Psychophysiology of relaxation-associated panic attacks

Prefrontal and hippocampal theta rhythm show anxiolytic-like changes during periaqueductal-elicited "panic" in rats

Anxiety and panic are both elicited by threat and co-occur clinically. But, at the neural level, anxiety appears to inhibit the generation of panic; and vice versa. Anxiety and panic are thought to engage more anterior (a) and mid-posterior (m) parts of the periaqueductal gray (PAG), respectively. Anxiety also engages the hippocampus and medial prefrontal cortex. Here, we tested if mPAG but not aPAG stimulation would suppress prefrontal and hippocampal theta rhythm as do anxiolytic drugs. Twelve male rats with implanted electrodes were stimulated alternately (30 s interval) in the left PAG or right reticular formation (reticularis pontis oralis [RPO]-as a positive control) with recording in the left prelimbic cortex and left and right hippocampus. PAG stimulation was set to produce freezing and RPO to produce 7-8 Hz theta rhythm before tests lasting 10 min on each of 5 days. mPAG stimulation decreased, and aPAG increased, theta power at all sites during elicited freezing. mPAG, but not aPAG, stimulation decreased prefrontal theta frequency. Stimulation did not substantially change circuit dynamics (pairwise phase consistency and partial directed coherence). Together with previous reports, our data suggest that panic- and anxiety-control systems are mutually inhibitory, and neural separation of anxiety and panic extends down to the aPAG and mPAG, respectively. Our findings are consistent with recent proposals that fear and anxiety are controlled by parallel neural hierarchies extending from PAG to the prefrontal cortex.

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.

Development and Initial Validation of the Relaxation Sensitivity Index

Relaxation sensitivity indexes the fear of relaxation-related events. The purpose of this study was to develop and provide initial validation of a self-report measure of relaxation sensitivity, the Relaxation Sensitivity Index (RSI). Three independent samples of undergraduate students (n=300 unselected, n=349 non-clinical, and n=197 clinical analogs with elevated anxiety/depression symptoms) completed self-report measures to examine the factor structure, reliability, and validity of the RSI. Results of exploratory and confirmatory factor analyses supported a three-factor structure (correlated Physical, Cognitive, and Social Concerns). The RSI demonstrated good internal consistency and construct validity as evidenced by expected correlations with measures of anxiety and depression symptoms. The RSI showed good predictive validity in terms of a history of fearful responding to relaxation. RSI scores were significantly higher in the symptomatic compared to non-clinical sample. Results suggest the RSI is a valid and reliable measure that may be useful in clinical and research settings.

The paradox of relaxation training: Relaxation induced anxiety and mediation effects of negative contrast sensitivity in generalized anxiety disorder and major depressive disorder

BACKGROUND

The Contrast Avoidance Model postulates that individuals with generalized anxiety disorder (GAD) fear a sharp spike in negative emotion, and thus, prefer to worry to maintain their negative affect rather than being in a more euthymic state, such as relaxation. Relaxation induced anxiety (RIA) is a paradoxical phenomenon wherein people experience a spike in their anxiety during relaxation training. Because these phenomena may be related and may also operate among individuals with major depressive disorder (MDD), we attempted to test whether negative contrast sensitivity was a mediator of GAD or MDD in the prediction of RIA.

METHODS

Individuals with GAD (n = 32), MDD (n = 34), and healthy controls (n = 30) were exposed to a negative emotional contrast by engaging with relaxation practice and then watching a negative emotional video. This was followed by the assessment of their negative contrast sensitivity. After this, participants engaged again with relaxation and RIA was measured. We examined mediation effects of negative contrast on the relationship between diagnostic status and RIA.

RESULTS

Negative contrast sensitivity fully mediated GAD and partially mediated MDD in predicting RIA.

CONCLUSIONS

Our findings support the hypotheses that negative contrast sensitivity is the mediator of both GAD and MDD in predicting RIA. This may have implications for assessment and treatment of GAD and MDD.

