Relationships between the anxiety sensitivity index, the suffocation fear scale, and responses to CO2 inhalation

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

BACKGROUND/RATIONALE

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

METHOD

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

RESULTS

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

DISCUSSION

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

When dyspnea gets worse: Suffocation fear and the dynamics of defensive respiratory responses to increasing interoceptive threat

In patients with anxiety and/or respiratory diseases, body sensations, particularly from the respiratory system, may increase in intensity and aversiveness and thus lead into defensive action (e.g., escape) or panic. The processes, however, that might contribute to the culmination of symptoms and the switch into defensive action have not been well understood yet. The current study aimed at evaluating an experimental paradigm to characterize the dynamics of defensive mobilization to body sensations increasing in intensity and aversiveness. Persons reporting low and high suffocation fear (SF; N = 69) were exposed to increasingly unpleasant feelings of dyspnea induced by inspiratory resistive loads and a breathing occlusion requiring voluntary breath holding. Respiratory responses were assessed along with subjective reports of anxiety and panic symptoms. Presentation of respiratory loads with increasing physical resistance led to increasingly unpleasant feelings of dyspnea. Twenty-eight participants terminated the exposure prematurely at least once. When dyspnea was severe, high compared to low SF persons exhibited an increased respiratory rate that was accompanied by reports of more intense panic symptoms. Premature terminations of exposure were preceded by a surge in anxiety, breathing frequency, and mouth pressure, and a decrease in tidal volume. We successfully established an experimental paradigm to assess changes in defensive responding with increasing intensity of an interoceptive threat. The current data foster our understanding of behavioral expression patterns observed in patients with anxiety and/or respiratory diseases and the processes involved in the culmination of bodily sensations and anxiety into panic.

The benefits of being mindful: trait mindfulness predicts less stress reactivity to suppression

BACKGROUND AND OBJECTIVES

There has been a recent proliferation of research evaluating the efficacy of mindfulness as a clinical intervention. However, there is still little known about trait mindfulness, or how trait mindfulness interacts with maladaptive emotion regulation strategies. The current study further explores the effect of trait mindfulness on emotion regulation, as well as whether specific factors of trait mindfulness are uniquely associated with subjective and autonomic reactivity to stress.

METHODS

Forty-eight healthy male participants were trained in the use of the suppression strategy and then instructed to suppress their responses to the inhalation of a 15% CO2-enriched air mixture for 90 s while their subjective distress and heart rate were recorded.

RESULTS

After controlling for anxiety-related variables, the ability to provide descriptions of observed experiences predicted less heart rate reactivity to CO2 inhalation, while skillfulness at restricting attention to the present moment was uniquely predictive of less subjective distress. The tendency to attend to bodily or sensory stimuli predicted greater distress during CO2 inhalation.

LIMITATIONS

The inclusion of only healthy males limits the generalizability of study findings. Also, the sample size was relatively small.

CONCLUSIONS

These findings suggest that factors associated with trait mindfulness predict less stress reactivity and distress while engaging in suppression above and beyond other variables that have been shown to predict anxious responding. The implications for emotion and clinical research are discussed.

The role of "interoceptive" fear conditioning in the development of panic disorder

More than 20% of the general population experience a panic attack at least once in their lives; however, only a minority goes on to develop panic disorder (PD). Conditioning mechanisms have been proposed to explain this evolution in persons who are susceptible to developing panic disorder upon a "traumatic" panic attack. According to preparedness theory, some cues are more likely to condition than others, namely, those referring to internal, bodily signals of danger. The aim of the present study was to test this theory in a differential conditioning paradigm, making use of scripts referring to different internal, bodily sensations as conditioned stimulus (CS) and inhalation of 35% CO(2) as unconditioned stimulus (UCS). Thirty-three healthy volunteers were assigned to three scripts conditions: "suffocation," "neutral," or "urgency." During acquisition, one of two versions of a particular script was always followed by an inhalation of 35% CO(2) (CS+) and the other by room air (CS-). Acquisition was followed by a test phase, where only inhalations of room air were administered. In line with our hypothesis, only participants in the suffocation condition exhibited a selective conditioning effect. They were more fearful and showed a significantly higher increase in tidal volume than participants in the two control conditions. Results are discussed with relation to interoceptive conditioning, preparedness, and the possible role of tidal volume in PD.

