BBC News By Rachel Schraer image copyrightGetty Images MDMA - most commonly known as a party drug - could be more effective than therapy alone at treating post-traumatic stress disorder (PTSD). The results of a keenly-awaited trial suggest two-thirds of people no longer qualified for a PTSD diagnosis after treatment. The study represents a significant step towards approval of the drug in the US. But UK experts warn against overhyping MDMA's potential, saying more research is needed to understand its effects. PTSD can be the result of a very distressing or frightening event, or longer-term series of experiences. That might include accidents, abuse, rape, combat or illness.