I think studies like this tend to overlook selection bias. What is typically omitted is that there is some degree of “tolerance” that’s needed to consume modera

I think studies like this tend to overlook selection bias. What is typically omitted is that there is some degree of “tolerance” that’s needed to consume moderately caffeinated beverages. Individuals might avoid these drinks if they feel like they get negative effects (ie anxiety, palpitations, headaches) from them. I know this barely scratches the surface of the uncontrolled factors, but I wanted to throw this point out there.