Reactivity to challenge with carbon dioxide as a prospective predictor of panic attacks

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.

Examination of a brief computerized Cognitive Anxiety Sensitivity intervention on obsessive-compulsive symptoms

OBJECTIVES

Despite the existence of several first-line treatments for obsessive-compulsive disorder (OCD), many patients fail to experience symptom reduction and/or do not complete treatment. As a result, the field has increasingly moved towards identifying and treating malleable underlying risk factors that may in turn improve treatment efficacy. One salient underlying risk factor, anxiety sensitivity (AS) cognitive concerns, has been found to be uniquely associated with obsessive-compulsive (OC) symptom dimensions. However, no studies have yet examined whether reductions in AS cognitive concerns will lead to subsequent reductions in OC symptoms.

METHODS

The current study attempted to fill this gap by recruiting individuals reporting elevations on both AS cognitive concerns and at least one OC symptom dimension. Participants were randomly assigned to receive either a one-session AS cognitive concerns intervention (n = 35) or a single health information control session (n = 37). AS cognitive concerns were assessed at post-intervention and one-month follow-up.

RESULTS

The active intervention produced significantly greater reductions in AS cognitive concerns post-intervention than the control intervention. However, this effect was no longer significant at one-month follow-up. Further, while there was not an effect of treatment condition on OC symptoms at one-month follow-up, changes in AS cognitive concerns from baseline to post-intervention mediated changes in OC symptoms at one-month follow-up.

CONCLUSIONS

Findings support previous research attesting to the malleable nature of AS. Extending this research, findings provide initial support for the efficacy of AS interventions among individuals with elevated OC symptoms.

PRACTITIONER POINTS

Clinicians should consider assessing anxiety sensitivity (AS) among patients with obsessive-compulsive disorder. If elevated, clinicians should consider targeting AS as an adjunct to treatment as usual.

Impact of ovariectomy and CO2 inhalation on microglia morphology in select brainstem and hypothalamic areas regulating breathing in female rats

The neural network that regulates breathing shows a significant sexual dimorphism. Ovarian hormones contribute to this distinction as, in rats, ovariectomy reduces the ventilatory response to CO2. Microglia are neuroimmune cells that are sensitive to neuroendocrine changes in their environment. When reacting to challenging conditions, these cells show changes in their morphology that reflect an augmented capacity for producing pro- and anti-inflammatory cytokines. Based on evidence suggesting that microglia contribute to sex-based differences in reflexive responses to hypercapnia, we hypothesized that ovariectomy and hypercapnia promote microglial reactivity in selected brain areas that regulate breathing. We used ionized calcium-binding-adapter molecule-1 (Iba1) immunolabeling to compare the density and morphology of microglia in the locus coeruleus (LC), the caudal medullary raphe, the caudal part of the nucleus of the tractus solitarius (cNTS), and the paraventricular nucleus of the hypothalamus (PVN). Tissue was obtained from SHAM (metaestrus) female rats or following ovariectomy. Rats were exposed to normocapnia or hypercapnia (5% CO2, 20 min). Ovariectomy and hypercapnia did not affect microglial density in any of the structures studied. Ovariectomy promoted a reactive phenotype in the cNTS and LC, as indicated by a larger morphological index. In these structures, hypercapnia had a relatively modest opposing effect; the medullary raphe or the PVN were not affected. We conclude that ovarian hormones attenuate microglial reactivity in CO2/H+ sensing structures. These data suggest that microglia may contribute to neurological diseases in which anomalies of respiratory control are associated with cyclic fluctuations of ovarian hormones or menopause.

