Inclusion Criteria:  English speaking Non-treatment-seeking community members who do not have a mental health diagnosis and individuals seeking treatment for an anxiety, mood, trauma-related, or obsessive-compulsive disorder. Treatment and non-treatment-seeking community members with anxiety, mood, trauma-related, or obsessive-compulsive disorder or symptoms.  Exclusion Criteria:  Diagnosis of COVID-19 in the past 14 days Facial or ear pain or recent ear trauma Metal implant devices in the head, heart or neck History of brain stimulation or other brain surgery History of myocardial infarction or arrhythmia, bradycardia Use of B-blockers, antiarrhythmic medication (sodium/potassium/calcium-channel blockers), or blood pressure medications. Active respiratory disorder Personal or family history of seizure or epilepsy or personal use of medications that substantially reduce seizure threshold (e.g., olanzapine, chlorpromazine, lithium). Personal history of head injury, concussion, or self-report of moderate to severe traumatic brain injury Individuals suffering from frequent/severe headaches Individuals with lifetime evidence of severe psychiatric disorder (e.g., schizophrenia) or neurological disorder. Moderate to severe alcohol or substance use disorder. Pregnancy