Mind the Hype: A Critical Evaluation and Prescriptive Agenda for Research on Mindfulness and Meditation

During the past two decades, mindfulness meditation has gone from being a fringe topic of scientific investigation to being an occasional replacement for psychotherapy, tool of corporate well-being, widely implemented educational practice, and "key to building more resilient soldiers." Yet the mindfulness movement and empirical evidence supporting it have not gone without criticism. Misinformation and poor methodology associated with past studies of mindfulness may lead public consumers to be harmed, misled, and disappointed. Addressing such concerns, the present article discusses the difficulties of defining mindfulness, delineates the proper scope of research into mindfulness practices, and explicates crucial methodological issues for interpreting results from investigations of mindfulness. For doing so, the authors draw on their diverse areas of expertise to review the present state of mindfulness research, comprehensively summarizing what we do and do not know, while providing a prescriptive agenda for contemplative science, with a particular focus on assessment, mindfulness training, possible adverse effects, and intersection with brain imaging. Our goals are to inform interested scientists, the news media, and the public, to minimize harm, curb poor research practices, and staunch the flow of misinformation about the benefits, costs, and future prospects of mindfulness meditation.

Psychological Treatments That Cause Harm

The phrase primum non nocere ("first, do no harm") is a well-accepted credo of the medical and mental health professions. Although emerging data indicate that several psychological treatments may produce harm in significant numbers of individuals, psychologists have until recently paid little attention to the problem of hazardous treatments. I critically evaluate and update earlier conclusions regarding deterioration effects in psychotherapy, outline methodological obstacles standing in the way of identifying potentially harmful therapies (PHTs), provide a provisional list of PHTs, discuss the implications of PHTs for clinical science and practice, and delineate fruitful areas for further research on PHTs. A heightened emphasis on PHTs should narrow the scientist-practitioner gap and safeguard mental health consumers against harm. Moreover, the literature on PHTs may provide insight into underlying mechanisms of change that cut across many domains of psychotherapy. The field of psychology should prioritize its efforts toward identifying PHTs and place greater emphasis on potentially dangerous than on empirically supported therapies.

EEG-guided meditation: A personalized approach

The therapeutic potential of meditation for physical and mental well-being is well documented, however the possibility of adverse effects warrants further discussion of the suitability of any particular meditation practice for every given participant. This concern highlights the need for a personalized approach in the meditation practice adjusted for a concrete individual. This can be done by using an objective screening procedure that detects the weak and strong cognitive skills in brain function, thus helping design a tailored meditation training protocol. Quantitative electroencephalogram (qEEG) is a suitable tool that allows identification of individual neurophysiological types. Using qEEG screening can aid developing a meditation training program that maximizes results and minimizes risk of potential negative effects. This brief theoretical-conceptual review provides a discussion of the problem and presents some illustrative results on the usage of qEEG screening for the guidance of mediation personalization.

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.

Dynamics of defensive reactivity in patients with panic disorder and agoraphobia: implications for the etiology of panic disorder

BACKGROUND

The learning perspective of panic disorder distinguishes between acute panic and anxious apprehension as distinct emotional states. Following animal models, these clinical entities reflect different stages of defensive reactivity depending upon the imminence of interoceptive or exteroceptive threat cues. The current study tested this model by investigating the dynamics of defensive reactivity in a large group of patients with panic disorder and agoraphobia (PD/AG).

METHODS

Three hundred forty-five PD/AG patients participated in a standardized behavioral avoidance test (being entrapped in a small, dark chamber for 10 minutes). Defense reactivity was assessed measuring avoidance and escape behavior, self-reports of anxiety and panic symptoms, autonomic arousal (heart rate and skin conductance), and potentiation of the startle reflex before and during exposure of the behavioral avoidance test.

RESULTS

Panic disorder and agoraphobia patients differed substantially in their defensive reactivity. While 31.6% of the patients showed strong anxious apprehension during this task (as indexed by increased reports of anxiety, elevated physiological arousal, and startle potentiation), 20.9% of the patients escaped from the test chamber. Active escape was initiated at the peak of the autonomic surge accompanied by an inhibition of the startle response as predicted by the animal model. These physiological responses resembled the pattern observed during the 34 reported panic attacks.

