Ambulatory heart rate changes in patients with panic attacks

Identification of a novel perifornical-hypothalamic-area-projecting serotonergic system that inhibits innate panic and conditioned fear responses

The serotonin (5-HT) system is heavily implicated in the regulation of anxiety and trauma-related disorders such as panic disorder and post-traumatic stress disorder, respectively. However, the neural mechanisms of how serotonergic neurotransmission regulates innate panic and fear brain networks are poorly understood. Our earlier studies have identified that orexin (OX)/glutamate neurons within the perifornical hypothalamic area (PFA) play a critical role in adaptive and pathological panic and fear. While site-specific and electrophysiological studies have shown that intracranial injection and bath application of 5-HT inhibits PFA neurons via 5-HT1a receptors, they largely ignore circuit-specific neurotransmission and its physiological properties that occur in vivo. Here, we investigate the role of raphe nuclei 5-HT inputs into the PFA in panic and fear behaviors. We initially confirmed that photostimulation of glutamatergic neurons in the PFA of rats produces robust cardioexcitation and flight/aversive behaviors resembling panic-like responses. Using the retrograde tracer cholera toxin B, we determined that the PFA receives discrete innervation of serotonergic neurons clustered in the lateral wings of the dorsal (lwDRN) and in the median (MRN) raphe nuclei. Selective lesions of these serotonergic projections with saporin toxin resulted in similar panic-like responses during the suffocation-related CO2 challenge and increased freezing to fear-conditioning paradigm. Conversely, selective stimulation of serotonergic fibers in the PFA attenuated both flight/escape behaviors and cardioexcitation responses elicited by the CO2 challenge and induced conditioned place preference. The data here support the hypothesis that PFA projecting 5-HT neurons in the lwDRN/MRN represents a panic/fear-off circuit and may also play a role in reward behavior.

Expecting the Unexpected: Predicting Panic Attacks From Mood, Twitter, and Apple Watch Data

OBJECTIVE

Panic attacks are an impairing mental health problem that affects 11% of adults every year. Current criteria describe them as occurring without warning, despite evidence suggesting individuals can often identify attack triggers. We aimed to prospectively explore qualitative and quantitative factors associated with the onset of panic attacks.

RESULTS

Of 87 participants, 95% retrospectively identified a trigger for their panic attacks. Worse individually reported mood and state-level mood, as indicated by Twitter ratings, were related to greater likelihood of next-day panic attack. In a subsample of participants who uploaded their wearable sensor data (n = 32), louder ambient noise and higher resting heart rate were related to greater likelihood of next-day panic attack.

CONCLUSIONS

These promising results suggest that individuals who experience panic attacks may be able to anticipate their next attack which could be used to inform future prevention and intervention efforts.

A Digital Therapeutic Intervention Delivering Biofeedback for Panic Attacks (PanicMechanic): Feasibility and Usability Study

BACKGROUND

Panic attacks (PAs) are an impairing mental health problem that affects >11% of adults every year. PAs are episodic, and it is difficult to predict when or where they may occur; thus, they are challenging to study and treat.

OBJECTIVE

The aim of this study is to present PanicMechanic, a novel mobile health app that captures heart rate-based data and delivers biofeedback during PAs.

METHODS

In our first analysis, we leveraged this tool to capture profiles of real-world PAs in the largest sample to date (148 attacks from 50 users). In our second analysis, we present the results from a pilot study to assess the usefulness of PanicMechanic as a PA intervention (N=18).

RESULTS

The results demonstrate that heart rate fluctuates by about 15 beats per minute during a PA and takes approximately 30 seconds to return to baseline from peak, cycling approximately 4 times during each attack despite the consistently decreasing anxiety ratings. Thoughts about health were the most common trigger and potential lifestyle contributors include slightly worse stress, sleep, and eating habits and slightly less exercise and drug or alcohol consumption than typical.

CONCLUSIONS

The pilot study revealed that PanicMechanic is largely feasible to use but would be made more so with modifications to the app and the integration of consumer wearables. Similarly, participants found PanicMechanic useful, with 94% (15/16) indicating that they would recommend PanicMechanic to others who have PAs. These results highlight the need for future development and a controlled trial to establish the effectiveness of this digital therapeutic for preventing PAs.

Is There a Characteristic Autonomic Response During Outbursts of Combative Behavior in Dementia Patients?

We sought to determine whether skin conductance level could warn of outbursts of combative behavior in dementia patients by using a wristband device. Two outbursts were captured and are reported here. Although no physiologic parameter measured by the wristband gave advance warning, there is a common pattern of parasympathetic withdrawal (increased heart rate) followed approximately 30 seconds later by sympathetic activation (increased skin conductance). In the literature, a similar pattern occurs in psychogenic non-epileptic seizures. We hypothesize that similar autonomic responses reflect similarities in pathophysiology and that physical activity may partially account for the time course of skin conductance.

Taking context to heart: Momentary emotions, menstrual cycle phase, and cardiac autonomic regulation

Emotions have long been discussed in conjunction with the autonomic nervous system. Most research on emotion-autonomic linkages does not consider sex differences or an evident underlying mechanism for sex differences: menstrual cycle phase. Further, most research is limited to cross-sectional and laboratory studies. The degree to which emotion-autonomic associations manifest in everyday life may be different and may vary by sex and, for women, by menstrual cycle phase. This study employs the ambulatory monitoring of cardiovascular measures (e.g., heart rate and heart rate variability; HRV) and concurrent emotional states (e.g., sadness, stress, anxiety, anger, and happiness) in everyday life to better characterize emotion-autonomic associations as a function of sex and menstrual cycle phase. Participants (N = 174; 87 female) ages 18 to 46 (31.23 ± 6.49) were monitored over a 5-day observation period (one 2- and one 3-day session), using an ambulatory 24-hour electrocardiogram to monitor heart rate and ecological momentary assessment to record emotions every ~30 min. Women were monitored in both the early to mid-follicular and -luteal phases and men in two comparably distanced sessions. Multilevel models indicated that across sex, negative emotions and happiness were associated with elevated heart rate. Relative to men, women exhibited an elevated heart rate and reduced HRV during reports of anger. For women, during the luteal phase, but not follicular phase, momentary sadness, stress, and anxiety predicted increased heart rate and reduced HRV. These findings demonstrate the importance of considering sex and menstrual cycle phase in research investigating emotion-autonomic linkages.

