Well, yeah. The studies were all longitudinal studies relying on self-reporting and some found an increased risk for >5 cups per day. Since a ”cup” is not a well defined measurement anyway, these are not very rigorous studies. It’s baffling that scientists so readily interpret these results to mean something, when it’s infinitely more likely they’ve missed some unexpected confounders.

I found no mention of MAO inhibitors, beta-carbolines or heterocyclic aromatic amines in coffee. The authors seem to be unaware of their existence, even though they could explain the results in many ways.