What's interesting about the study that recently came out in Addiction is that it continues the research into clinical manifestations of MDMA use. There is zero doubt that MDMA leaves chemical evidence of its presence in the brain, both neurochemically and physically. Multiple studies have shown discernible differences between non-users' and users' brains.
What matters to users, though, will not be what is happening on a molecular level, but what is happening in a real-life, or "clinical" level. If MDMA users are sustaining damage at the molecular level that never manifests as symptoms, then users can make decisions based on those outcomes. An example can be drawn from the effects of urban living on lung tissue of non-smokers. Autopsies of non-smokers who have lived in medium to large sized cities have lung tissue which is a dark shade of grey as opposed to the light pink of people who lived in rural areas. There is clear molecular damage to the lungs of all city-dwellers, and it is indisputable. However, clinical, real-life consequences of this damage is insignificant to most peoples' lives, spare extreme conditions.
This doesn't that the chemical damage that appears to result from MDMA doesn't cause long-term clinical problems. But it does say that we need more than molecular and imaging studies that show chemical damage by MDMA. We need neurocognitive studies like the study in Addiction that attempts to find real-life results of MDMA use. So far, studies have found either very minor or no change at all. There needs to be more research, of course, but it is telling that after all these years medical research is still unable to show clear, definitive consequences to MDMA use.
This doesn't contradict individual stories of lives ruined by MDMA use. Individual cases will always present themselves, but if they could be demonstrated and reproduced across whole populations of users they would be, and it would be in the medical literature.