This is Part Three of our Psychedelic Science series. Click here for Part One, here for Part Two, and here for Part Four.

Studies of MDMA — often called "ecstasy" or "molly" — suggest the drug could be a valuable tool for treating Post Traumatic Stress Disorder (PTSD), researchers say.

MDMA had a track record of use in couples therapy before it exploded onto the 1980s rave party scene. In 1985 the federal government classified it as a dangerous and illegal “schedule one” drug with "no currently accepted medical use."

But nearly a dozen recent studies of its therapeutic potential are changing attitudes.

"Every single drug we know, from aspirin to ibuprofin, ... could be a poison or could be a medicine, depending on the dosage, depending on the circumstances," says Andrew Feldmár, a psychologist who is leading a Vancouver study into MDMA-assisted psychotherapy.

Feldmár says that while MDMA is often referred to as a psychedelic drug, it's actually not a mind-bending hallucinogen like LSD or psilocybin. Instead, the lab-made compound works as an empathogen — a psycho-active substance that increases the user’s sense of openness, trust and compassion.

"It opens the heart. ... You realize the past is gone, [and] the future is opaque, so there is nothing else but right here, right now," says Feldmár. "It’s not a cognitive thing. You feel it."

Feldmár and others studying MDMA as a treatment for PTSD say there are two main reasons why the therapy seems to work with those who've suffered trauma. First, it fast-tracks bonding between the patient and therapist. Second, like hallucinogenic drugs now being researched, MDMA only appears to require one or two supervised applications, coupled with limited psychotherapy, to alleviate a patient’s symptoms.

"I have worked with people who have been for years on major tranquilizers or major antipsychotics who after one or two MDMA sessions never had to take the ordinary standard pharmaceutical drugs again," said Feldmár.

That proved appealing to former New York City resident Sean (not his real name) who agreed — in exchange for keeping his identity confidential — to tell his story about undergoing illegal but effective MDMA-assisted psychotherapy.

Sean was a 33 year-old construction worker in Manhattan on Sept. 11, 2001. After the terrorist attacks, he rushed to Ground Zero to help search for his colleagues and other victims. Sean ended up staying at the site for six weeks, where he sifted through the debris and fielded daily questions from people desperate for clues about lost loved ones.

"You wanted to be as positive as possible, despite what you saw," he said. "That role stuck with me for a while, and I was never able to truly feel what a strong impact that tragedy had on my life."

Soon, anxiety, depression and night terrors took hold of him and he was diagnosed with PTSD. He says two years of traditional psychotherapy got him nowhere. Then he found a therapist willing to give him MDMA as part of a psychotherapy session. And that's when his life changed.

"I felt a sense of relief, ... a sense of openness," says Sean, adding that during the session, "I was able to start talking about it, walking through my memories of what it was like in a way that I hadn’t been able to do before, without being overcome by emotions."

But such work isn't easy. Despite its street name, ecstasy is anything but euphoric for those, such as Sean, who have taken it to help treat their PTSD, says Rick Doblin, founder of the non-profit group MAPS - the Multidisciplinary Association for Psychedelic Studies.

"But it’s hard in a way that’s productive," Doblin says of MDMA-assisted psychotherapy. "Their fear is reduced; they can express their emotions, they can integrate it, they can learn that the triggers that they had are not always a sign of danger. So they don’t have to constantly be on alert and hyper-vigilant."

Doblin’s group funds MDMA-assisted psychotherapy, including a significant study published in the Journal of Psychopharmacology.

That research involved 20 patients with chronic PTSD from childhood sexual abuse and rape. Most in the study experienced sustained relief of symptoms after undergoing the MDMA treatment.

"We had very strong results," said Dr. Michael Mithoefer of the Medical University of South Carolina, who led the research. "PTSD symptoms went down dramatically in the people that had the therapy with the MDMA compared to people who also improved, but much less, with the therapy alone — without the MDMA," he said.

Mithoefer, a professor of psychiatry, said there is no magic bullet for treating PTSD, but he’s optimistic about MDMA's potential.

"The signs are this may turn out to be a very effective therapy for many people who wouldn’t respond to other things…so the potential is there could be millions of people helped who aren’t being helped now," he said.

Mithoefer is now leading a larger trial into the effect of MDMA-assisted therapy for veterans. If successful, the study will move MDMA one step closer to government approval. And that, he says, could be good news for the estimated 25 million Americans who suffer from PTSD.

MAPS video on using MDMA to treat veterans with PTSD