These studies get emphasized by MDMA proponents because they find them easiest to argue against.

Many of the arguments are based on flawed logic, like taking rat mg/kg numbers and translating directly to human mg/kg numbers. This isn't how drugs are scaled to animal doses (see https://pmc.ncbi.nlm.nih.gov/articles/PMC4804402/ if you want to understand) so it leads to a lot of claims that studies are giving insane doses when they may not be.

Honestly this game isn't my favorite because someone always comes along to point out why various studies aren't 100% perfect in humans with a large sample size and then tries to suggest that therefore it should all be ignored. If they can't attack the study, they attack the motivations of the authors or insert claims like how the sample group may have been taking other drugs. If that fails, they try to claim that the drug users may have had those deficits to begin with, which led to the drug use. It goes on and on.

Here's one random study where abstinent users had decreased memory scores. The decrease scaled relative to how much of the drug they recalled using: https://pubmed.ncbi.nlm.nih.gov/9855498/ (Opponents will point out one of the authors is hated in the drug community due to past controversy and therefore they won't trust the study)

Here's another one where ex-users showed verbal memory deficits, among other things: https://pubmed.ncbi.nlm.nih.gov/16510479/

It's honestly not hard to find studies like this, but what you won't find is big placebo-controlled gold standard trials with enough dosing to achieve statistical significance. That's because it's not ethical to do so, and therefore it won't happen.

In https://pubmed.ncbi.nlm.nih.gov/9855498/ the average dose was a staggering 440mg a month (multiple rolls a month) with a sample size of 24 people. This is definitely falls under "heavy" usage and even then it's hard to disambiguate correlation vs causation in such a small, underpowered study.

The average participant in your second study, https://sci-hub.ru/10.1177/0269881106059486, had again taken an average of 800 lifetime doses. These are insane amounts and do not remotely reflect the average user.

Here's a meta study for example that found no long term impact among more realistic users - https://pmc.ncbi.nlm.nih.gov/articles/PMC3053129. I haven't looked into this in a long time, so I ran a deep research query, and for typical usage (<50 lifetime doses, months between sessions) there seems to be very little evidence of structural or functional harm.

[1] https://chatgpt.com/s/dr_6817cd9ce85081918c7d55fa9a28c654

You have to agree the presented studies are very far from 100% perfect, you just chose to believe them. That is your choice but you shouldn't force this choice on others.

> what you won't find is big placebo-controlled gold standard trials with enough dosing to achieve statistical significance

Would they be really needed if MDMA really was the killer drug you are making it to be? Because for alcohol (or heroin) abuse it's not that hard to get statistical significance from observation studies on population - a combination of large number of people abusing alcohol and its large negative effects. Where are similar studies for MDMA proving your claims?

I'd imagine such a study would be quite difficult because so many things could affect your results: sleep, diet, age, alcohol, covid, etc.

I know nothing about this but I feel like the technology exists to scan your brain before and after to see neuron damage. I just want to know if a single use causes permanent brain damage and to what extent.