Select panicogenic drugs and stimuli induce consistent increases in tail skin flushes and decreases in core body temperature

Panic attacks (PAs) are episodes of intense fear or discomfort that are accompanied by a variety of both psychological and somatic symptoms. Panic induction in preclinical models (e.g. rats) has largely been assayed through flight and avoidance behavioral tests and cardiorespiratory activity. Yet, the literature pertaining to PAs shows that thermal sensations (hot flushes/heat sensations and chills) are also a common symptom during PAs in humans. Considering that temperature alterations are objectively measurable in rodents, we hypothesized that select panicogenic drugs and stimuli induce consistent changes in thermoregulation related to hot flushes and chills. Specifically, we challenged male rats with intraperitoneal injections of the GABAergic inverse agonist FG-7142; the α2 adrenoceptor antagonist yohimbine; the serotonin agonist D-fenfluramine, and 20% CO2 (an interoceptive homeostatic challenge). We assayed core body temperature and tail skin temperature using implanted radiotelemetry probes and tail thermistors/thermal imaging camera, respectively, and found that all challenges elicited rapid, high-amplitude (~7-9°C) increase in tail skin temperature and delayed decreases (~1-3°C) in core body temperature. We propose that thermal sensations such as these may be an additional indicator of a panic response in rodents and humans, as these panicogenic compounds or stimuli are known to precipitate PAs in persons with panic disorder.

Identifying Patterns in Complex Field Data

Abstract. Ambulatory assessment methods are well suited to examine how patients with panic disorder and agoraphobia (PD/A) undertake situational exposure. But under complex field conditions of a complex treatment protocol, the variability of data can be so high that conventional analytic approaches based on group averages inadequately describe individual variability. To understand how fear responses change throughout exposure, we aimed to demonstrate the incremental value of sorting HR responses (an index of fear) prior to applying averaging procedures. As part of their panic treatment, 85 patients with PD/A completed a total of 233 bus exposure exercises. Heart rate (HR), global positioning system (GPS) location, and self-report data were collected. Patients were randomized to one of two active treatment conditions (standard exposure or fear-augmented exposure) and completed multiple exposures in four consecutive exposure sessions. We used latent class cluster analysis (CA) to cluster heart rate (HR) responses collected at the start of bus exposure exercises (5 min long, centered on bus boarding). Intra-individual patterns of assignment across exposure repetitions were examined to explore the relative influence of individual and situational factors on HR responses. The association between response types and panic disorder symptoms was determined by examining how clusters were related to self-reported anxiety, concordance between HR and self-report measures, and bodily symptom tolerance. These analyses were contrasted with a conventional analysis based on averages across experimental conditions. HR responses were sorted according to form and level criteria and yielded nine clusters, seven of which were interpretable. Cluster assignment was not stable across sessions or treatment condition. Clusters characterized by a low absolute HR level that slowly decayed corresponded with low self-reported anxiety and greater self-rated tolerance of bodily symptoms. Inconsistent individual factors influenced HR responses less than situational factors. Applying clustering can help to extend the conventional analysis of highly variable data collected in the field. We discuss the merits of this approach and reasons for the non-stereotypical pattern of cluster assignment across exposures.

Panic Disorder Comorbidity with Medical Conditions and Treatment Implications

Panic disorder (PD) is unique among the anxiety disorders in that panic symptoms are primarily of a physical nature. Consequently, comorbidity with medical illness is significant. This review examines the association between PD and medical illness. We identify shared pathophysiological and psychological correlates and illustrate how physiological activation in panic sufferers underlies their symptom experience in the context of the fight-or-flight response and beyond a situation-specific response pattern. We then review evidence for bodily symptom perception accuracy in PD. Prevalence of comorbidity for PD and medical illness is presented, with a focus on respiratory and cardiovascular illness, irritable bowel syndrome, and diabetes, followed by an outline for potential pathways of a bidirectional association. We conclude by illustrating commonalities in mediating mechanistic pathways and moderating risk factors across medical illnesses, and we discuss implications for diagnosis and treatment of both types of conditions.

Cardiophobia: An Anxiety Disorder in Its Own Right?

Cardiophobic persons repeatedly present with complaints of chest pain and heart palpitations accompanied by fears of having a heart attack and of dying. They focus attention on their heart when experiencing stress and arousal, perceive its function in a phobic manner, and continue to believe they suffer from an organic heart problem despite repeated negative medical tests. To reduce anxiety, they seek continuous reassurance, make excessive use of medical facilities, and avoid activities believed to bring on symptoms. This article analyses the evidence for viewing cardiophobia as a phobic disorder in its own right rather than merely a problem of non-organic chest pain with some overlay of anxiety and depression. Despite some overlapping symptoms shared with persons who suffer from panic disorder, illness phobia, and extreme health anxiety, a number of central and defining features of cardiophobia are identified to differentiate cardiophobia from other anxiety disorders. An integrative model for understanding the origin and maintenance of cardiophobia (Eifert, 1990) is summarised and some treatment recommendations are derived from this model to target the central problems of persons with cardiophobia. Directions for future research are also discussed.