Acute panicogenic, anxiogenic and dissociative effects of carbon dioxide inhalation in patients with post-traumatic stress disorder (PTSD)

BACKGROUND

Increased anxiety and panic to inhalation of carbon dioxide (CO(2)) has been described in patients with anxiety disorders, especially panic disorder, compared to healthy subjects. Post-traumatic stress disorder (PTSD) has been hypothesised to resemble panic disorder and is currently classified as an anxiety disorder in DSM-IV. However, there are only very few data available about the sensitivity of patients with PTSD to CO(2).

METHODS

In 10 patients with PTSD, 10 sex- and age-matched healthy subjects and 8 patients with panic disorder we assessed anxiety, panic, dissociative and PTSD symptoms before and after a single vital capacity inhalation of 35% CO(2).

RESULTS

Patients with PTSD showed an increased anxiety, panic and dissociative reaction to the inhalation of 35% CO(2) compared to healthy participants. PTSD subjects' responses were indistinguishable from those of panic patients. Additionally, PTSD-typical symptoms like post-traumatic flashbacks were provoked in patients with PTSD after the inhalation of CO(2).

CONCLUSIONS

In our sample, PTSD was associated with an increased CO(2) reactivity, pointing to an increased susceptibility of PTSD patients to CO(2) challenge.

The Dutch Claustrophobia Questionnaire: psychometric properties and predictive validity

Fear of suffocation and fear of restriction are thought to underlie claustrophobia and can be assessed with the Claustrophobia Questionnaire (CLQ; Radomsky et al., 2001). A first study tested the psychometric properties of a Dutch version of the CLQ. Students (N=363) completed a Dutch translation of the CLQ and a set of other questionnaires assessing other specific fears, anxiety or depression. Results confirmed the two-factor structure and showed that the Dutch version of the CLQ has good psychometric properties. A second study tested the predictive validity of the Dutch CLQ. Participants (N=23) were exposed each to nine claustrophobic situations with elements of suffocation, restriction or both. The Dutch CLQ was found to be a significant predictor of fear and respiratory reactivity during claustrophobic exposure. It can be concluded that the Dutch version of the CLQ is a reliable and valid instrument to assess claustrophobic fear.

The impact of panic disorder on interoception and dyspnea reports in chronic obstructive pulmonary disease

The prevalence of panic disorder (PD) in patients with chronic obstructive pulmonary disease (COPD) is significantly higher than that in the general population. Comorbid anxiety disorders in COPD are associated with a number of worse outcomes, however little is known about the mechanisms by which PD affects patients with COPD. We hypothesized that patients with COPD and PD would have greater dyspnea severity, but not greater somatosensory sensitivity, to dyspneic stimuli. We studied 10 patients with COPD and PD, 9 patients with COPD without PD, and 9 healthy, matched controls. Participants were administered the Anxiety Sensitivity Index-3. We tested interoceptive sensitivity using a respiratory load detection protocol and dyspnea ratings in response to inspiratory resistive loads. Participants with COPD and PD had higher anxiety sensitivity scores and reported greater dyspnea in response to resistive loads. However no group differences were found in resistive load detection threshold. Anxiety sensitivity scores accounted for a significant amount of the variance in the group difference in dyspnea ratings. Patients with COPD and PD do not show heightened interoceptive sensitivity, but report greater dyspnea to inspiratory resistive loads. Emotional responses to dyspneic sensations may account for higher dyspnea ratings in patients with PD and COPD.

