Stanford Regulating Circuits of the Brain Study - MDMA

Inclusion Criteria: 1. Ages 18-55 2. Able to swallow capsules 3. All genders and ethno-racial categories 4. Able and willing to enroll and provide written informed consent. 5. Able to comply with study procedures. 6. 2+ prior uses of MDMA when aged 18 years or older and have reported no serious adverse reactions from MDMA or ecstasy. 7. Non-nicotine user, defined as no primary nicotine exposure for last six months. 8. Agree to not use caffeine for 12 hours before and 10 hours after drug administration. 9. Not using any medication or substance that might increase the risk of participation and/or interact with MDMA (i.e., serotonergic agents, antidepressants, opiates, any drugs with known interactions with Monoamine Oxidase Inhibitors). 10. Must agree to inform the investigators within 48 hours of any changes in medical conditions or procedures. 11. If of childbearing potential, must have a negative pregnancy test at study entry and prior to each drug session and must agree to use adequate birth control through 10 days after the last drug session. Adequate birth control methods include intrauterine device (IUD), injected or implanted hormonal methods, abstinence, oral hormones plus a barrier contraception, vasectomized sole partner, or double barrier contraception. Two forms of contraception are required with any barrier method or oral hormones. 12. Able to receive an MRI. Exclusion Criteria: 1. Have current serious suicide risk, as determined through psychiatric interview, responses to C-SSRS, and clinical judgment of the investigator. 2. Current psychiatric, mood, anxiety, eating or psychotic disorder assessed at screening with the MINI and medical history. 3. Current use of any psychotropic medication (a wash-out period of 5 half-lives will be required prior to drug visits followed by a 1-week stabilization period, if the participant reports recently discontinuing a psychotropic medication). 4. Have used Ecstasy (material represented as containing MDMA) within 6 months of the first study dose; or have previously participated in a MAPS-sponsored MDMA clinical trial. 5. Positive for drug, or alcohol abuse disorders as assessed through DAST, CUDIT-R, Fagerstrom and AUDIT measures. 6. Positive test on urine drug screen for illicit and/or drugs of abuse at screening and prior to study drug administration. 7. Concurrent use of any medication or substance that might increase the risk of participation and/or interact with MDMA (i.e., serotonergic agents, antidepressants, opiates, any drugs with known interactions with Monoamine Oxidase Inhibitors). 8. Unable or unwilling to agree to refrain from using any psychoactive substances (i.e., cannabis), supplements (i.e., St. John's Wort, SAMe, 5HTP) and nonprescription medications (i.e., dextromethorphan) starting 1-week prior to study start and for duration of study. 9. Current use of any opioids, including codeine, hydrocodone, and morphine. 10. Have an exclusionary metal device (e.g., presence of metallic device or dental braces, which are contraindications for MRI) as determined by the discretion of the Clinical Investigator. 11. BMI outside of healthy range (18-30) 12. Inability to speak, read or understand English at a 5th grade level or severe hearing impairment. 13. Plan to move out of the area during the study period (given repeated testing sessions) 14. Individuals who are pregnant or nursing. 15. Schizophrenia in a first degree relative. 16. Direct physical access to or routinely handling of addicting drugs in the regular course of work duties. 17. Allergy or hypersensitivity to MDMA 18. Renal/hepatic impairment (assessed via laboratory tests during initial screening appointment) 19. Hypertension (Hypertension, Stage 1 as defined by a systolic blood pressure \>140 mmHg or diastolic blood pressure \> 90 mmHg on two of three measurements at least 15 minutes apart at initial screening appointment; systolic blood pressure \>155 mmHg or diastolic blood pressure \>99 mmHg on two of three measurements at least 15 minutes apart during drug administration visits) 20. Heart rate \<50bpm or \>150bpm assessed at initial screening visit (PI discretion for bradycardia) 21. Chronic congestive heart failure, tachyarrhythmias, myocardial ischemia (assessed via EKG at initial screening appointment) 22. Have a marked Baseline prolongation of QT/QTc interval e.g., repeated demonstration of a QTc interval \>450 milliseconds (ms) in males and \>460 ms in females. For transgender or non-binary participants, QTc interval will be evaluated based on sex assigned at birth, unless the participant has been on hormonal treatment for 5 or more years. 23. Have evidence or history of significant (controlled or uncontrolled) hematological, endocrine, cerebrovascular, cardiovascular, coronary, pulmonary, renal, gastrointestinal, immunocompromising, or neurological disease, including seizure disorder, or any other medical disorder judged by the investigator to significantly increase the risk of MDMA administration (participants with hypothyroidism who are on adequate and stable thyroid replacement will not be excluded). Note: if participants present with a history of glaucoma, enrollment would be allowed only with the approval of their ophthalmologist. 24. Have a history of additional risk factors for Torsade de pointes (e.g., heart failure, hypokalemia, family history of Long QT Syndrome) 25. Have history of hyponatremia or hyperthermia