Evaluation of MDMA on Startle Response

Inclusion Criteria: * Persons aged 21 to 55. * Ability to visually read and understand English language. * Live within in metro Atlanta area * Previously used MDMA in a recreational or research setting * If a person is of childbearing potential (able to bear children), they must have a negative pregnancy test at study entry and prior to the Experimental Session. They must agree to use adequate birth control through 10 days after the last dose of MDMA. Adequate birth control methods include intrauterine device (IUD), injected or implanted hormonal methods, abstinence, oral hormones plus a barrier contraception or double barrier contraception. Two forms of contraception are required with any barrier method or oral hormones (i.e. condom plus diaphragm, condom or diaphragm plus spermicide, oral hormonal contraceptives plus spermicide or condom). Not of childbearing potential is defined as permanent sterilization, postmenopausal, or male. * (For sub-study measuring serum oxytocin) Willing to have periodic blood draws Exclusion Criteria: * Upon review of medical or psychiatric history, have any current or past diagnosis that would be considered a risk to participating in the study. * Are abusing illegal drugs. * Current use of any psychoactive medications, including antidepressants, mood stabilizers, sedatives, stimulants, antipsychotics, anxiolytics, or beta-blockers * Are not able to give adequate informed consent. * Uncontrolled hypertension, or clinically significant cardiac arrhythmia, as detected by electrocardiogram. * Currently pregnant or breast-feeding. * History of acute angle glaucoma. * Hearing impairment as assessed by audiometer; unable to detect tones below 40 dB in right or left ear.