Überprüfung der psychometrischen Qualität der deutschen Version des Angstsensitivitätsindex-3

Zusammenfassung. Angstsensitivität ist ein Konstrukt, das bei der Ätiologie von Angststörungen relevant ist und sich in der internationalen Forschung zunehmender Beliebtheit erfreut. Bisher existiert jedoch kein aktuelles deutschsprachiges Instrument mit einer robusten faktoriellen Validität zur Erfassung von Angstsensitivität. Daher zielte diese Studie darauf ab, die psychometrische Qualität einer deutschsprachigen Version des Anxiety Sensitivity Index-3 ( Taylor et al., 2007 ) zu überprüfen. In die Auswertung gingen Daten von insgesamt N = 5477 Personen aus drei Ländern ein. Die Ergebnisse belegen eine zufriedenstellende Messgenauigkeit, faktorielle Validität und Konstruktvalidität der Übersetzung. Zudem konnte die Messinvarianz mit der englischsprachigen Originalversion gezeigt werden. Die praktischen und theoretischen Implikationen der Ergebnisse werden diskutiert.

Anxiety sensitivity as an incremental predictor of later anxiety symptoms and syndromes

Although anxiety sensitivity (AS) has been shown to predict anxiety symptoms and panic, this literature is limited in regard to evaluating AS as an incremental predictor of anxiety psychopathology relative to other established risk factors including sex and negative affect. The present report prospectively evaluated whether AS was predictive of later changes in anxiety symptoms after controlling for potential confounding factors. Consistent with hypothesis, AS was found to be a significant, incremental predictor of anxiety symptoms over time, even after controlling for sex and negative affectivity. These data provide novel evidence for the unique association between AS of the development of anxiety symptoms.

Panic disorder subtypes: further clinical differences

Panic disorder (PD) is a heterogeneous phenomenon with respect to symptom profile. Most studies agree that a group of patients with prominent respiratory symptoms emerged as a distinct PD subtype. In this study we compared a range of clinical features associated with PD and agoraphobia in patients with respiratory (RS) and nonrespiratory (NRS) subtypes of PD. The participants were 124 patients with PD (79 women and 45 men), with or without agoraphobia, diagnosed by DSM-IV criteria. Following the observer-rated Panic Disorder Severity Scale assessment, subjects completed self-report measures, including the Anxiety Sensitivity Index (ASI), Panic-Agoraphobia Scale; the Beck Anxiety Inventory; and the Panic-Agoraphobic Spectrum Scale (PAS-SR). Multivariate analysis of variance (MANOVA) showed significant group differences [Pillai's trace = 0.95, F (5, 118)(=)2.48, P = .036]. Patients in RS group had higher mean total scores on the ASI (F = 5.00, df = 1, P = .027) and PAS-SR (F = 11.23, df = 1, P = .001) than patients in NRS group. Also, patients with RS attained higher scores than patients with NRS on four domains of PAS-SR (panic-like symptoms, agoraphobia, separation sensitivity, and reassurance seeking). A descriptive discriminant analysis of the data correctly identified 69.4% of the patient group in general and 86.1% of RS group (Wilks's lambda = 0.87, df = 8, P = .048). The significant discriminating factors of the RS and NRS groups were domains of panic-like symptoms, agoraphobia, separation sensitivity, and reassurance seeking. Our findings suggest that anxiety sensitivity and panic-agoraphobic spectrum symptoms might be particularly relevant to understanding subtypes of PD.