Parental Presence Impacts a Neural Correlate of Anxiety (the Late Positive Potential) in 5-7 Year Old Children: Interactions with Parental Sensitivity to Child Anxiety

Anxiety disorders tend to onset early in development and often result in chronic impairment across the lifespan. Thus, there is substantial interest in identifying early neural markers of anxiety and leveraging these markers to better understand processes leading to anxiety. The late positive potential (i.e., LPP) indexes sustained attention to motivationally relevant stimuli; and the LPP to negative images is increased in individuals with anxiety. In the current study, we examined how parental presence impacts the LPP to threatening images in children (52.6% male) between 5 and 7 years-old (N = 78). Moreover, we explored interactions with parental sensitivity to child anxiety symptoms. Results suggest that when children are in the presence of their parent (compared to the presence of an experimenter), they displayed a larger LPP to threatening images. LPP activity was modulated by parental response to their child's anxiety symptoms, such that children with parents who were overly reactive to their children's anxiety symptoms had the greatest LPP response when viewing threatening stimuli in their parent's presence. Additionally, exploratory analyses indicated that children with clinical and subclinical anxiety were characterized by an increased LPP to negative images, but only when the LPP was measured with parents in the room. Findings are novel and extend previous work by suggesting that parents who react strongly when observing their children's anxiety symptoms in turn increase their child's engagement with threatening stimuli, thereby placing them at greater risk for anxiety.

Assessing vulnerability to panic: a systematic review of psychological and physiological responses to biological challenges as prospective predictors of panic attacks and panic disorder

Background

Cognitive–behavioural theories of panic disorder posit that panic attacks arise from a positive feedback loop between arousal-related bodily sensations and perceived threat. In a recently developed computational model formalising these theories of panic attacks, it was observed that the response to a simulated perturbation to arousal provided a strong indicator of vulnerability to panic attacks and panic disorder. In this review, we evaluate whether this observation is borne out in the empirical literature that has examined responses to biological challenge (eg, CO₂ inhalation) and their relation to subsequent panic attacks and panic disorder.

Method

We searched PubMed, Web of Science and PsycINFO using keywords denoting provocation agents (eg, sodium lactate) and procedures (eg, infusion) combined with keywords relevant to panic disorder (eg, panic). Articles were eligible if they used response to a biological challenge paradigm to prospectively predict panic attacks or panic disorder.

Results

We identified four eligible studies. Pooled effect sizes suggest that there is biological challenge response has a moderate prospective association with subsequent panic attacks, but no prospective relationship with panic disorder.

Conclusions

These findings provide support for the prediction derived from cognitive–behavioural theories and some preliminary evidence that response to a biological challenge may have clinical utility as a marker of vulnerability to panic attacks pending further research and development.

Trial registration number

135908.

Cortisol, Testosterone, and Prospective Risk for War-zone Stress-Evoked Depression

Introduction

The major challenges of efforts to reveal biological risk factors and biomarkers of depression include the complexity of underlying systems, interactions with other systems, and contextual factors governing their expression. Altered endocrine function is believed to be a central contributor to depressive illness, but across studies, evidence for a link between endocrine markers and depression has been mixed, inconclusive, or conditional in nature. In the present study, we evaluated basal testosterone (T), cortisol (C), and CO2 inhalation-stress-reactivity measures of these hormones (TR, CR) as pre-deployment moderators of the later impact of war-zone stressors on depression symptoms in-theater.

Materials and Methods

At pre-deployment, U.S. soldiers (N = 120) completed demographic, clinical and hormone measures, and during deployment, they completed monthly, web-based assessments of war-zone stressors and depression symptoms (N = 533 observations). Mixed effects models estimated the effects of the pre-deployment hormone profiles in moderating war-zone stressors' impact on in-theater depression. Models also tested whether hormonally linked risk for later stress-evoked depression depends on pre-existing depression.

Results

Controlling for pre-deployment depression, high T was protective; whereas TR had depressogenic effects that were amplified by pre-deployment depression. Further, high C was protective, but heightened CR was depressogenic, but only among those with elevated pre-deployment depression.

Conclusions

Findings highlight the importance of examining basal and reactivity measures of endocrine function, and use of prospective, longitudinal models to test hypothesized causal pathways associated with depression vulnerability in the war-zone. Results also suggest that pre-existing depression and cortisol may work in tandem to increase vulnerability for later stress-evoked depression in the war-zone.

