I didn't really mean it as a "rebuttal", as the paper is careful about not claiming any causal link. I meant it as a warning to the reader to be careful about

I didn't really mean it as a "rebuttal", as the paper is careful about not claiming any causal link. I meant it as a warning to the reader to be careful about drawing conclusions like that. To establish causation you'd need a study where alcohol consumption of the subjects is controlled by the experimenters. That would eliminate the effect of confounding factors that influence both alcohol consumption and cognitive function.