Anxiety disorders affect over a quarter of the population, yet very little is known about the variables that predict treatment outcome. The planned study explores whether a patient's response to a physiological test involving inhalation of carbon dioxide predicts their response to exposure therapy.

Anxiety Sensitivity (AS) refers to an individual's fear of experiencing anxiety-related symptoms (e.g., dyspnea or heart palpitations) and is a core construct underlying the initiation and maintenance of pathological anxiety. Recent evidence suggests that reducing AS may be critical for the prevention and treatment of anxiety across diagnostic categories. Exposure therapy, an important component of cognitive behavioral therapy (CBT), is one of the most effective treatments for reducing AS, and has been shown to improve symptoms across a number of different anxiety disorders. Meta-analyses reveal an approximately 50% treatment response rate, with the remaining half of patients showing either no response or dropping out of treatment early. Unfortunately, there is a paucity of research exploring which variables predict treatment outcome and there are currently no tests for predicting which patients would benefit the most from exposure therapy. In this study, participants will complete two sessions of a carbon dioxide (CO2) habituation paradigm, a safe and noninvasive physiological test that entails repeated exposures to single vital capacity inhalations of 20% CO2. Both CO2 testing sessions will be completed within a 72-hour time period. Patients then complete a 10-week group-based exposure therapy to determine whether an individual's degree of habituation to CO2 predicts treatment outcome.

Inclusion Criteria:

1. DSM-V diagnosis of an Anxiety disorder (Generalized Anxiety Disorder, Social Anxiety Disorder, Panic Disorder, Agoraphobia)
2. Anxiety Sensitivity Index (ASI-3) total score > 29
3. Overall Anxiety Severity and Impairment Scale (OASIS) score > 8
4. Between 18-55 years of age
5. Subject must be "treatment-seeking" and willing to enroll in the 10-week group-based Exposure Therapy

Exclusion Criteria:

1. Comorbid Bipolar Disorder, Schizophrenia, Anorexia or Bulimia Nervosa, or Obsessive-Compulsive Disorder
2. Current Substance Use Disorder > moderate (within the past 6 months)
3. Currently taking a psychotropic medication
4. Currently receiving psychotherapy/counseling for anxiety
5. Currently being treated as an inpatient
6. Active suicidal ideation with intent or plan
7. History of neurological, cardiovascular or respiratory problems (e.g., asthma, severe brain injury)