Move over, marijuana. The FDA will soon begin Phase III clinical trials investigating whether MDMA—the illegal party drug better known as ecstasy—can be used as treatment for post-traumatic stress disorder (PTSD). If successful, the studies could turn yet another illicit substance into a medical therapy, The New York Times reports.

PTSD is a mental illness that some people develop after experiencing or witnessing a life-threatening event or trauma, such as combat, a natural disaster, a fatal accident or a sexual assault. Current treatments for PTSD include one-on-one psychotherapy, group therapy and nearly a dozen different medications, including a number of commonly used antidepressants. But mental health experts say that for up to 40 percent of people with PTSD, current treatments don’t work.

The push to get ecstasy to market as a mental health treatment has been ongoing since at least the 1950s, long before MDMA became a popular party drug. In 1983, the Multidisciplinary Association for Psychedelic Studies began advocating the legal medical use of MDMA as a PTSD therapy. Since then, the nonprofit group has sponsored six Phase II studies—which have treated a total of 130 people with PTSD—on the use of ecstasy for mental health therapy

Findings showed that ecstasy causes the brain to release a flood of chemical substances in the body that evoke feelings of trust, love and well-being while muting fear and negative emotional memories, which can overpower people with PTSD. One recent study on MDMA found that after three doses of the drug (administered under a psychiatrist’s care), people with PTSD who used the med reported a 56 percent decrease in the severity of their symptoms. By the end of the trial, two thirds of the participants no longer met the criteria for PTSD. In interviews, individuals in the study also said MDMA therapy helped them stop abusing alcohol and other drugs and rebuild their lives.

But some scientists expressed worry that FDA approval of the Schedule 1 drug could encourage more people to abuse MDMA for illegal recreational use. When not administered correctly, ecstasy can cause brain damage, overheating, dehydration, loss of consciousness, organ failure and even death. Long-term use of the drug can also eventually lead to depression, anxiety, insomnia and addiction. 

Now that the FDA has approved Phase III clinical trials for MDMA, researchers will test at least 230 additional patients to see how they respond to the drug. Despite the risks, scientists are very optimistic about the studies and have already submitted applications to the agency for MDMA to receive “breakthrough therapy” status. This would speed up the approval process, which could make ecstasy available by prescription in the United States by 2021.

Click here to learn more about post-traumatic stress disorder and its currently available treatments.