taVNS to Reduce PTSD Symptoms in WTC Responders

Inclusion Criteria: * being a Queens WTCHP responder who agreed to be contacted to participate in research * having PTSD as per DSM criteria indicated by the GRDC * having elevated PTSD symptoms, indicated by a PCL-S93 score \> 44 during an annual monitoring visit between 2018-2020 * having a score of 33 or greater on the PCL-594 delivered during the initial phone screen to determine current symptomatology * meeting diagnostic indication of PTSD using a Clinician-Administered PTSD Scale (CAPS), which is a clinical interview assessment.95 Exclusion criteria: * being physically/mentally unable to consent and participate * inability to speak, read, or write in English, * exhibiting any current psychotic or manic symptoms, active substance dependence, or current suicidal or homicidal intent/plan, as per the standard MINI neuropsychological assessment.96 * active disease involving the auricle or ear canal (e.g., otitis media, tinnitus, infection, perforated tympanic membrane, vestibular and/or balance, excessive cerumen production, skin irritation), unwilling to remove a piercing (e.g., daith or tragus), or use a device (e.g., hearing aid, cochlear implant) that would preclude daily use of the earpiece. * history of unilateral or bilateral vagotomy. * Current pregnancy (self-report) * previously implanted electrically active medical devices (e.g., cardiac pacemakers, automatic implantable cardioverter-defibrillators, VNS). * other major conditions, that in the judgment of the investigators/WTCHP medical staff, would make the participant unsuitable for inclusion or would interfere with the participant participating in or completing the study. these include: * current treatment with psychotropic medication, including tricyclics, antipsychotics, mood stabilizers, bupropion, barbiturates, stimulants, antiepileptics, opioid medications. * current diagnosis or history of any clinically significant cardiac, endocrinologic, pulmonary, neurologic, psychiatric, hepatic, renal, hematologic, neurologic, gastrointestinal, or immunologic. * history of any of the following cardiovascular conditions: Moderate to severe congestive heart failure (New York Heart Association class III or IV); Recent (within past 6 months) cerebrovascular accident, myocardial infarction, coronary stenting; Uncontrolled hypertension as defined by a confirmed systolic blood pressure \> 160 mmHg or diastolic blood pressure \> 100 mmHg. * history of or active seizure disorder. * history of recurrent vasovagal syncope episodes. * diagnosis of cancer (other than non-invasive skin cancer or carcinoma in-situ of the cervix) within the 5 years prior to study entry. * history of concurrent illness that requires hospitalization within 30 days prior to study entry * have hypertension/hypotension uncontrolled by medication * participation in another investigational trial during the 30 days prior to study entry or during this project