Anxiety sensitivity as a predictor of panic attacks

Anxiety sensitivity (AS) is the fear of physical symptoms of anxiety and related sensations believed to have harmful consequences. AS may play a central role in the nature and etiology of panic disorder (PD) and the genesis of panic attacks. We collected Anxiety Sensitivity Index (ASI) scores from PD patients and controls to determine if AS accurately predicts panic. ASIs were completed prior to panic induction using the modified Read rebreathing test in both hypoxic and hyperoxic conditions. Total scores first-order factors, and individual item ASI scores were correlated with panic presence (Spearman correlation) for each of the hypoxic and hyperoxic rebreathing tests for both study populations. Control subjects' data correlated significantly for items 4, 8, and 11 of the ASI for the hyperoxic (n=9; r(S)=0.63, 0.70, and 0.63, respectively) and items 4 and 8 for the hypoxic rebreathing tests (n = 9; r(S) = 0.63 and 0.70, respectively). Panic patients' data correlated significantly for item 1 of the ASI for hyperoxic tests (n=8; r(S)=0.76) and item 5 for the hypoxic tests (n = 8; r(S) = 0.95). Total ASI scores or first-order factors (physical, social concerns, and mental incapacitation) scores of either study group did not correlate significantly with panic presence. AS may not be a reliable predictor of panicogenic responses to CO2-induced panic in either PD or normal control populations. AS may not be an ultimate causal element in eliciting panic attacks.

Cross cultural evaluation of smokers risk for panic and anxiety pathology: a test in a Russian epidemiological sample

The present study evaluated the main and interactive effects of level of smoking (cigarettes per day) and anxiety sensitivity (fear of anxiety and anxiety related sensations) in predicting panic and anxiety variables in an epidemiologically-defined sample of smokers from Moscow (n=95). The combination of high levels of anxiety sensitivity and smoking predicted agoraphobic avoidance, but not frequency of panic attacks during the past week. These findings suggest anxiety sensitivity may moderate the relation between level of smoking and prototypical panic psychopathology variables (panic attacks and agoraphobic avoidance) even after controlling for the theoretically-relevant factors of alcohol abuse and negative affect.

Anxiety sensitivity in first-degree relatives of patients with panic disorder

Anxiety sensitivity (AS) has been proposed as a risk factor for the development of panic disorder. Strong familial-genetic influences in panic disorder (PD) have been reported. AS may be familial too. The current study therefore examined whether first-degree relatives of PD patients are more anxiety-sensitive than normals. Twenty-three first-degree relatives of PD patients, 38 PD patients and 30 normals were given the Anxiety Sensitive Index and the Body Sensations Questionnaire. It was found that the first-degree relatives were, indeed, more anxiety-sensitive than the normals, but less so than the PD patients, suggesting that AS runs in families.

Anxiety sensitivity and 35% CO2 reactivity in patients with panic disorder

OBJECTIVE

The present study examines the possible relationships between anxiety sensitivity (AS) and reactivity to the 35% carbon dioxide (CO(2)) challenge in panic disorder (PD).

METHODS

One-hundred eight patients with PD underwent the 35% CO(2) challenge and completed the Anxiety Sensitivity Index (ASI). Multiple regression analyses were applied to evaluate the role of AS as a predictor of CO(2)-induced anxiety.

RESULTS

Fifty-six patients with PD showed high AS scores, whereas 48 showed medium scores and 4 low scores. ASI scores significantly predicted symptomatological reaction to CO(2) but not subjective induced anxiety.

CONCLUSION

These findings suggest that the fear of anxiety-related bodily sensations was related to the symptomatological reactivity to CO(2) but did not seem to play a crucial role in the modulation of the subjective anxiogenic/panicogenic response to hypercapnia in patients with PD.

Anxiety sensitivity and panic disorder

Anxiety sensitivity refers to fears of anxiety-related sensations. Most often measured by the Anxiety Sensitivity Index (ASI), anxiety sensitivity is a dispositional variable especially elevated in people with panic disorder. Regardless of diagnosis, ASI scores often predict panic symptoms in response to biological challenges (e.g., carbon dioxide inhalation) that provoke feared bodily sensations. Prospective longitudinal studies indicate that scores on the ASI predict subsequent spontaneous attacks, indicating that elevated anxiety sensitivity is a risk factor for panic and perhaps panic disorder. Cognitive behavioral treatment reduces anxiety sensitivity in panic patients, perhaps protecting against relapse. Imipramine likewise decreases anxiety sensitivity.