Etiology, triggers and neurochemical circuits associated with unexpected, expected, and laboratory-induced panic attacks

Panic disorder (PD) is a severe anxiety disorder that is characterized by recurrent panic attacks (PA), which can be unexpected (uPA, i.e., no clear identifiable trigger) or expected (ePA). Panic typically involves an abrupt feeling of catastrophic fear or distress accompanied by physiological symptoms such as palpitations, racing heart, thermal sensations, and sweating. Recurrent uPA and ePA can also lead to agoraphobia, where subjects with PD avoid situations that were associated with PA. Here we will review recent developments in our understanding of PD, which includes discussions on: symptoms and signs associated with uPA and ePAs; Diagnosis of PD and the new DSM-V; biological etiology such as heritability and gene×environment and gene×hormonal development interactions; comparisons between laboratory and naturally occurring uPAs and ePAs; neurochemical systems that are associated with clinical PAs (e.g. gene associations; targets for triggering or treating PAs), adaptive fear and panic response concepts in the context of new NIH RDoc approach; and finally strengths and weaknesses of translational animal models of adaptive and pathological panic states.

Sleep and anxiety disorders

Sleep disturbances-particularly insomnia - are highly prevalent in anxiety disorders and complaints such as insomnia or nightmares have even been incorporated in some anxiety disorder definitions, such as generalized anxiety disorder and posttraumatic stress disorder. In the first part of this review, the relationship between sleep and anxiety is discussed in terms of adaptive response to stress. Recent studies suggested that the corticotropin-releasing hormone system and the locus ceruleus-autonomic nervous system may play major roles in the arousal response to stress. It has been suggested that these systems may be particularly vulnerable to prolonged or repeated stress, further leading to a dysfunctional arousal state and pathological anxiety states, Polysomnographic studies documented limited alteration of sleep in anxiety disorders. There is some indication for alteration in sleep maintenance in generalized anxiety disorder and for both sleep initiation and maintenance in panic disorder; no clear picture emerges for obsessive-compulsive disorder or posttraumatic stress disorder. Finally, an unequivocal sleep architecture profile that could specifically relate to a particular anxiety disorder could not be evidenced; in contrast, conflicting results are often found for the same disorder. Discrepancies between studies could have been related to illness severity, diagnostic comorbidity, and duration of illness. A brief treatment approach for each anxiety disorder is also suggested with a special focus on sleep.

Do unexpected panic attacks occur spontaneously?

BACKGROUND

Spontaneous or unexpected panic attacks, per definition, occur "out of the blue," in the absence of cues or triggers. Accordingly, physiological arousal or instability should occur at the onset of, or during, the attack, but not preceding it. To test this hypothesis, we examined if points of significant autonomic changes preceded the onset of spontaneous panic attacks.

METHODS

Forty-three panic disorder patients underwent repeated 24-hour ambulatory monitoring. Thirteen natural panic attacks were recorded during 1960 hours of monitoring. Minute-by-minute epochs beginning 60 minutes before and continuing to 10 minutes after the onset of individual attacks were examined for respiration, heart rate, and skin conductance level. Measures were controlled for physical activity and vocalization and compared with time matched control periods within the same person.

RESULTS

Significant patterns of instability across a number of autonomic and respiratory variables were detected as early as 47 minutes before panic onset. The final minutes before onset were dominated by respiratory changes, with significant decreases in tidal volume followed by abrupt carbon dioxide partial pressure increases. Panic attack onset was characterized by heart rate and tidal volume increases and a drop in carbon dioxide partial pressure. Symptom report was consistent with these changes. Skin conductance levels were generally elevated in the hour before, and during, the attacks. Changes in the matched control periods were largely absent.

CONCLUSIONS

Significant autonomic irregularities preceded the onset of attacks that were reported as abrupt and unexpected. The findings invite reconsideration of the current diagnostic distinction between uncued and cued panic attacks.

Nonhomogeneous results in place learning among panic disorder patients with agoraphobia

Patients affected by panic disorder with agoraphobia (PDA) often suffer from visuo-spatial disturbances. In the present study, we tested the place-learning abilities in a sample of 31 PDA patients compared to 31 healthy controls (CTR) using the computer-generated arena (C-G Arena), a desktop-based computer program developed at the University of Arizona (Jacobs et al 1997, for further detail about the program, see http://web.arizona.edu/~arg/data.html). Subjects were asked to search the computer-generated space, over several trials, for the location of a hidden target. Results showed that control subjects rapidly learned to locate the invisible target and consistently returned to it, while PDA patients were divided in two subgroups: some of them (PDA-A) were as good as controls in place learning, while some others (PDA-B) were unable to learn the correct strategies to find the target. Further analyses revealed that PDA-A patients were significantly younger and affected by panic disorder from less time than PDA-B, indicating that age and duration of illness can be critical factors that influence the place-learning abilities. The existence of two different subgroups of PDA patients who differ in their spatial orientation abilities could provide new insight into the mechanisms of panic and open new perspectives in the cognitive-behavioral treatment of this diffuse and disabling disorder.

What is an anxiety disorder?

