The first study you cite involves an examination of “ecstasy” users, which makes it fairly useless since pill producers can put anything they want in what is sold as “ecstasy pills”, including known neurotoxins (e.g. methamphetamine).
We won’t really have proper evidence on the neurotoxicity of MDMA unless we can study people whom we know actually ingested MDMA - rather than MDA, speed, 2-CB etc.
Furthermore, neurotoxicity is not inherent to any substance, since it must depend on dosage (I know no substance which is toxic when a single molecule is ingested). Dosage must be a parameter, or the study makes no sense — ingesting 100 grams of table salt will kill you, but we don’t call salt “toxic” because of this.
We won’t really have proper evidence on the neurotoxicity of MDMA unless we can study people whom we know actually ingested MDMA - rather than MDA, speed, 2-CB etc.
Furthermore, neurotoxicity is not inherent to any substance, since it must depend on dosage (I know no substance which is toxic when a single molecule is ingested). Dosage must be a parameter, or the study makes no sense — ingesting 100 grams of table salt will kill you, but we don’t call salt “toxic” because of this.