Social anxiety symptoms uniquely predict fear responding to 35% CO(2) challenge

Physiological correlates of anxiety in childhood and adolescence: A systematic review and meta-analysis

Anxiety is one of the most prevalent problems that affects children and adolescents. The vast majority of diagnostic tools for anxiety depend on written or verbal reports from children and adolescents or their significant others. The validity and reliability of such reports can be compromised by their subjective nature. Thus, there is growing interest in whether anxiety can be indexed with objective physiological measures. The key aim of this systematic review and meta-analysis was to determine which physiological measures are most reliably associated with elevated levels of anxiety amongst children and adolescents. Online databases (e.g., PsycINFO, Embase, Medline) were searched for relevant studies according to pre-determined criteria. Twenty-five studies comprising 2502 participants (N = 1160 with high anxiety) met inclusion, identifying 11 groups of physiological measures. Our meta-analysis revealed that skin conductance level is the most sensitive measure of anxiety (d = 0.83), followed by electromyography (EMG) measures (d = 0.71) and skin conductance response (d = 0.58). However, the included studies varied in terms of subjective measures, study designs, experimental task measures, and physiological measures. Consideration of these differences in methodology offer potential directions for future research.

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

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

Psychometric properties of an innovative self-report measure: The Social Anxiety Questionnaire for adults

This article presents the psychometric properties of a new measure of social anxiety, the Social Anxiety Questionnaire for adults (SAQ), composed of 30 items that were developed based on participants from 16 Latin American countries, Spain, and Portugal. Two groups of participants were included in the study: a nonclinical group involving 18,133 persons and a clinical group comprising 334 patients with a diagnosis of social anxiety disorder (social phobia). Exploratory and confirmatory factor analyses supported a 5-factor structure of the questionnaire. The factors were labeled as follows: (1) Interactions with strangers, (2) Speaking in public/talking with people in authority, (3) Interactions with the opposite sex, (4) Criticism and embarrassment, and (5) Assertive expression of annoyance, disgust, or displeasure. Psychometric evidence supported the internal consistency, convergent validity, and measurement invariance of the SAQ. To facilitate clinical applications, a receiver operating characteristics (ROC) analysis identified cut scores for men and women for each factor and for the global score.

Reactivity to 35% carbon dioxide in bulimia nervosa and panic disorder

The inhalation of 35% carbon dioxide (CO₂) induces panic and anxiety in people with panic disorder (PD) and in people with various other psychiatric disorders. The anxiogenic effect of CO₂ in people with eating disorders has received sparse attention despite the fact that PD and bulimia nervosa (BN) have several common psychological and neurobiological features. This study compared CO₂-reactivity across three groups of participants: females with BN, females with PD, and female controls without known risk factors for enhanced CO₂-reactivity (e.g., social anxiety disorder, first degree relatives with PD). Reactivity was measured by self-reported ratings of panic symptomatology and subjective anxiety, analyzed as both continuous variables (change from room-air to CO₂) and dichotomous variables (positive versus negative responses to CO₂). Analyses of each outcome measure demonstrated that CO₂-reactivity was similar across the BN and PD groups, and reactivity within each of these two groups was significantly stronger than that in the control group. This is the first study to demonstrate CO₂-hyperreactivity in individuals with BN, supporting the hypothesis that reactivity to this biological paradigm is not specific to PD. Further research would benefit from examining transdiagnostic mechanisms in CO₂-hyperreactivity, such as anxiety sensitivity, which may account for this study's results.

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.

Fear responding to 35% CO(2) challenge as a vulnerability marker for later social anxiety symptoms

The majority of biological challenge studies have focused on panic disorder though there is a small literature suggesting that patients with social anxiety disorder (SAD) show comparable responding. These cross-sectional studies suggest that CO(2) reactivity may be a marker of vulnerability to social anxiety. However, the nature of this association is unclear due to design limitations in this literature. The present report prospectively evaluated whether response to a 20% CO(2) challenge was predictive of later changes in social anxiety symptoms. A large non-clinical sample of young adults (N=404) screened for axis I disorders completed a 20% CO(2) challenge and were followed for approximately 18 months. Consistent with the vulnerability hypothesis, those showing greater reactivity to the CO(2) challenge showed increased social anxiety symptoms over time. This significant association was maintained after controlling for gender and trait anxiety. These data provide novel evidence suggesting that CO(2) sensitivity is predictive of the development of social anxiety symptoms.