Initiated as part of the ongoing deliberation about the nosological structure of DSM, this review aims to evaluate whether the anxiety disorders share features of responding that define them and make them distinct from depressive disorders, and/or that differentiate fear disorders from anxious-misery disorders. The review covers symptom self-report as well as on-line indices of behavioral, physiological, cognitive, and neural responding in the presence of aversive stimuli. The data indicate that the anxiety disorders share self-reported symptoms of anxiety and fear; heightened anxiety and fear responding to cues that signal threat, cues that signal no threat, cues that formerly signaled threat, and contexts associated with threat; elevated stress reactivity to aversive stimuli; attentional biases to threat-relevant stimuli and threat-based appraisals of ambiguous stimuli; and elevated amygdala responses to threat-relevant stimuli. Some differences exist among anxiety disorders, and between anxiety disorders and depressive disorders. However, the differences are not fully consistent with proposed subdivisions of fear disorders vs. anxious misery disorders, and comparative data in large part are lacking. Given the high rates of co-morbidity, advances in our understanding of the features of responding that are shared across vs. unique to anxiety and depressive disorders will require dimensional approaches. In summary, the extant data help to define the features of responding that are shared across anxiety disorders, but are insufficient to justify revisions to the DSM nosology at this time.

Change point analysis for longitudinal physiological data: detection of cardio-respiratory changes preceding panic attacks

Statistical methods for detecting changes in longitudinal time series of psychophysiological data are limited. ANOVA and mixed models are not designed to detect the existence, timing, or duration of unknown changes in such data. Change point (CP) analysis was developed to detect distinct changes in time series data. Preliminary reports using CP analysis for fMRI data are promising. Here, we illustrate the application of CP analysis for detecting discrete changes in ambulatory, peripheral physiological data leading up to naturally occurring panic attacks (PAs). The CP method was successful in detecting cardio-respiratory changes that preceded the onset of reported PAs. Furthermore, the changes were unique to the pre-PA period, and were not detected in matched non-PA control periods. The efficacy of our CP method was further validated by detecting patterns of change that were consistent with prominent respiratory theories of panic positing a relation between aberrant respiration and panic etiology.

Panic disorder: a review of DSM-IV panic disorder and proposals for DSM-V

This review covers the literature since the publication of DSM-IV on the diagnostic criteria for panic attacks (PAs) and panic disorder (PD). Specific recommendations are made based on the evidence available. In particular, slight changes are proposed for the wording of the diagnostic criteria for PAs to ease the differentiation between panic and surrounding anxiety; simplification and clarification of the operationalization of types of PAs (expected vs. unexpected) is proposed; and consideration is given to the value of PAs as a specifier for all DSM diagnoses and to the cultural validity of certain symptom profiles. In addition, slight changes are proposed for the wording of the diagnostic criteria to increase clarity and parsimony of the criteria. Finally, based on the available evidence, no changes are proposed with regard to the developmental expression of PAs or PD. This review presents a number of options and preliminary recommendations to be considered for DSM-V.

Comparison Between the Panic Disorder with Agoraphobia Patients and Normal Controls on the Basis of Cognitions Affect and Physiology

Research using ambulatory monitoring and cognitive sampling procedures has revealed the importance of negatively biased cognitions in panic attacks and panic disorder. However, the normal population has never been investigated on the basis of these procedures and it is still unclear how patients deviate from them on the basis of negative cognitions and their interaction with affect and physiology. The present study investigated these issues by comparing 15 panic disorder patients with an equal number of normal controls. The results revealed that, although the pattern of reporting cognitions was similar, the two groups differed on type and content of the cognitions. In general, there were significant differences between the two groups for neutral and negative cognitions. Patients experienced high anxiety levels that were associated with cognitions of negative affect. There was a low frequency of reported panic attacks in the patients group. Possible reasons for the limited number of panic attacks are discussed.

Co-occurrence of Insomnia and Anxiety Disorders: A Review of the Literature

Insomnia and anxiety disorders are highly prevalent and are associated with significant impairment and disability. There is evidence that insomnia and anxiety disorders commonly co-occur, in addition to both being highly comorbid with major depressive disorder. Thus, it is important for health care providers to be familiar with the literature in this area. Therefore, the purpose of this review was to examine the empirical literature on the co-occurrence of insomnia and anxiety disorders, as well as discuss the clinical and research implications of the findings. Studies were identified through PubMed and PsycINFO searches (1975-2007) and a bibliographic review of published articles. The results from this literature review suggest that certain anxiety disorders, such as panic disorder and generalized anxiety disorder, are clearly associated with symptoms of insomnia (eg, delayed sleep onset, restless sleep). Although there are some discrepancies in the literature, the findings suggest that individuals with posttraumatic stress disorder also experience significant sleep problems (eg, middle-of-the-night insomnia, poor sleep quality, nightmares), and the presence of such problems during the early posttrauma period predicts later development of the disorder. Few empirical studies examine sleep in other anxiety disorders, and the majority of studies on insomnia and anxiety disorders in general have not examined the effects of comorbid major depressive disorder, indicating a need for additional research. Overall, the findings highlight the importance of screening for and treating anxiety symptoms when a patient presents with symptoms of insomnia and vice versa. Clearly, treatment development work on interventions that address co-occurring insomnia and anxiety disorders is greatly needed.

Sleep-based heart period variability in panic disorder with and without nocturnal panic attacks

In this paper, we investigated ambulatory sleep heart period variability in panic disorder participants with nocturnal panic (NP) compared to daytime panic attacks only. A time-derived measure of heart period variability (HPV) during sleep was significantly reduced in the NP group (n=32) relative to the daytime panic (n=17) and nonanxious (n=17) control groups. Consistent with previous work, NP participants also reported greater fear of relaxation and sleep than daytime panic and control groups. Based on a neurovisceral model of attention [Thayer, J. F., & Lane, R. D. (2000). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 61, 210-216] that predicts that decreased HPV is related to disregulated behavioral adaptation, we hypothesized that HPV measured during sleep would be most reduced in NP participants. These findings indicate that HPV is related to nocturnal panic disorder insofar as it is measured during sleep.