CONCLUSIONS

We found evidence that defensive reactivity in PD/AG patients is dynamically organized ranging from anxious apprehension to panic with increasing proximity of interoceptive threat. These data support the learning perspective of panic disorder.

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.

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.

Physiologic instability in panic disorder and generalized anxiety disorder

BACKGROUND

Because panic attacks can be accompanied by surges in physiologic activation, we tested the hypothesis that panic disorder is characterized by fluctuations of physiologic variables in the absence of external triggers.

METHODS

Sixteen patients with panic disorder, 15 with generalized anxiety disorder, and 19 normal control subjects were asked to sit quietly for 30 min. Electrodermal, cardiovascular, and respiratory measures were analyzed using complex demodulation to quantify variability in physiologic indices.

RESULTS

Both patient groups reported equally more anxiety and cardiac symptoms than control subjects, but certain other somatic symptoms, including breathlessness, were elevated only in panic disorder patients. Mean end-tidal pCO(2) and respiratory rates were lower, and tidal volume and the number of sighs were higher in panic disorder patients than control subjects. Neither cardiovascular (heart rate, arterial pressure, cardiac output), nor electrodermal instability including sighs distinguished the groups; however, tidal volume instability was greater in panic disorder than generalized anxiety disorder patients or control subjects. Several other respiratory measures (pCO(2), respiratory rate, minute volume, duty cycle) showed greater instability in both patient groups than in control subjects.

CONCLUSIONS

Respiration is particularly unstable in panic disorder, underlining the importance of respiratory physiology in understanding this disorder. Whether our findings represent state or trait characteristics is discussed.

Evoking analogue subtypes of panic attacks in a nonclinical population using carbon dioxide-enriched air

The increasing recognition that panic attacks are heterogeneous phenomena necessitates better and more objective criteria to define and examine what constitutes a panic attack. The central aim of the present study was to classify subtypes of panic attacks (i.e. prototypic, cognitive, and non-fearful) in a nonclinical sample (N = 96) based on the concordance/discordance between subjective and physiological responding to multiple inhalations of 20 and 13% CO2-enriched air. Results show that a substantial proportion of this nonclinical sample (55.2%) responded to the CO2 challenge in a manner consistent with clinical and research definitions of different subtypes of panic attacks. The implications of this dimensional approach for discriminating subtypes of panic in the laboratory are discussed as a means to better understand the phenomenology and nature of panic attacks.

Pulmonary function and dyspnea/suffocation theory of panic

This article presents a brief discussion of pulmonary function and panic attacks in the context of respiratory psychophysiology. Ley's (Behaviour Research and Therapy, 27, 549-554, 1989) earlier dyspnea/suffocation theory of panic is contrasted with Klein's (Archives of General Psychiatry, 50, 306-316, 1993) later false suffocation alarm theory. The distinction between "dyspnea" (the sensation of difficulty in breathing) and "suffocation" (a condition that sometimes gives rise to dyspnea) is emphasized. The brief discussion is followed by a critical comparison of two recent studies on pulmonary function and panic. Asmundson and Stein (Journal of Anxiety Disorders, 8, 63-69, 1994) reported an association between forced expiratory flow rate (a measure of pulmonary function) in panic disorder patients and the severity of panic-related symptoms. They interpreted their findings as support for the dyspnea/suffocation theory of panic since severity of dyspnea is a consequence of pulmonary function. Spinhoven et al. (Behaviour Research and Therapy, 33, 457-460, 1995) failed to replicate the findings of Asmundson and Stein. The present paper provides a critical analysis of the study by Spinhoven et al. and concludes that the failed attempt to replicate may have been a consequence of a flawed methodology (the subjects of the two studies are not comparable on a crucial pulmonary test) and a statistical anomaly (disproportionately small differences between means that exceed predictions based on sampling error). A recommendation is made that future attempts to replicate should pay special care to avoid the possibility of experimenter-demand effects.

