers and there is speculation and debate as to the mechanism for this apparent sensitivity. Recent work from our group has shown that a single inhalation of 35% CO2 activates the hypothalamic-pituitary-adrenocortical (HPA) axis, increases blood pressure (BP) and increases subjective fear responses in healthy volunteers. Correlation analyses reveal a relationship between the changes in BP and the cortisol increase. These findings led us to postulate that a common mechanism may mediate these and the subjective responses to inhalation of CO2. We propose that the noradrenergic system, particularly the locus coeruleus (LC), but including the A1 and A2 cell groups, may be a key mediator of these responses. This article examines the evidence and discusses the results of studies from our laboratory in relation to a neuroanatomical model centring on the LC.