The Parent Sensitivity to Child Anxiety Index

Anxiety sensitivity (AS) is the perception that anxiety symptoms and experiences have negative consequences, and has been identified as a risk factor for the development of anxiety disorders. AS has been measured in adults and in children, but to date, the construct of parent's sensitivity to their children's anxiety symptoms has not been identified, measured, or evaluated. The current study presents a novel measure of this construct, the Parent Sensitivity to Child Anxiety Index (PSCAI), and an initial evaluation of its psychometric properties. Factor analysis revealed a three-factor structure consisting of parents' concern for physical symptoms, concern of social evaluation, and fear of anxiety symptoms. The PSCAI demonstrated good internal consistency, and was positively correlated with relevant parental constructs such as parental accommodation, anxiety sensitivity, and trait anxiety. This new measurement system opens new avenues for researching the early development of anxiety disorders and the possibility for novel targeted interventions.

Clinical Correlates of Carbon Dioxide Hypersensitivity in Children

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Fear reactivity to cognitive dyscontrol via novel head-mounted display perceptual illusion exercises

BACKGROUND

Anxiety sensitivity cognitive concerns (ASCC), refer to fears of mental catastrophe or losing control over mental processes. Recent findings show that ASCC are related to suicide risk, mood disorders and trauma-related disorders. Using controlled experimental psychopathology paradigms could be one heretofore unutilized method of increasing understanding of ASCC. Our goal was to test fear reactivity to four head-mounted display perceptual illusion challenges designed to bring on feelings of cognitive dyscontrol (i.e., derealization, depersonalization) in a group of high and low anxiety sensitivity cognitive concerns participants.

METHODS

Participants (N=49) with Anxiety Sensitivity Index-3 cognitive scores at least 1.5 SD above or below the mean completed four cognitive dyscontrol challenges utilizing head-mounted display technology.

RESULTS

Results showed all four challenges successfully elicited high cognitive anxiety symptoms. Consistent with other laboratory challenge studies; high versus low ASCC participants reported comparable cognitive symptoms but reported significantly greater fear.

LIMITATIONS

This was an initial proof of concept study designed to examine fear reactivity to cognitive dyscontrol challenges. Therefore, no control exercises were evaluated.

CONCLUSIONS

The finding that fear reactivity to the laboratory challenges can potentially serve as a viable behavioral correlate of ASCC provides a potentially useful exposure exercise for clients experiencing high levels of ASCC. Given the association between ASCC and severe psychopathology, with further investigation and refinement, such exposure exercises could be integrated into cognitive-behavioral treatments.

The role of anxiety sensitivity cognitive concerns in suicidal ideation: A test of the Depression-Distress Amplification Model in clinical outpatients

Suicide constitutes a significant public health burden as global suicide rates continue to increase. Thus, it is crucial to identify malleable suicide risk factors to develop prevention protocols. Anxiety sensitivity, or a fear of anxiety-related sensations, is a potential malleable risk factor for the development of suicidal ideation. The Depression-Distress Amplification Model (DDAM) posits that the anxiety sensitivity cognitive concerns (ASCC) subfactor interacts with depressive symptoms to amplify the effects of depression and lead to suicidal ideation. The current study tested the DDAM across the two most widely-replicated factors of depressive symptoms (cognitive and affective/somatic) in comparison to a risk factor mediation model where ASCC are related to suicidal ideation via depressive symptoms. Participants included 295 clinical outpatients from a community clinic. The interaction between ASCC and depressive symptoms in the prediction of suicidal ideation was not significant for either cognitive or affective/somatic symptoms of depression. However, results revealed a significant indirect effect of ASCC through cognitive symptoms of depression in the prediction of suicidal ideation. These cross sectional findings are not consistent with the DDAM. Rather, the relationship may be better conceptualized with a model in which ASCC is related to suicidal ideation via cognitive symptoms of depression.

