Ecstasy/Molly are MDMA.
Basically, MDMA activates a part of your brain which releases serotonin and that part is like a bank or a “holding space” of serotonin. Serotonin is also released when we eat chocolate, have sex or do something fun we enjoy and get that “happy feeling”.
When someone takes MDMA they release almost all of the serotonin in their bank, so it feels good and you have a great time because serotonin. Thing is, serotonin takes time to fill back up in the bank.
MDMA also acts as a psychedelic drug (a drug that can induce hallucinations or the feeling of expanded consciousness).
When people take MDMA regularly; like twice in a week or more, they don’t have the serotonin to enhance their “psychedelic experience”. So what was at one time this amazing, euphoric experience of feeling one with others and empathetic can turn into a nightmare where people feel they can’t escape it, until the effects ware off.
Some studies suggest long term regular use can cause long term permanent problems with serotonin regeneration.
Using pure/good MDMA occassionally (once/twice a year, spaced out from months apart) shouldn’t cause problems. Using it regularly can result in depression and possible brain damage due to serotonergeic damage.