CO2 Reactivity as a Biomarker of Non-Response to Exposure-Based Therapy

This study is investigating whether how your body responds to changes in carbon dioxide levels can predict how well you'll respond to exposure-based therapy for anxiety disorders such as panic disorder, social anxiety, OCD, PTSD, or generalized anxiety disorder. **You may be eligible if...** - You have been diagnosed with panic disorder, social anxiety disorder, generalized anxiety disorder, OCD, or PTSD - You score 8 or higher on a standard anxiety severity scale - You are between 18 and 70 years old - You are proficient in English **You may NOT be eligible if...** - You have a history of bipolar disorder, psychosis, or a substance use disorder (other than nicotine) - You have active thoughts of suicide with intent to act - You have a medical condition that makes CO2 inhalation unsafe (heart arrhythmia, asthma, epilepsy, high blood pressure, or stroke history) - You are pregnant or breastfeeding - You are currently in therapy for your anxiety condition - You recently started a new psychiatric medication (within the past 8 weeks) Talk to your doctor to see if this trial is right for you.