MDMA can induce euphoria, a sense of intimacy with others, diminished anxiety, and mild psychedelia. Many studies, particularly in the fields of psychology and cognitive therapy, have suggested MDMA has therapeutic benefits and facilitates therapy sessions in certain individuals, a practice for which it had been formally used in the past. Clinical trials are now testing the therapeutic potential of MDMA for post-traumatic stress disorder, anxiety associated with terminal cancer^[4][5] and addiction.^[6]

MDMA is criminalized in most countries. Some limited exceptions exist for scientific and medical research. For 2008, the UN estimated between 10 and 25 million people globally used MDMA at least once in the past year. This was broadly similar to the number of cocaine, amphetamine, and opioid users, but far fewer than the global number of cannabis users.^[7] It is taken in a variety of contexts far removed from its roots in psychotherapeutic settings, and is commonly associated with dance parties (or "raves") and electronic dance music.^[8]

Regulatory authorities in several locations around the world have approved scientific studies administering MDMA to humans to examine its therapeutic potential and its effects

MDMA has been indicated as possibly useful in psychotherapy, facilitating self-examination with reduced fear.^[10][11][12] Indeed, some therapists, including Leo Zeff, Claudio Naranjo, George Greer, Joseph Downing, and Philip Wolfson, used MDMA in their practices until it was made illegal. George Greer synthesized MDMA in the lab of Alexander Shulgin and administered it to about 80 of his clients over the course of the remaining years preceding MDMA's Schedule I placement in 1985. In a published summary of the effects,^[13] the authors reported patients felt improved in various mild psychiatric disorders and experienced other personal benefits, especially improved intimate communication with their significant others. In a subsequent publication on the treatment method, the authors reported one patient with severe pain from terminal cancer experienced lasting pain relief and improved quality of life.^[14] In the United States, no research on MDMA was allowed at all, from 1985 until 1992, when the FDA approved Dr. Charles Grob to conduct human studies.^[15]

In the year 2000, Doctor Jose Carlos Bouso performed the first clinical trial of MDMA for use in treating Post Traumatic Stress Disorder.^[16] Since 2009, two randomized, controlled trials of MDMA-assisted psychotherapy for post-traumatic stress disorder were published. The positive effects were so large as to achieve statistical significance in spite of the small size of the trials (In one study, the rate of clinical response was 10/12 (83%) in the active treatment group versus 2/8 (25%) in the placebo group. In the other study, a p-score of 1.4% was found for the PDS scale and 1.6% for the CAP scale one year after treatment. A p-score of 5% or less is often considered statistically significant, and the effect found needs to be larger with smaller studies to have statistical significance, ceteris paribus, in order to correct for sample size.) In the second study, positive effect in CAP scale immediately after treatment did not achieve statistical significance (p=6.6%), but may do so with a larger sample size. The patients treated with two or three sessions of MDMA-psychotherapy showed greater improvement than the ones treated by placebo-psychotherapy^[17] or placebo-inactive dose of MDMA.^[18] This improvement was generally maintained on a follow-up several years later.^[19]