The US Food and Drug Administration has given its approval on Tuesday for a large-scale, Phase III clinical trial of MDMA, more popularly known as Ecstasy, as a prescription medication, potentially for the treatment of post-traumatic stress disorder, a common condition in soldiers sent to war-stricken countries, such as Iraq and Afghanistan.

Behind the push to legalize the medical use of Ecstasy is the non-profit organization Multidisciplinary Association for Psychedelic Studies (MAPS). It has already sponsored six Phase II clinical trials, treating 130 PTSD patients with the controversial substance. MAPS is also in favor of legalizing other banned substances - including marijuana and LSD - for its medicinal benefits.

"Our Phase 2 study has treated 136 people, and Phase 3 will involve 200-400 subjects with PTSD from all sorts of causes across the U.S., Canada, and a lot of different countries. Phase 3 starts around 2017, and it will take four to five years to finish. So that will put it at early 2021 for FDA approval, MAPS Director Brad Burge told Inverse in an article back in March.

Burge also cited the other groups that could possibly benefit from Ecstasy.

"So far we've looked at PTSD in everyone. We've had one trial in the long term, that's now in the one year follow-up date with primarily veterans, as well as with police officers and fire fighters who were first responders at 9/11. So that study also involved the army, the marines, air force, all sorts of military groups who had served in Afghanistan, Iraq, Vietnam and Korea. The other major group of people were female survivors of sexual abuse or assault," she shared.

"Phase 3 starts around 2017, and it will take four to five years to finish. So that will put it at early 2021 for FDA approval," Burge added.

On the issue of ecstasy's bad reputation as an illicit party drug linked to substance abuse and even death, an FDA spokesperson refused to give further details because of the agency's stringent non-disclosure guidelines on drugs currently being developed,

However, Dr. Charles R. Marmar, the head of psychiatry at New York University's Langone School of Medicine, a leading PTSD researcher who was not involved in the study, expressed his concerns.

"I'm cautious but hopeful. If they can keep getting good results, it will be of great use. PTSD can be very hard to treat. Our best therapies right now don't help 30 to 40 percent of people. So we need more options," he told the New York Times.

"It's a feel-good drug, and we know people are prone to abuse it. Prolonged use can lead to serious damage to the brain," he warned.