Yes the JACN article is at least a scientific study. It is one data point however, and AFAIK the only study to find a link between soy intake and decreased cogn

Yes the JACN article is at least a scientific study. It is one data point however, and AFAIK the only study to find a link between soy intake and decreased cognition -- compared with a large body of research that has associated intake of soy isoflavones with better health, including better cognition. These include studies of typical Asian diets, which are known to be higher in soy than Western diets. If one was to look at the entire scientific literature honestly and soberly, I think the evidence would overwhelmingly support the claim for soy health benefits.