Psychophysiological correlates of anxiety: a single-case study

We examined the relationship between self-reported anxiety and physiological measures (blood pressure and heart rate) in a series of exposures to a feared situation of a single participant with panic disorder with agoraphobia. During each exposure, readings of heart rate, systolic blood pressure and diastolic blood pressure were taken every 20 s. Over 30 exposures, we found a near-linear relationship between anxiety and the three physiological measures. Implications of this result for usefulness of physiological measures in anxiety research and in the clinical treatment of anxiety disorders are discussed.

Sleep and anxiety disorders

Sleep disturbances commonly are associated with anxiety disorders, in particular generalized anxiety disorder, panic disorder, and posttraumatic stress disorder. Sleep loss may exacerbate and contribute to relapse of these conditions. Core features of panic disorder and posttraumatic stress disorder occur in relation to sleep (sleep panic attacks or re-experiencing nightmares). Investigation of sleep in anxiety disorders provides clues to mechanisms of arousal regulation relevant to insomnia and pathologic anxiety. Established treatments for anxiety disorders and insomnia have many overlapping components; however, optimal sequencing and integration of the approaches remain under-investigated.

Diurnal panic attacks with and without nocturnal panic attacks: are there some phenomenological differences?

OBJECTIVE: To compare nocturnal and diurnal panic attacks in a cross-sectional study and in a longitudinal prospective short-term follow-up. METHODS: We selected 57 panic disorder (PD) subjects (DSM-IV) and rated them with the Panic Disorder Severity Scale (PDSS) at baseline and after 30 days of treatment with nortriptyline, and with the Eysenck Personality Inventory and the Brown Attention Deficit Disorder (ADD) Scale at baseline. RESULTS: The sample was divided into a nocturnal and diurnal panic attack (NDPA) group - 57.9% (n = 33) - and a diurnal panic attack (DPA) group - 42.1% (n = 24). The groups showed a similar mean age at onset of PD and a pattern of prominent respiratory symptoms. The PDSS did not differ between the groups following short-term treatment (p = 0.451). There were also neither significant differences in Neuroticism (p = 0.094) and Extroversion (p = 0.269) nor in the Brown ADD Scale (p = 0.527). CONCLUSION: In our study, patients with both nocturnal and diurnal panic attacks showed similar features in their phenomenology and short-term outcome when compared to pure diurnal panic attacks patients.

Sleep disturbance in anxiety disorders

Many patients suffering from the majority of anxiety disorders complain about their sleep by reporting difficulties in initiating and maintaining it. Polysomnographic studies have shown that, in comparison to normal subjects, the sleep of patients with panic disorder is characterized by longer sleep latency, increased time awake and reduced sleep efficiency. Sleep architecture is normal and there are no significant changes in REM sleep measures. Nocturnal panic attacks are non-REM-related events and occur without an obvious trigger in 18-45% of panic disorder patients. Regarding generalized anxiety disorder, the patients complain of 'trouble sleeping' in 60-70%, while polysomnography has shown increased sleep latency and decreased sleep continuity measures. The findings in REM sleep and sleep architecture generally do not show any aberration to exist. In patients with obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD), results from the sleep laboratory do not seem to support the subjective complaints of poor sleep. The early reports of shortened REM latency in OCD could not be replicated by recent studies. A dysregulation of the REM sleep control system has been reported for patients with PTSD. Finally, no significant differences were found in all sleep parameters between social phobia patients and controls.

An integrated cognitive model of panic disorder: The role of positive and negative cognitions

One reason for the neglect of the role of positive factors in cognitive-behavioural therapy (CBT) may relate to a failure to develop cognitive models that integrate positive and negative cognitions. Bandura [Psychol. Rev. 84 (1977) 191; Anxiety Res. 1 (1988) 77] proposed that self-efficacy beliefs mediate a range of emotional and behavioural outcomes. However, in panic disorder, cognitively based research to date has largely focused on catastrophic misinterpretation of bodily sensations. Although a number of studies support each of the predictions associated with the account of panic disorder that is based on the role of negative cognitions, a review of the literature indicated that a cognitively based explanation of the disorder may be considerably strengthened by inclusion of positive cognitions that emphasize control or coping. Evidence to support an Integrated Cognitive Model (ICM) of panic disorder was examined and the theoretical implications of this model were discussed in terms of both schema change and compensatory skills accounts of change processes in CBT.

Differences between those who panic by day and those who also panic by night

This study examined the characteristics, correlates, background demographic, and personality variables associated with panic among those who panic exclusively from a waking state and those who also panic out of sleep. Participants were recruited through advertising in print media and through anxiety/panic support groups. Some group differences in the characteristics of panic and the associations between panic and other variables were found. Specifically, levels of anxiety sensitivity were higher, panic duration was longer, and panic was less strongly related to catastrophic cognitions for the group that experienced nocturnal panic. These differences are cautiously interpreted as not supporting a "strong" cognitive theory of panic initiation.

Carbon dioxide in the study of panic disorder: issues of definition, methodology, and outcome

The carbon dioxide (CO(2)) challenge paradigm has been useful for modeling panic in the laboratory. While showing promise as a technique able to promote a better understanding of the etiology of panic disorder (PD), this goal has been impeded by the lack of standardization of the challenge methodology and by uncertainty concerning the optimal definition and assessment of laboratory panic. The purpose of this paper is to highlight the impact of method variance on laboratory findings and to present recommendations for future challenge research. We begin by reviewing studies that have employed CO(2) as a stimulus for panic provocation focusing on the status of key methodological parameters between the studies and the relationship of these parameters to findings. We then make pragmatic and theoretically-based recommendations concerning approaches to methodological standardization, the establishment of a valid laboratory panic definition and the desirability of using of additional outcome measures. We conclude that although further work is needed to improve the CO(2) challenge laboratory model of panic, this paradigm can play an important role in understanding the psychopathology of PD.

