Around 7 people die out of every million that use MDMA. Mostly this is due to overheating and dehydration. However, it is possible to drink too much water, swelling the brain and causing death. Many people have died from this after taking MDMA. Another factor is the hormone vasopressin, which is released during MDMA use. Vasopressin restricts the body's urge to urinate, which helps to get rid of excess liquid in the body before it becomes a problem.