The news article makes it sound like causation has been determined beyond a doubt but the actual study abstract does not detail why the authors think this. Is it impossible to imagine that more brain “damage” leads to more drinking in some cases? Do people who are developing Alzheimer’s sometimes drink more to feel better?

Also not clear is the selection criteria. Are these people who were going to have an MRI and incidentally were offered a chance to participate in this study? In that case it could have biased the sample - there could be a large group of people drinking alcohol and being just fine but they wouldn’t be seen in this study for the very reason that they are doing fine and weren’t getting MRIs.

Certainly the presented hypothesis could be true but the article would be more convincing if it was more critical of its source material. Correlations are easy, they’re a dime a dozen. Proving causation is the real work.