After three tours in Iraq and Afghanistan, C. J. Hardin wound up hiding from the world. He had tried almost all the accepted treatments for post-traumatic stress disorder. Nothing worked for me," said Mr. Hardin. Then, in 2013, he joined a small drug trial testing whether PTSD could be treated with MDMA, the illegal party drug better known as Ecstasy. "It changed my life," he said. "It allowed me to see my trauma without fear or hesitation and finally process things and move forward." Based on promising results like Mr. Hardin's, the Food and Drug Administration gave permission Tuesday for large-scale, Phase 3 clinical trials of the drug - a final step before the possible approval of Ecstasy as a prescription drug. The Multidisciplinary Association for Psychedelic Studies, a small nonprofit created in 1985 ... sponsored six Phase 2 studies treating a total of 130 PTSD patients. Two trials ... focused on treating combat veterans, sexual assault victims, and police and firefighters with PTSD who had not responded to traditional prescription drugs or psychotherapy. Patients had, on average, struggled with symptoms for 17 years. After three doses of MDMA administered under a psychiatrist's guidance, the patients reported a 56 percent decrease of severity of symptoms on average, one study found. By the end of the study, two-thirds no longer met the criteria for having PTSD. Follow-up examinations found that improvements lasted more than a year after therapy.