Suicide risk among male substance users in residential treatment: Evaluation of the depression-distress amplification model

Suicide is a leading cause of death and is significantly elevated among those with substance use disorders (SUDs). However, specific mechanisms of suicide in this population have been relatively understudied. The depression-distress amplification model posits that one pathway to increased suicide risk is through the intensification of depressive symptoms by anxiety sensitivity cognitive concerns. However, this model has not been tested in populations with SUDs. The current study tested the depression-distress amplification model of suicide risk and examined the relation of anxiety sensitivity to suicide risk in a sample of men in residential SUD treatment. Consistent with prior work, anxiety sensitivity cognitive concerns were significantly associated with suicide risk. Moreover, and consistent with the depression-distress amplification model, anxiety sensitivity cognitive concerns related to elevated suicide risk among those with a current major depressive episode specifically, above and beyond insomnia (another risk factor for suicide) and relevant covariates. The results of this study corroborate the relevance of anxiety sensitivity cognitive concerns and the depression-distress amplification model to suicide risk in an at-risk clinical sample of SUD patients. Findings suggest the importance of assessing anxiety sensitivity cognitive concerns and targeting this vulnerability through brief interventions to reduce suicide risk.

Anxiety sensitivity cognitive concerns predict suicide risk

Anxiety sensitivity (AS) cognitive concerns, which reflects fears of mental incapacitation, have been previously associated with suicidal ideation and behavior. The first study aim was to replicate and extend upon previous research by investigating whether AS cognitive concerns can discriminate between those at low risk versus high risk for suicidal behavior. Secondly, we aimed to test the incremental predictive power of AS cognitive concerns above and beyond known suicide risk factors (i.e., thwarted belongingness and insomnia). The sample consisted of 106 individuals (75% meeting current criteria for an Axis I disorder) recruited from the community. Results revealed that AS cognitive concerns were a robust predictor of elevated suicide risk after covarying for negative affect, whereas AS social and physical concerns were not. Those with high, relative to low, AS cognitive scores were 3.67 times more likely to be in the high suicide risk group. Moreover, AS cognitive concerns significantly predicted elevated suicide risk above and beyond relevant suicide risk factors. Results of this study add to a growing body of the literature demonstrating a relationship between AS cognitive concerns and increased suicidality. Incorporating AS cognitive concerns amelioration protocols into existing interventions for suicidal behavior may be beneficial.

Effects of a Single Bout of Aerobic Exercise Versus Resistance Training on Cognitive Vulnerabilities for Anxiety Disorders

The purpose of this study was to compare the relative effects of a single bout of aerobic exercise versus resistance training on cognitive vulnerabilities for anxiety disorders. Seventy-seven participants (60% female; 84% Caucasian) were randomized to complete 20 min of moderate-intensity aerobic exercise, resistance training, or rest, followed by a 35% CO2/65% O2 inhalation challenge task. Results indicated that aerobic exercise and resistance training were significantly and equally effective in reducing anxiety sensitivity (AS) compared with rest ((η(2)(p ) = 52), though only aerobic exercise significantly attenuated reactivity to the CO2 challenge task. Neither form of exercise generated observable effects on distress tolerance, discomfort intolerance, or state anxiety (all ps >.10). The results of this study are discussed with regard to their implications for the use of exercise interventions for anxiety and related forms of psychopathology, and potential directions for future research are discussed.

The depression distress amplification model in adolescents: A longitudinal examination of anxiety sensitivity cognitive concerns, depression and suicidal ideation

Adolescents with comorbid anxiety and depression are at significantly increased risk of suicide. The recently proposed depression distress amplification model appears to have promise for explaining the relations between anxiety, depression, and suicidality, but it has not been tested in adolescents. Participants were 524 adolescents followed over two years. Baseline data for the current report were collected by trained interviewers while the adolescents were in eighth grade. Data were obtained in the same manner when the adolescents were in tenth grade. Baseline anxiety sensitivity cognitive concerns significantly predicted suicidal ideation two years later, above and beyond baseline suicidal ideation and depression. Further, consistent with the depression distress amplification model, anxiety sensitivity cognitive concerns interacted with depressive symptoms to predict suicidal ideation. This report extends the empirical and theoretical support for a relationship between anxiety sensitivity cognitive concerns and suicidality.