Panic termination and the post-panic period

A comprehensive theory of panic must explain not only the cause(s) of episodes of panic but also why and when panic episodes terminate. Accordingly, we conducted a set of three studies on participants with panic disorder in order to investigate these aspects of panic episodes. In Study 1, we asked participants to monitor their panics prospectively, paying particular attention to the episodes' conclusions and the time period which followed. Results from Study 1 were consistent with earlier retrospective studies, showing that people engage in safety and other behaviors in an attempt to end their panics. We also collected information from the participants on beliefs about panic termination and the post-panic period. Study 2 was designed to determine if a post-panic refractory period occurs. Participants were asked to complete a hyperventilation exercise, and then to repeat the exercise a second time. Results from this study provide scant evidence of a post-panic refractory period. Study 3 was a more ecologically valid version of Study 2, in which participants were asked to re-trigger panics that occurred in their natural surroundings. Again, there was little support for a post-panic refractory period. Results are discussed in terms of cognitive-behavioral and biological theories of panic disorder.

Autonomic dysregulation in panic disorder and in post-traumatic stress disorder: application of power spectrum analysis of heart rate variability at rest and in response to recollection of trauma or panic attacks

Power spectral analysis (PSA) of heart rate variability (HRV) offers reliable assessment of cardiovascular autonomic responses, providing a 'window' onto the interaction of peripheral sympathetic and parasympathetic tone. Alterations in HRV are associated with various physiological and pathophysiological processes, and may contribute to morbidity and mortality. Previous studies of posttraumatic stress disorder (PTSD) found lower resting HRV in patients compared to controls, suggesting increased sympathetic and decreased parasympathetic tone. This article describes the analysis of HRV at rest and after psychological stress in panic disorder (PD) patients, in an enlarged sample of PTSD patients, and in healthy control subjects. Standardized heart rate (HR) analysis was carried out in 14 PTSD patients, 11 PD patients and 25 matched controls. ECG recordings were made while subjects were resting ('rest 1'), while recalling the trauma implicated in PTSD, or the circumstances of a severe panic attack, as appropriate ('recall'), and again while resting ('rest 2'). Controls were asked to recall a stressful life event during recall. While both patient groups had elevated HR and low frequency (LF) components of HRV at baseline (suggesting increased sympathetic activity), PTSD patients, unlike PD patients and controls, failed to respond to the recall stress with increases in HR and LF. HRV analysis demonstrates significant differences in autonomic regulation of PTSD and PD patients compared to each other and to control subjects. HRV analysis may augment biochemical studies of peripheral measures in these disorders.

Do panic symptom profiles influence response to a hypoxic challenge in patients with panic disorder? A preliminary report

OBJECTIVE

This study examined how panic symptom profiles affect response to a hypoxic laboratory challenge in patients with panic disorder.

METHODS

Seven patients whose naturally occurring panic attacks were characterized by prominent respiratory symptoms (Resp subgroup) were compared and contrasted with seven patients who did not report respiratory symptoms during panic attacks (NonResp subgroup). All were administered a novel 12% O2 challenge and assessed with measures of tidal volume, respiratory rate, end-tidal CO2, anxiety, and panic symptoms.

RESULTS

Although the Resp and NonResp subgroups showed equivalent increases in anxiety and panic symptoms, the Resp subgroup showed greater fluctuation in tidal volume during and after the challenge as well as overall lower levels of end-tidal CO2.

CONCLUSIONS

Our results suggest the importance of panic symptom profiles in determining respiratory responses to a hypoxic challenge in patients with panic disorder. These findings are discussed in light of current theories of panic disorder, with particular attention to respiratory disturbances in this disorder.

Attention fixation training: training people to form cognitive maps help to control symptoms of panic disorder with agoraphobia

Nine individuals diagnosed with panic with agoraphobia received three elements of Attentional Fixation Training (AFT): Directed attention to the external environment, directed topographical synthesis, and directed orientation in space-time to control characteristics of panic. They then walked a standard 2.5 km route and practiced these elements upon entering one of the five panic-inducing situations: (a) walking alone near a busy street with the examiner following at 20 m, (b) walking alone near a busy street with the examiner out of client's visual field, (c) shopping with the examiner present, (d) traveling on a bus alone, and (e) shopping alone. Heart rate was monitored in each of these five situations. Except for the case of using public transport, heart rate activity decreased to a considerable extent during AFT practice suggesting AFT elements provided a good way to control symptoms of panic in vivo. Results were discussed within the confines of a model suggesting that an attentional deficit, which produces a spatial disorientation disorder that maintains both panic and agoraphobia, can efficiently be overcome by means of all three AFT tools.

Nocturnal and daytime panic attacks--comparison of sleep architecture, heart rate variability, and response to sodium lactate challenge

BACKGROUND

The purpose of this study was to determine if nocturnal panic patients have greater autonomic dysregulation than patients with daytime panic.

METHODS

Three groups were studied: patients who suffer from panic attacks during sleep (n = 12), those who suffer from daytime panic attacks only (n = 12), and control subjects (n = 12). Each subject underwent 24-hour holter monitoring for heart rate variability (HRV), an overnight sleep recording, and sodium lactate challenge during wakefulness.

RESULTS

There was a marked subjective response to the sodium lactate challenge in the panic disorder (PD) patients but not in control subjects. Each group showed changes in HRV in response to sodium lactate challenge. The decrease in HRV measures was more marked in PD patients as a whole than in control subjects. During non-rapid eye movement (REM) sleep the value for total power (TP) was significantly higher in the nocturnal panic patients. The PD patients as a whole had higher values for TP and low-frequency (LF) power during REM sleep than control subjects. There were no significant differences between the two PD groups in sleep architecture. The PD patients as a whole had lower sleep efficiency and less stage 4 sleep than control subjects.