Relaxation-induced EEG alterations in panic disorder patients

Based on previous reports of relaxation-induced panic attacks in panic disorder patients, quantitative electroencephalographic (EEG) profiles and subjective anxiety ratings were assessed in panic disorder patients and normal controls listening to neutral and relaxation audiotapes. Regardless of tape condition, patients exhibited a greater frequency and severity of panic-related symptoms. Relaxation failed to alter panic-related symptom ratings or anxiety ratings in patients and controls. Theta and alpha increments were observed during relaxation, but only in normal controls. High frequency beta activity was less evident in patients, regardless of tape conditions. Results are discussed in relation to arousal and treatment issues in panic disorder.

Ironic effects of trying to relax under stress

Two studies found that intentional relaxation under conditions of mental load or stress produces ironic increases in skin conductance level (SCL). In Experiment 1, participants instructed to relax under the high mental load of rehearsing a long number had higher SCL than those instructed to relax under low load, and tended to have higher SCL than those under high load not instructed to relax. In Experiment 2, participants were instructed to relax or were not so instructed while they answered questions described either as measures of IQ or as unimportant. Those in the more loading and stressful situation who were asked to relax had greater SCL during the questions than those not asked to relax.

Dyspneic-fear theory explains hyperventilatory panic attacks: a reply to Carr, Lehrer and Hochron

Carr, Lehrer and Hochron (Behaviour Research and Therapy, 30, 251-261, 1992) attempted to test Ley's (Behaviour Research and Therapy, 30, 549-554, 1989) dyspneic-fear theory and concluded that while their results confirmed predictions for a sample of asthmatics, their results did not confirm predictions for a sample of panic-disorder patients. The present paper points to a basic flaw in the Carr et al. study which renders their conclusions regarding panic disorder indeterminate. The flaw in the Carr et al. study lies in their selection of panic-disorder patients. Whereas dyspneic-fear theory provides an explanation for panic fear experienced in hyperventilatory panic attacks, Carr et al. overlooked this fact and selected Ss based on the DSM-IIIR classification, a set of criteria which does not distinguish between hyperventilatory panic attacks and other types of panic attacks (see Ley, Behaviour Research and Therapy, 30, 347-357, 1992).

Reply to Ley's "dyspneic-fear theory explains hyperventilatory panic attacks"

In a critique of the study by Carr, Lehrer and Hochron (1992), Ley (Behaviour Research and Therapy, 32, 109-111, 1994) attributes the lack of confirmation for his dyspneic-fear theory among panic disorder patients to a basic flaw of that study: Ss were selected according to DSM-IIIR criteria. Ley argues that dyspneic-fear theory pertains exclusively to hyperventilatory (characterized by intense dyspnea) panic attacks not to all attacks that come under the classification of DSM-IIIR. We address the premise concerning the selection of Ss and argue that cognitive theory continues to offer a more convincing explanation of our study and of more recent findings by others.

The many faces of Pan: psychological and physiological differences among three types of panic attacks

The thesis of this paper is that failure to recognize the psychological and physiological differences among panic attacks within DSM-IIIR precludes meaningful comparisons and evaluations of research findings, confounds theoretical issues, and impairs the development of more specific, and thereby more effective, programs of treatment. To remedy this, a recommendation is made to define panic attacks on the basis of psychological and physiological distinctions that fit three categories of severity: Type I (classic panic attack), Type II (anticipatory panic attack), and Type III (cognitive panic attack). The logical-empirical rationale for the categories recommended is presented in the context of relevant research findings. Implications for theory, experimental design, and treatment are discussed.