The depression distress amplification model in adolescents: A longitudinal examination of anxiety sensitivity cognitive concerns, depression and suicidal ideation

Adolescents with comorbid anxiety and depression are at significantly increased risk of suicide. The recently proposed depression distress amplification model appears to have promise for explaining the relations between anxiety, depression, and suicidality, but it has not been tested in adolescents. Participants were 524 adolescents followed over two years. Baseline data for the current report were collected by trained interviewers while the adolescents were in eighth grade. Data were obtained in the same manner when the adolescents were in tenth grade. Baseline anxiety sensitivity cognitive concerns significantly predicted suicidal ideation two years later, above and beyond baseline suicidal ideation and depression. Further, consistent with the depression distress amplification model, anxiety sensitivity cognitive concerns interacted with depressive symptoms to predict suicidal ideation. This report extends the empirical and theoretical support for a relationship between anxiety sensitivity cognitive concerns and suicidality.

Test of the depression distress amplification model in young adults with elevated risk of current suicidality

Suicide is a leading cause of death among young adults and the rate of suicide has been increasing for decades. A depression distress amplification model posits that young adults with comorbid depression and anxiety have elevated suicide rates due to the intensification of their depressive symptoms by anxiety sensitivity cognitive concerns. The current study tested the effects of anxiety sensitivity subfactors as well as the depression distress amplification model in a very large sample of college students with elevated suicide risk. Participants were 721 college students who were at elevated risk of suicidality (scored>0 on the Beck Scale for Suicide Ideation). Consistent with prior work, anxiety sensitivity cognitive concerns, but not physical or social concerns, were associated with suicidal ideation. Consistent with the depression distress amplification model, in individuals high in depression, anxiety sensitivity cognitive concerns predicted elevated suicidal ideation but not among those with low depression. The results of this study corroborate the role of anxiety sensitivity cognitive concerns and the depression distress amplification model in suicidal ideation among a large potentially high-risk group of college students. The depression distress amplification model suggests a specific mechanism, anxiety sensitivity cognitive concerns, that may be responsible for increased suicide rates among those with comorbid anxiety and depression.

Distress tolerance and anxiety sensitivity cognitive concerns: testing the incremental contributions of affect dysregulation constructs on suicidal ideation and suicide attempt

Empirical work has suggested relationships among suicide-related outcomes and several constructs related to affect dysregulation, notably anxiety sensitivity (AS) and distress tolerance (DT). However, important questions remain, including the relative contributions of these affect regulation variables as well as the direct contribution of DT on suicidal ideation and prior attempts. The current study sought to better elucidate the nature of these relationships by examining AS, DT, and suicidal ideation and attempt in a clinical sample (N=192). Consistent with prior work and prediction, findings revealed a significant relationship between the AS cognitive concerns subfactor and suicidal ideation and suicide attempt history after accounting for the effects of DT, gender, and depressive symptoms. In addition, depressive symptoms significantly moderated the relationship between the AS cognitive concerns subfactor and suicidal ideation. After accounting for the influence of AS, analyses revealed that DT approached significance in predicting suicidal ideation, but did not significantly predict suicide attempt history. These results suggest that elevated AS cognitive concerns are particularly relevant to suicide in the context of depressive symptoms. Clinicians may benefit from implementing AS reduction strategies with individuals who endorse elevated suicide risk as well as elevated AS cognitive concerns.

Hypersensitivity to hypercapnia: definition/(s)

Empirical evidence indicates that panic disorder (PD) patients experience hypersensitivity to hypercapnia, a condition in which the blood level of carbon dioxide exceeds the normal value. The importance of this research line is substantial and indeed, hypercapnic hypersensitivity has been advanced as a possible endophenotype of panic. Definitions of "hypersensitivity," however, have varied. The purpose of this brief review is to delineate and critique different definitions of hypercapnic hypersensitivity. Several definitions - panic attack rate, panic symptoms including dyspnea, subjective anxiety, and respiratory disturbance - are explored. The review concludes that although no ideal definition has emerged, marked anxiety post-hypercapnia has substantial support as a putative trait marker of PD. The term "subjective hypersensitivity" (Coryell et al., 2001) is re-introduced to denote pronounced anxiety post-hypercapnia and recommended for use along with its previous definition: increased self-reported anxiety measured on a continuous visual analog scale, already widely in use. Due to the well-established link between panic and respiration, definitional candidates focusing on aberrant respiratory response - less investigated as trait markers of PD in high risk studies - warrant scrutiny as well. Several reasons why definitional clarity might be beneficial are presented, along with ideas for future research.

