> They are more like nutmeg, sugar, or tea: slightly mood-altering, perhaps.

This line struck me and particularly the mention of tea.

While tea is only slightly mood-altering, the fact that tea was made with boiled water must have had some larger impact given that it reduced the odds of getting a water borne disease. Yes, you could argue that beer/mead etc also had to be boiled but alcohol is a depressant.

The combination of boiled water and a small amount of caffeine being used by a population not used to it must have been a big deal.