In July, the Food and Drug Administration took the important step of approving two final-phase clinical trials to determine whether a party drug that has long been on the Drug Enforcement Administration's Schedule I list of banned substances could be used to treat a psychiatric condition that afflicts millions. The drug is MDMA, a psychedelic commonly known as Ecstasy. The trials aim to determine whether the drug is, as earlier trials have suggested, a safe and effective treatment for post-traumatic stress disorder. The F.D.A. approval is a beacon of hope for the roughly eight million Americans believed to suffer from PTSD, a group that includes victims of abuse, refugees and combat veterans. The shortcomings in the way we have typically treated PTSD mean that many are condemned to suffer from the condition for years, even decades, with little relief. Less than 20 percent of patients are estimated to get effective treatment through prescription psychiatric drugs ... which, along with psychotherapy, have been the global standard of mental health care since the 1990s. This could change with the F.D.A.'s decision, which has given MDMA-assisted psychotherapy for the treatment of PTSD the status of a potential "breakthrough therapy." This designation permits the fast-tracking of trials in hopes of proving the drug, which has psychedelic and stimulant effects, to be safe and capable of doing what no other drug on the market can.