Ethnoracial differences in anxiety sensitivity: examining the validity of competing anxiety sensitivity index subscales

Despite the increasing number of Americans who are considered to be a part of an ethnoracial minority group, there have been few investigations of the cross-cultural validity of measures of psychopathology. The limited existing literature suggests potential differences between African American (AA) and European American (EA) individuals with respect to the utility of self-report measures, including anxiety sensitivity. Physical, mental, and social domains of anxiety sensitivity are measured using subscales derived from a 3-factor model reported in EA samples despite evidence suggesting that anxiety sensitivity in AA samples is characterized by more distinct physical concerns. The current study compared the concurrent and predictive validity of the traditional anxiety sensitivity subscales representing 3 domains and a 4-subscale formulation based on predictions about the construct in AA samples. Comparisons of both AA (N=41) and EA (N=298) samples are included. Findings suggest some ethnoracial group differences in the concurrent and predictive validity of anxiety sensitivity subscales, specifically supporting the appropriateness and specificity of the 4-factor model of anxiety sensitivity in AA samples. Implications are discussed, including identification of sociocultural mechanisms that might influence psychometric properties of measures of anxiety.

Biological sex and panic-relevant anxious reactivity to abrupt increases in bodily arousal as a function of biological challenge intensity

An emerging pattern of results from panic-relevant biological challenge studies suggests women respond with greater subjective anxiety than men, but only to relatively abrupt and intense challenge procedures. The current investigation examined the relation between biological sex and self-reported anxious reactivity following biological challenges of varying durations and intensity. Participants were 285 (152 females; M(age) = 21.38; SD = 5.92) nonclinical adults who completed one of three protocols: a 3-min voluntary hyperventilation challenge (VH), a 5-min 10% carbon dioxide-enriched air (CO(2)) challenge, or a 25-s 20% CO(2) challenge. As predicted, results indicated that the 20% CO(2) challenge elicited greater self-reported anxiety than the VH and 10% CO(2) challenges. Moreover, women endorsed greater anxious reactivity than men, but only following the 20% CO(2) challenge. Results are discussed in terms of processes likely to account for sex differences in anxious reactivity following relatively abrupt and intense biological challenges.

The interplay between physical activity and anxiety sensitivity in fearful responding to carbon dioxide challenge

OBJECTIVE

Physical activity may confer protective effects in the development of anxiety and its disorders. These effects may be particularly strong among individuals who have elevated levels of anxiety sensitivity (AS; i.e., the fear of somatic arousal), an established cognitive-based risk factor for anxiety and its disorders. The present study performed a laboratory test of the interplay between physical activity and AS.

METHODS

The participants were adults free of Axis I psychopathology (n = 145) who completed measures of physical activity and AS before undergoing a recurrent 20% carbon dioxide-enriched air (CO(2)) challenge.

RESULTS

Consistent with the hypothesis, physical activity was significantly related to CO(2) challenge reactivity among persons with elevated levels of AS, at high levels of physical activity (p < .001) but not at low levels of physical activity (p = .90). Also consistent with hypothesis, irrespective of the level of physical activity, physical activity did not relate significantly to CO(2) challenge reactivity among persons with normative levels of AS (p = .28).

CONCLUSIONS

These findings provide novel empirical insight into the role that physical activity may play in terms of resiliency for the development of anxiety disorders. Specifically, the protective effects of physical activity may only be evident at higher doses and among persons who are at increased risk of developing anxiety disorders because they have elevated AS.

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.