Ventilatory control of heart rate during inhalation of 5% CO2 and types of panic attacks

Differences in the magnitude of increases in heart rate during prolonged inhalation of 5% CO2 range from a mean of 25 b/min for a group of eight panic-disorder patients who panicked (Woods, Charney, Goodman, & Heninger, 1988. Archives of General Psychiatry, 45, 43-52) to zero b/min for 16 patients, eight of whom panicked (Craske & Barlow, 1990. Journal of Abnormal Psychology, 99, 302-307). What accounts for this disparity? The present paper describes how heart rate can be increased by means of voluntary overbreathing during prolonged inhalation of 5% CO2 in air. This suggests that differences in the degree of overbreathing may explain differences in the magnitude of increases in heart rate during inhalation of 5% CO2. An explanation is also offered for the curious finding that some patients experience "panic attacks" with zero increase in heart rate. Evidence suggests that this is likely to happen in cognitively based panic attacks, in contrast to hyperventilatory attacks or anticipatory attacks.

Affective responses to hyperventilation: a test of the cognitive model of panic

A cognitive explanation of the association between acute hyperventilation and panic attacks has been proposed: the extent to which sensations produced by hyperventilation are interpreted in a negative and catastrophic way is said to be a major determinant of panic. Non-clinical subjects were provided with a negative or a positive interpretation of the sensations produced by equivalent amounts of voluntary hyperventilation. As predicted, there was a significant difference between positive and negative interpretation conditions on ratings of positive and negative affect. Subjects in the positive interpretation condition experienced hyperventilation as pleasant, and subjects in the negative interpretation condition experienced hyperventilation as unpleasant, even though both groups experienced similar bodily sensations and did not differ in their prior expectations of the affective consequences of hyperventilation. When the subjects were given a positive interpretation, the number of their sensations correlated with positive affect; when a negative interpretation was given, the number of bodily sensations correlated with negative affect. The results provide support for a cognitive model of panic and are inconsistent with the view that panic is simply a symptom of hyperventilation syndrome.

Biological correlates of lactate sensitivity in panic disorder

In this pilot study, 9/9 patients with panic disorder experienced a lactate-induced panic attack as compared with 0/9 controls. Baseline measurements were significant for higher anxiety self-ratings, higher heart and respiratory rates, elevated potassium, and lower lymphocyte 3H-dihydroalprenolol (DHA) binding in the patient group. Spielberger State anxiety scores correlated with baseline mean heart rate, and Spielberger Trait anxiety scores with lymphocyte DHA binding. The lactate infusion was not found to differentially affect any physiological or biochemical measures in the two groups, though heart rate surges occurred in most patients. Intravenous propranolol reduced the panic to a negligible degree, whereas intravenous diazepam was quite effective. Neurobiological implications are discussed, and the contradictory biological findings in the lactate literature are reviewed.

Differential reactivity to lactate infusions: the relative role of biological, psychological, and conditioning variables

Nine patients with panic disorder experienced a lactate-induced panic attack, whereas nine controls did not. Higher preinfusion anxiety levels and heart rates were associated with panic disorder, and high baseline anxiety ratings were associated with atypical, severe lactate-induced panic attacks. Nevertheless, it was difficult to reconcile patients' and controls' reactivity to lactate as entirely secondary to baseline differences. Subjects differed qualitatively in the types of specific symptoms experienced and quantitatively in their anxiety and heart rate responses. In most cases, panic began with various central perceptual changes; peripheral cardiovascular and autonomic symptoms followed later. No patient rated a lactate-induced panic attack as identical to a naturally occurring attack. Not only did specific symptoms differ in their severity and order of production, but lactate-induced panic lacked the typical fears of dying, going crazy, or losing control. The results suggest that though environmental effects, expectancy biases, and baseline psychological states play salient roles in modifying the experience of a lactate-induced panic attack, they do not fully account for lactate sensitivity. The relative role that biological, psychological, and conditioning factors play in lactate-induced panic is discussed.

Is panic a unique emotional experience?

