In an important step toward medical approval, MDMA, the illegal drug popularly known as Ecstasy or Molly, was shown to bring relief to those suffering from severe post-traumatic stress disorder when paired with talk therapy. Of the 90 people who took part in the new study, which is expected to be published later this month in Nature Medicine, those who received MDMA during therapy experienced a significantly greater reduction in the severity of their symptoms compared with those who received therapy and an inactive placebo. Two months after treatment, 67 percent of participants in the MDMA group no longer qualified for a diagnosis of PTSD, compared with 32 percent in the placebo group. MDMA produced no serious adverse side effects. Some participants temporarily experienced mild symptoms like nausea and loss of appetite. Unlike traditional pharmaceuticals, MDMA does not act as a band-aid that tries to blunt symptoms of PTSD. Instead, in people with PTSD, MDMA combined with therapy seems to allow the brain to process painful memories and heal itself. Scott Ostrom, who participated in the study, had suffered from PTSD since returning home from his second deployment in Iraq in 2007. For more than a decade, he experienced debilitating nightmares. Mr. Ostrom's days were punctuated by panic attacks, and he dropped out of college. Therapy and medication did not help. But after participating in the trial, he no longer has nightmares. "Literally, I'm a different person," he said.