MDMA-Assisted Cognitive-Behavioral Conjoint Therapy (CBCT) in Dyads in Which 1 Member Has Chronic PTSD

Inclusion Criteria: * All inclusion criteria for the PTSD and Concerned Significant Other (CSO) are identical except for first two items, marked below: * PTSD+ participant: Meet DSM-5 criteria for current PTSD and satisfies PTSD criteria via CAPS * CSO participant: Meet criteria for V62.89 Other Problem Related to Psychosocial Circumstances under Diagnostic and Statistical Manual 5 (DSM-5), as determined through clinical interview, for current psychosocial circumstances contributing to relationship distress with intimate or non-intimate partner * Are at least 18 years old * If in psychotherapy, willing and able to maintain that schedule without changing it * Are willing to refrain from taking any psychiatric medications during the study period, with the exception of gabapentin when prescribed for pain control. * Willing to remain overnight at the study site * Are willing to be driven home the morning after the experimental sessions, after the integrative therapy session * Are willing to commit to medication dosing, experimental sessions, follow-up sessions, to complete evaluation instruments and commit to be contacted for all necessary telephone contacts * Are willing to remain overnight at the study site after each experimental session until after the integrative session occurring the next morning * Must have a negative pregnancy test at study entry and prior to each experimental session if able to bear children, and must agree to use adequate birth control through 10 days after the last dose of MDMA. * Must provide a contact (relative, spouse, close friend or other caregiver other than the CSO participant) who is willing and able to be reached by the Clinical Investigators in the event of a participant becoming suicidal. * Must agree to inform the Clinical Investigators within 48 hours of any medical conditions and procedures * Are proficient in speaking and reading English * Agree to have all clinic visit and Integrative Sessions recorded to audio and video * Agree to not participate in any other interventional clinical trials during the duration of this study Exclusion Criteria: * The following exclusions are identical for PTSD+ and CSO participants except for the following, marked below: * CSO participant only: Have diagnosis of current PTSD not in remission * Are pregnant or nursing, or are women of child bearing potential who are not practicing an effective means of birth control * Have evidence or history of significant medical disorders * Have hypertension * Have liver disease; asymptomatic participants with Hepatitis C who have previously undergone evaluation and successful treatment is permitted. * History of hyponatremia or hyperthermia * Weigh less than 48 kg * Have used "Ecstasy" (material represented as containing MDMA) more than 10 times within the last 10 years or at least once within 6 months of the MDMA-assisted session * Are not able to give adequate informed consent