The Food and Drug Administration (FDA) has approved the use of MDMA in large-scale clinical trials, The New York Times reports, amid emerging evidence that the illegal party drug could be used to treat post-traumatic stress disorder (PTSD).

The Phase 3 research will involve at least 230 patients, the Times reports, and will be funded by the Multidisciplinary Association for Psychedelic Studies (MAPS), an organization that advocates for the medical use of marijuana, LSD, and MDMA (also known as ecstasy). MAPS has already funded six Phase 2 studies of MDMA, involving 130 PTSD patients in total. In one study involving 19 PTSD patients, 56 percent said their symptoms declined in severity after receiving three doses of MDMA; by the end of the study, two-thirds didn’t meet the criteria for having PTSD.

“I’m out of the darkness and the world is all around me.”

The researchers who conducted the study have applied for breakthrough therapy status with the FDA. If their proposal is approved, MDMA could be administered by psychotherapists as early as 2021. But there are concerns that approving the drug for therapeutic use could lead to broader recreational use, in the same way that prescription opioids have.

“It sends the message that this drug will help you solve your problems, when often it just creates problems,” Andrew Parrott, a psychologist at Swansea University in Wales, tells the Times. “This is a messy drug we know can do damage.”

But some who suffer from PTSD see hope in MDMA. Two drugs currently approved to treat PTSD work only slightly better than placebo in trials, and psychotherapy can take a long time to show results.

“I just felt hopeless and in the dark,” C. J. Hardin, a veteran who did three tours in Iraq and Afghanistan, tells the Times. Hardin tells the Times that his PTSD led to alcoholism, divorce, and suicidal thoughts. “But the MDMA sessions showed me a light I could move toward. Now I’m out of the darkness and the world is all around me.”