CONCLUSIONS

These findings indicate that there are substantial differences between PD and control subjects in autonomic regulation and that there are small differences between patients with daytime panic attacks and those with sleep-related panic attacks.

CCK4-induced panic in healthy subjects I: psychological and cardiovascular effects

Sixteen healthy subjects participated in a crossover, double blind, and placebo-controlled study, designed to assess simultaneously the psychological and cardiovascular effects of cholecystokinin tetrapeptide (CCK4). Following an i.v. injection of 25 microg of CCK4, 44 percent of subjects experienced symptoms that fulfilled the DSM-IV criteria for a panic attack while no one panicked with placebo. CCK4 induced a significantly greater number and higher intensity of panic-like symptoms than placebo. A significant increase in state anxiety was observed in the period after CCK4 injection; this increase was significantly larger than the non-specific anxious reaction to placebo. CCK4 also affected cardiovascular signs. Both heart rate and mean blood pressure significantly increased after administration of CCK4. Again, these increases were significantly higher than those seen after placebo injection. We conclude that, in healthy subjects, CCK4 induces panic-like reaction characterized by a number of somatic, cognitive and emotional symptoms, which are accompanied by increases in heart rate and blood pressure.

Anxiety and cardiovascular reactivity: the basal forebrain cholinergic link

The relations between anxiety states and autonomic functions are considered from the vantage of a model of the neural systems underlying anxiety and autonomic control. An important component of this model is the involvement of the basal forebrain cortical cholinergic system that is seen to play a crucial role in the cognitive aspects of anxiety, and the links between anxiety and autonomic regulation. An additional aspect of the model is the detailing of the routes by which autonomic reactivity and associated visceral afference can modulate more rostral components of the system. The proposed model offers a more comprehensive framework for research on the neurobiology of anxiety and autonomic control.

Why do episodes of panic stop?

Episodes of panic are self-limiting--they all come to an end. However, it has not been explained how and why they end. Neither the cognitive nor the biological theory of panic deals with this phenomenon. As a first step toward an understanding of what stops a panic, we collected evidence about the self-limiting nature of these episodes. A semistructured interview was developed and conducted with 25 participants who had received a diagnosis of panic disorder. Participants reported a variety of triggers of panic, signs that a panic was ending, and strategies used to terminate panic episodes. A substantial proportion of participants indicated that there was a refractory period following panic episodes. The theoretical and therapeutic significance of this self-limiting feature of panic episodes is considered, as is the probable occurrence of a postpanic refractory period.

Anxiety and autonomic flexibility: a cardiovascular approach

Autonomic characteristics of panickers, blood phobics, and nonanxious controls were compared with a variety of cardiovascular measures, including spectral analysis of the cardiac inter-beat interval time series (derived from the electrocardiogram). Responses to laboratory stressors (shock avoidance and cold face stress) of 16 participants who reported recent occurrences of frequent severe panic attacks, 15 participants who reported strong somatic reactions and fainting to the sight of blood, and 15 controls, were recorded. Results suggested distinct autonomic patterns among the three groups. Across conditions, panickers displayed the highest heart rates (HR) coupled with the least HR variability, which indicates low levels of cardiac vagal tone. Blood phobics showed more vagally mediated HR variability than panickers, with a significant association between cardiac rate and mean arterial pressure. Controls generally showed the most HR variability and 'spectral reserve' (a quality that indicates flexible responsivity). Results are discussed in the context of traditional models of anxiety and autonomic activity in contrast to contemporary notions of stability and change in biological systems.

Chest pain, palpitations and panic

Chest pain and palpitations are commonly described in the general population and are frequent presenting symptoms in all medical settings. Although often transient, they can be persistent and are associated with considerable disability, distress, and concern about heart disease and use of medical resources. Both symptoms are associated with panic but also with other psychiatric disorders. It is most useful to consider etiology as multicausal and interactive; psychological factors affect interpretation of bodily perceptions and have deleterious effects on quality of life and use of medical resources. There is evidence that general measures and specific drug and psychological treatments can be effective. There is still uncertainty about the most appropriate ways of providing effective care to large numbers of patients.

The relationship between plasma MHPG and NE: employing regression models in estimating centrally derived MHPG and peripheral NE turnover rate in panic disorder

Studies investigating the role of the noradrenergic system in the pathophysiology of anxiety have focused on measuring plasma 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) levels. Fewer studies have examined norepinephrine levels. Basal plasma norepinephrine and free MHPG levels were simultaneously measured in 33 normal controls and 20 panic disorder (PD) patients. Norepinephrine levels were similar in patients and controls, but MHPG levels were significantly lower in patients (13.34 +/- 3.22 vs 18.37 +/- 4.49 pmol ml-1, p < 0.0001). Norepinephrine correlated significantly with plasma MHPG levels in controls (r = 0.538, p < 0.0001) and patients (r = 0.645, p < 0.002). Patients had a trend toward a lower y-intercept than controls, suggesting a lower contribution by the CNS to MHPG pool plasma levels (9.18 vs 12.51, p < 0.08). Norepinephrine turnover rate was similar in patients and controls. We propose that the dysregulation in the noradrenergic system in PD may be akin to animal studies of acute-on-top-of-chronic stress paradigms, whereby chronic stress results in normal or decreased basal NE turnover and sensitized responses to recurrent stresses.

