MDMA (also known as ecstasy in pill form or molly in crystal form) is a drug that acts as a stimulant and has some psychedelic effects. It can cause increased energy, enhanced sensations, emotional closeness, and feelings of pleasure. People typically feel its effects about 30 to 45 minutes after taking it, and those effects last between three and six hours. MDMA has also been studied as a possible aid in therapy, especially for conditions like PTSD and social anxiety in people with autism.