So the levels of neurotoxicity for MDMA are not known. It's almost certainly neurotoxic to some degree but not any where near the levels purported by that study

So the levels of neurotoxicity for MDMA are not known. It's almost certainly neurotoxic to some degree but not any where near the levels purported by that study that used massive amounts of meth on rats (remember alcohol is also neurotoxic). However, over use can certainly habituate a user to it such that it "loses its magic" as in the psychoactive effect is far far far less than what it originally was.