Autonomic balance revisited: panic anxiety and heart rate variability

The analysis of heart rate variability (HRV) is becoming widely used in clinical research to provide a window into autonomic control of HR. This technique has been valuable in elucidating the autonomic underpinnings of panic disorder (PD), a condition that is marked by reports of heart palpitations. A body of research has emerged that implicates a relative reduction in HRV and cardiac vagal tone in PD, as indicated by various HRV measures. These data are consistent with the cardiac symptoms of panic attacks, as well as with developmental evidence that links high vagal tone with enhanced attention, effective emotion regulation, and organismic responsivity. Implications of these findings for nosology and pathophysiology are discussed. Reports of reduced HRV in PD contrast with portrayals of excess autonomic lability in anxiety. This contradiction is addressed in the context of traditional homeostatic models versus a systems perspective that views physiologic variability as essential to overall stability.

Intrapatient agreement on phenomenology of panic attacks

Panic disorder is common in primary care settings and such a physician is often a patient's initial contact with the health care system. Previous work concerning the homogeneity of panic phenomenology across patients is contradictory. The purpose of this pilot study was to assess the intrapatient homogeneity of panic attacks and to examine associations between measures of homogeneity and physicians' confidence in the diagnosis. Ten patients meeting DSM-III-R criteria for panic disorder completed a diary documenting the symptomatic phenomenology of five consecutive panic attacks. In addition, the physician rated his diagnostic confidence for each patient. Patterns of symptoms and their sequences during panic showed good agreement within patients as did patterns of abatement and of presence of a precipitating event. The physician's diagnostic confidence was inversely related to agreement on symptom severity and variance of duration of an attack. This study suggests intrapatient homogeneity on most measures.

Noradrenergic mechanisms in stress and anxiety: II. Clinical studies

Studies in animals have shown a relationship between alterations in noradrenergic brain system function and behaviors of anxiety and fear. These findings have generated the hypothesis that the symptoms seen in patients with anxiety disorders may be related to alterations in noradrenergic function. A number of clinical studies have tested this hypothesis, utilizing measures of catecholaminergic function such as heart rate and blood pressure, measurement of norepinephrine and its metabolites in urine and plasma and adrenergic receptor binding in platelets, as well as pharmacological challenge to the noradrenergic system. Acute stressors, such as public speaking, have been associated with an increase in heart rate, blood pressure, and norepinephrine and its metabolites in urine and plasma. Findings in patients with panic disorder at baseline related to heart rate, blood pressure, baseline norepinephrine and its metabolites, and platelet adrenergic receptors have been mixed, while the most consistent findings have been blunted growth hormone response to clonidine and increased 3-methoxy-4-hydroxy-phenylethylene-glucol (MHPG) and anxiety following stimulation of the noradrenergic system with yohimbine. Baseline measures of noradrenergic function in patients with posttraumatic stress disorder (PTSD) have also been mixed, while an increased heart, blood pressure and norepinephrine response to traumatic reminders, as well as increased behavioral (as well as different brain metabolic) response to yohimbine, have been found in PTSD. There are fewer studies of noradrenergic function in the other anxiety disorders, and the findings there have not been consistent. These studies provide evidence for increased noradrenergic responsiveness in panic disorder and PTSD, although there does not appear to be an alteration in baseline noradrenergic function in these patients.

Autonomic characteristics of generalized anxiety disorder and worry

Autonomic characteristics of generalized anxiety disorder (GAD) and worry were examined using measures of heart period variability. The cardiorespiratory responses of 34 GAD clients and 32 nonanxious control subjects were recorded during resting baseline, relaxation, and worry periods. Results indicated differences between GAD subjects and controls as well as among baseline, relaxation, and worry periods. GAD clients exhibited shorter cardiac interbeat intervals (IBIs) and lower high frequency spectral power across all task conditions. Relative to baseline and relaxation conditions, worry was associated with (1) shorter IBIs, (2) smaller mean successive differences (MSD) of the cardiac IBIs, and (3) lower high frequency spectral power. These findings suggest that GAD and its cardinal feature (worry), are associated with lower cardiac vagal control. The findings of the present study provide evidence for the utility of further exploration of the role of autonomic nervous system activity in GAD.

How good are patients with panic disorder at perceiving their heartbeats?

Palpitations are among the most common symptoms of panic attacks. The present review addresses the question of whether systematic differences in heartbeat perception exist between patients with panic disorder and control subjects. Paradigms involving the comparison of heartbeat sensations with external signals such as discrimination task have failed to find group differences. Recent improvements in methodology may give clearer results in future studies. The majority of studies using the mental tracking paradigm have shown that panic disorder patients show a better heartbeat perception than controls. Discrepant results are probably related to different instructions and differences in sample characteristics such as the inclusion of patients on medication affecting the cardiovascular system. More accurate heartbeat perception, may, however, be restricted to those patients who show agoraphobic avoidance behavior. It is also conceivable that group differences in the mental tracking paradigm are due to attentional biases or a tendency to interpret weak sensations as heartbeats rather than differences in perceptual sensitivity. More ambulatory studies are needed to test whether the results can be generalized to the patients' natural environment. So far ambulatory studies have established superior heartbeat perception only in the subgroup of panic disorder patients with cardiac neurosis. A 1-year prospective study showed that heartbeat perception as assessed with the mental tracking paradigm predicted maintenance of panic attacks. This supports the clinical significance of the findings. Increased cardiac awareness may increase the probability of anxiety-inducing bodily sensations triggering the vicious cycle of panic. Laboratory and ambulatory monitoring studies showed that panic disorder patients respond with anxiety when they think that their heart rate has accelerated. Increased cardiac awareness may also contribute to the maintenance of the disorder by motivating the patients to avoid situations in which these sensations occur.