The establishment of Panic Disorder (PD) as a distinct diagnostic category stems largely from the conceptualization of panic as a phenomenon qualitatively different from severe levels of anxiety. The current study utilized patients with Generalized Anxiety Disorder (GAD) and Obsessive Compulsive Disorder (OCD) as comparison groups to examine the validity of this conceptualization. Seventeen PD, 29 OCD, and 12 GAD patients completed self-report inventories from which a panic factor was derived. Controlling for level of overall anxiety, the total panic factor was rated significantly higher by the PD group. A cluster of symptoms emerged which differentiated the PD group from the other two groups. The panic items and total score were correlated with total levels of state and trait anxiety but correlations were generally low, accounting for a limited amount of the total variance. Results were interpreted as providing only equivocal support for viewing panic as a separate dimension apart from high levels of general anxiety. A discussion of conceptual issues is presented.

Panic attacks during relaxation and relaxation-induced anxiety: a hyperventilation interpretation

This paper explains how a hyperventilation theory of panic disorder accounts for panic attacks during relaxation and relaxation-induced anxiety. The explanation is based on the observation that chronic hyperventilators maintain a steady state of low pCO2 (arterial carbon dioxide tension) and are, therefore, sensitive to relatively small increases in ventilation when metabolism is low and to relatively sudden reductions in metabolism when ventilation is relatively constant. Thus, if minute volume of air breathed remains constant while the metabolic production of CO2 decreases, as in the case of one who sits down or lies down to relax, respiratory hypocapnea may increase in intensity until it produces the familiar sensations which mark the panic attack. Data from relevant studies of panic attacks during relaxation support the hyperventilation interpretation.

Treadmill exercise test and ambulatory measures in panic attacks

Treadmill exercise test performance and ambulatory heart rate and activity patterns of 40 patients with panic attacks were compared with 20 age-matched controls (control group 1) and 20 nonexercising controls (control group 2). All patients underwent a symptom-limited exercise stress test. Panic attack patients and control group 1 wore an ambulatory heart rate/activity monitor for up to 3 days. Panic patients had a significantly higher heart rate at 4 and 6 METS than either control group. The max METS were 11.2 +/- 2.3, 13.5 +/- 2.3 and 11.2 +/- 1.8 for the panic attack patients and control groups 1 and 2, respectively. One panic patient had ischemia on the treadmill at 12 METS. Panic patients had a significantly higher standing heart rate than controls. Furthermore, 11 of 39 panic patients had tachycardia on standing compared with 3 of 40 controls. Panic attack patients had higher wake and sleep heart rates than control group 1, but the differences were not significant. These results are consistent with autonomic dysfunction in panic patients but may also be due to differences in physical conditioning. The treadmill can be useful for reassuring patients and for identifying the rare patient with ischemia on exercise.

Panic disorder and agoraphobia: fear of fear or fear of the symptoms produced by hyperventilation?

Two versions of the fear-of-fear hypothesis of panic disorder are discussed. The fear-of-the-somatic-effects-of-fear version, which is distinguished from the classical conditioning version, is compared with the hyperventilation theory of panic disorder and agoraphobia. The fear-of-the-somatic-effects-of-fear hypothesis is criticized on the basis of its inability to explain adequately (a) the initiation of panic attacks, (b) the growth in intensity of panic attacks, and (c) the termination of panic attacks. The tenability of the hyperventilation theory is supported by evidence from programs of treatment derived from the basic assumptions of the theory.

Skin conductance feedback and panic attacks

A method is described for using skin conductance response (SCR) biofeedback to help patients control their panic attacks. The SCR signal is presented as a symptom analogue, and patients practice provoking and subduing the signal, using a combination of cognitive strategies and physiological relaxation.

Lactate infusions and panic attacks: do patients and controls respond differently?

Ten patients with panic disorder or agoraphobia with panic attacks and 10 normal controls received infusions of normal saline (placebo) and sodium lactate in a single-blind design. The time course of changes in the dependent variables was closely monitored, and expectancy biases and demand characteristics were minimized. Lactate increased self-reported anxiety and heart rate equally in patients and controls. The only variables showing statistically different responses between the groups were systolic and diastolic blood pressure. Overall, in both groups, the effects of lactate were quite similar to states of natural panic or anxiety for both self-report measures and heart rate. Patients had a tendency to endorse somatic symptoms indiscriminately. Our data do not support response to lactate as a biological marker of proneness to panic attacks.