Actually nowhere near enough research has been done to understand what, if any, long-term damage frequent MDMA use can cause. In the very short-term it is quit

Actually nowhere near enough research has been done to understand what, if any, long-term damage frequent MDMA use can cause. In the very short-term it is quite neurotoxic, and consuming too much can cause immediate problems. It looks like short-term problems can be minimised by taking a few weeks in between uses, and according to at least one study it looks like all damage can be undone by just a few months of abstience. However there's really not enough data about lasting affects, if there are any, or about how frequency of use could impact your brain's outcome, or.... etc. Anecdotally I've heard many stories of people using MDMA too often and "losing the magic", that it just stops giving them the effects they used to enjoy. One other thing to note, you wrote "if you keep taking it, it will stop working altogether eventually, regardless of an increased dose" I'm no expert, and could well be corrected on this, but I suspect that is much more the case with the positive effects than with the downsides. For example MDMA is a drug known to have a "sweet spot" for most people, unlike many drugs (from booze to weed to cocaine) where different people build up different tolerances/preferences and therefore have a large range of doses, MDMA is generally thought to have quite a small range of good doses, after which increases will cause more/worse side affects without adding anything positive to the experience. Edit: https://dancesafe.org/drug-information/is-mdma-neurotoxic/ https://dancesafe.org/drug-information/is-mdma-neurotoxic/ is good for brief further reading (good sources cited at the end to follow), as well as https://www.erowid.org/chemicals/mdma/mdma_neurotoxicity1.shtml https://www.erowid.org/chemicals/mdma/mdma_neurotoxicity1.sh...