MDMA-Assisted Therapy for Veterans With Moderate to Severe Post Traumatic Stress Disorder

Inclusion Criteria: * At Screening, meet DSM-5 criteria for current PTSD with a symptom duration of at least 6 months. * Fluent in speaking and reading the predominantly used or recognized language of the study site (English). * Must be a veteran enrolled at a VA Healthcare Center in the Greater Los Angeles area. * Able to swallow pills. * Agree to have study visits audiovisually recorded, including Experimental Sessions, IR assessments, and non-drug therapy sessions. * Able to provide a contact (relative, spouse, close friend, or other support person) who is willing and able to be reached by the investigators in the event of the participant becoming unwell or unreachable. * Able to identify appropriate support person(s) to stay with the participant on the evenings of Experimental Sessions if needed. * May have well-controlled hypertension that has been successfully treated with anti-hypertensive medicines, if they pass additional screening to rule out underlying cardiovascular disease. * May have asymptomatic Hepatitis C virus (HCV) that has previously undergone evaluation and treatment as needed. * Body weight of at least 45 kilograms (kg). Participants with a body weight of 45-48 kg must also have a body mass index (BMI) within the range of 18 to 30 kg/m2. BMI must be within 18 to 32 kg/m2 (inclusive). * A person able to be pregnant (PABP) must use a highly effective contraceptive method. Exclusion Criteria: * Are not able to give adequate informed consent. * Have evidence or history of significant medical or psychiatric disorders. * Are abusing illegal drugs. * Unable or unwilling to safely taper off prohibited psychiatric medication. * Current enrollment in any other clinical study involving an investigational study treatment or any other type of medical research, unless approved by the study clinician.